TABLE OF CONTENTS

1. INTRODUCTION 1-1 1.1 Objective 1-1 1.2 Background 1.3 Standard Test Method Development 1-5 1.4 Appliance Energy Efficiency 1-6 1.5 Gas/Electric Consumption Ration 1-8 1.6 Ventilation Requirements 1-11 1.7 Emissions From Commercial Cooking 1-19 1.8 Conclusions 1-23 1.9 References 1-24

2. FRYER 2-1 2.1 Introduction 2-1 2.2 Cooking Processes 2-2 2.3 Types of Fryers 2-2 2.4 Controls 2-3 2.5 Heating Technologies 2-3 2.6 Fryer Performance 2-6 2.7 Benchmark Energy Performance 2-9 2.8 Fryer Energy Consumption 2-13 2.9 Research Needs 2-19 2.10 Gas Industry Market Focus 2-20 2.11 References 2-20

3. GRIDDLE 3-1 3.1 Introduction 3-1 3.2 Cooking Processes 3-2 3.3 Types of Fryers 3-2 3.4 Control Strategies 3-4 3.5 Heating Technologies 3-5 3.6 Griddle Performance 3-9 3.7 Benchmark Energy Performance 3-11 3.8 Griddle Energy Consumption 3-14 3.9 Ventilation Requirements 3-18 3.10 Research Needs 3-18 3.11 References 3-19

Technology Review of Conuncrcial Foodservice Equipment Volume II, Page i 4. BROILER 4-1 4.1 Introduction 4-1 0 4.2 Cooking Processes 4-2 4.3 Controls 4-2 4.4 Types of Fryers 4-3 4.5 Broiler Performance 4-8 4.6 Ventilation Requirements 4-10 4.7 Research Needs 4-11 4.8 Gas Industry Market Focus 4-12 4.9 References 4-13

5. RANGE 5-1 5.1 Introduction 5-1 5.2 Cooking Processes 5-2 5.3 Controls 5-2 5.4 Heating Technologies 5-3 5.5 Advanced Technologies 5-5 5.6 Range Top Performance 5-8 5.7 Benchmark Energy Efficiency 5-9 5.8 Range Top Energy ConsumptioConsumption 5-10 5.9 Ventilation Requirements 5-13 5.10 Research Needs 5-10 5.11 Gas Marketing Focus 5-13 5.12 References 5-13

6. CHINESE RANGE/WOK 6-1 6.1 Introduction 6-1 6.2 Cooking Processes 6-3 6.3 Controls 6-3 6.4 Heating Technologies 6-3 6.5 Types of Chinese Ranges 6-4 6.6 Chinese Range Performance 6-5 6.7 Research Needs 6.8 References 6-7

7. OVEN 7-1 7.1 Introduction 7-1 7.2 Cooking Processes 7-2 7.3 Types of Ovens 7-3

Technology Review of Commercial Foodservice Equipment Volume 11. Page ii 7. OVEN (continued) 7.4 Oven Performance 7-13 7.5 Benchmark Energy Efficiency 7-14 7.6 Oven Energy Consumption 7-16 7.7 Ventilation Requirements 7-17 7.8 Research Needs 7-20 7.9 Gas Marketing Focus 7-20 7.10 References 7-20

8. COMPARTMENT STEAMER 8-1 8.1 Introduction 8-1 8.2 Cooking Processes 8-2 8.3 Types of Compartment Steamers 8-2 S.4 Controls 8-3 8.5 Compartment Steamer Performance 8-4 8.6 Benchmark Energy Efficiency 8-7 8.7 Energy Consumption 8-7 8.8 Ventilation Requirements 8-10 8.9 Research Needs 8-10 8.10 References 8-11

STEAM KETTLE 9-1 9.1 Introduction 9-1 9.2 Cooking Process 9-2 9.3 Types of Kettles 9-2 9.4 Advanced Steam Kettle Technology 9-3 9.5 Controls 9-4 9.6 Steam Kettle Performance 9-4 9.7 Benchmark Energy Efficiency 9-6 9.8 Steam Kettle Energy Consumption 9-6 9.9 Ventilation Requirements 9-6 9.10 Research Needs 9-8 9.11 Gas Industry Market Focus 9-8 9.12 References 9-8

10. BRAISING PAN 10-1 10.1 Introduction 10-1 10.2 Braising Pan Performance 10-2 10.3 Benchmark Energy Efficiency 10-3 10.4 Energy Consumption 10-3

Technology Review of Commercial Foodservice Equipment Volume II, Page iii BRAISING PAN (continued) 10.5 Ventilation Requirements 10-5 10.6 Research Needs 10-5 3 10.7 Gas Industry Market Focus 10-6 10.8 References 10-6

11. BIBLIOGRAPHY 11-1

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Technology Review of Commercial Foodservice Equipment Volume II, Page iv LIST OF TABLES

Table 1-1 Appliance Categories and Types 1-1

Table 1-2 Benchmark Cooking-Energy Efficiency Summary 1-9

Table 1-3 AGA Published Gas/Electric Energy Ratio 1-10

Table 1-4 Gas/Electric Energy Consumption Ratios 1-11

Table 1-5 Typical Minimum Exhaust Flow Rates for Listed Hoods by Cooking Equipment Type 1-18

Table 2-1 Energy Efficiency for 18-22 kg (40-50 lb) Capacity Open Deep-Fat Fryers 2-10

Table 2-2 Energy Efficiency for 14-22 kg (30-50 lb) Capacity Pressure Fryers 2-12

Table 2-3 Projected Energy Consumption for Gas Fryers 2-17

Table 2-4 Projected Energy Consumption for Electric Fryers 2-18

Table 3-1 Energy Efficiency for 910 mm (36 in) Griddles 3-12

Table 3-2 Projected Energy Consumption for Gas Griddles 3-17

Table 3-3 Projected Energy Consumption for Electric Griddles 3-17 Table 4-1 Typical Broiler Grid Dimensions 4-5 Table 4-2 Broiler Cooking Energy Efficiency 4-9 Table 4-3 Projected Energy Consumption for Gas Broilers 4-10

Table 4-4 Projected Energy Consumption for Electric. Broilers 4-11

Technology Review of Commercial Foodservice Equipment Volume II, Page v Table 5-1 Range Top Energy Efficiency 5-10

Table 5-3 Projected Energy Consumption for Gas Ranges 5-11 Table 5-4 Projected Energy Consumption for Electric Broilers 5-11

Table 6-1 Summary of Chinese Range Types 6-5

Table 6-2 Chinese Range Energy Efficiency 6-6

Table 6-3 Projected Energy Consumption for Gas Ranges 6-6

Table 7-1 Oven Energy Efficiency 7-15 Table 7-2 Projected Energy Consumption for Gas Ranges 7-18 Table 7-3 Projected Energy Consumption for Electric Broilers 7-19 Table 8-1 Maximum Input Rate Preheat and Idle energy rate for compartment steamers 8-5 Table 8-2 Cooking Energy Efficiency: Summary of Appliance Category (Average for atmospheric and pressureless) 8-7

Table 8-3 Cooking Energy Efficiency, Production Capacity and Water Consumption (ice load test-atmospheric steaming) 8-8

Table 8-4 Projected Energy Consumption for Gas Compartment Steamers 8-9

Table 8-5 Projected Energy Consumption for Electric Compartment Steamers 8-9

Table 9-1 Steam Kettle Performance Comparison Based on Preliminary Data for Three Steam Kettles 9-5

Table 9-2 Benchmark Steam Kettle Cooking Energy Efficiency 9-6

Table 9-3 Projected Energy Consumption for Gas Steam Kettle 9-7

Technology Review of Commercial Foodservice Equipment Volume II, Page \ i Table 9-4 Projected Energy Consumption for

Electric Steam Kettle 9-7

Table 10-1 Braising Pan Cooking Energy Efficiency 10-3

Table 10-2 Projected Energy Consumption for Gas Braising Pan 10-4 Table 10-4 Projected Energy Consumption for Electric Steam Kettle 10-4

Technology Review of Commercial Foodservice Equipment Volume n, Page vii LIST OF FIGURES

Figure 1-1A Typical code requirement 1-13

Figure 1-1B Custom hood (with side panels) requirement 1-13

Figure 1-2B Requirements for electric appliance ventilation 1-15

Figure 1-2B Requirements for gas appliance ventilation 1-15

Figure 1-3 Short-circuit hood with spillage 1-16

Figure 2-1 Standard open deep-fat fryer 2-1

Figure 2-2 A chicken/fish fryer 2-2

Figure 2-3 Donut fryer 2-3

Figure 2-4 Fire tubes in vat of gas fryer 2-4

Figure 2-5 An example of console fryer 2-7

Figure 2-6 Pressure fryer 2-10

Figure 2-7 Gas open deep-fat fryer cooking energy efficiency characteristics 2-11

Figure 2-8 Electric open deep-fat fryer cooking energy efficiency characteristics 2-11

Figure 2-9 Gas pressure fryer cooking energy efficiency characteristics 2-12

Figure 2-10 Electric pressure fryer cooking energy efficiency characteristics 2-13

Figure 2-11 Open deep-fat fryer cooking energy efficiency bandwidths 2-14

Figure 2-12 Pressure fryer cooking energy efficiency bandwidths 2-14

Figure 2-13 Gas open deep-fat fryer energy consumption based on two-mode model 2-15

Technology Review of Commercial Foodservice Equipment Volume II, Page viii Figure 2-14 Electric open deep-fat fryer energy consumption based on two-mode model 2-15

Figure 2-15 Gas pressure fryer energy consumption based on two-mode model 2-16

Figure 2-16 Electric pressure fryer energy

consumption based on two-mode model 2-16

Figure 2-17 Gas "Drop-In" fryer 2-19

Figure 3-1 Typical gas griddle 3-1

Figure 3-2 Griddle as a range component 3-2

Figure 3-3 Gas grooved griddle 3-2

Figure 3-4 Duplex cooker with gas radiants 3-3

Figure 3-5 Lang's heat pipe griddle 3-7

Figure 3-6 Gas 910 mm (36 in) griddle cooking energy efficiency characteristics 3-12 Figure 3-7 Electric 910 mm (36 in) griddle cooking energy efficiency char- 3-13 acteristics

Figure 3-8 910 mm (36 in) griddle cooking energy efficiency bandwidths 3-14

Figure 3-9 Gas 910 mm (36 in) griddle energy consumption based on two-mode model 3-14

Figure 3-10 Gas 910 mm (36 in) griddle energy

consumption based on two-mode model 3-15

Figure 3-11 Griddle energy consumption ranges 3-16

Figure 4-1 Gas underfired charbroiler (# 1) 4-1

Figure 4-2 Gas underfired charbroiler (#2) 4-2

Figure 4-3 Cutaway view of standard underfired gas charbroiler 4-3 Figure 4-4 Diagram of "radiant" style underfired broiler 4-3

Figure 4-5 Overfired upright broiler 4-4

Technology Review of Commercial Foodservice Equipment Volume 11, Page ix Figure 4-6 Backshelf mounted salamander broiler 4-6

Figure 4-7 Cheesemelter-type broiler 4-6 Figure 4-8 Range-mounted salamander 4-7

Figure 4-9 Side view of conveyor broiler 4-7

Figure 4-10 Electric conveyor broiler 4-8

Figure 4-11 Gas combination griddle-broiler with grooved plate . 4-8

Figure 5-1 Six-burner range on oven base 5-1

Figure 6-1 Heavy-Duty gas Chinese wok 6-1

Figure 6-2 East Coast-style range schematic 6-2

Figure 6-3 Traditional Oriental ranges 6-4

Figure 7-1 Stacked, half-size convection ovens 7-1

Figures 8-1 Two-compartment convection steamer on self-contained base 8-1

Figure 8-2 Two-compartment pressure steamer- direct connected 8-2

Figure 8-3 Efficiency of pressurized vs. atmos- pheric steaming in a gas compartment steamer 8-6

Figure 8-4 Effect of loading on cooking energy efficiency in pressureless steaming 8-8

Figure 9-1 Tabletop-mounted, tilting self-con• tained steam kettle 9-1

Figure 10-1 A 150-liter tilting braising pan 10-1

Figure 10-2 A 40-1 iter countertop skillet 10-2

Figure 10-3 Example of insulated braising pan 10-6

Technology Review of Commercial Foodservice Equipment Volume II. Page x 1. INTRODUCTION

1.1 OBJECTIVE The objective of Volume II of the Technology Review of Com• mercial Food service Equipment is to present, on an appliance- by-appliance basis, a comprehensive description and energy performance assessment of commercial food service equipment. The focus is on the potential for improving the energy effi• ciency and overall performance of gas-fired appliances in direct support of the Canadian gas utilities' marketing and energy con• servation initiatives for this end-use sector.

1.1.1 Appliance Categories and Types The categories and types of cooking equipment described in subsequent sections of this report are listed in Table 1-1. Each section has been developed as a stand-alone module, complete with references. It is anticipated that these sections may evolve into training modules for the utility and food service industries.

TABLE 1-1 Appliance Categories and Types

Category Type

FRYER Open Deep Fat Open Kettle Pressure Flat Bottom: - chicken -fish - donut

GRIDDLE Single Sided: -flat - grooved Double Sided

BROILER Underfired (Charbroiler) Overtired: - upright - salamander - cheesemelter Conveyor (chain)

Technology Review of Commercial Foodservice Equipment Volume II, Page l-l ^^nii

TABLE 1-1 Appliance Categories and Types (continued)

Category Type

RANGE Range: - open burner/element - hot top

CHINESE RANGE Traditional Wok North American Wok

OVEN Standard Convection - full size - half size - rack ovens Combination Oven/Steamer Deck Conveyor Rotisserie - rotisserie oven - rotisserie broiler

STEAMER Compartment Pressureless ! 1 - convection - boiler Compartment Pressurized

STEAM KETTLE Steam Kettle

BRAISING PAN Braising Panmiting Skillet

1.2 BACKGROUND

1.2.1 Energy Performance It is difficult to estimate the energy consumption for specific cooking appliances based on the nameplate energy input rate. Although it is easily understood that a cooking appliance will not draw power or consume gas at its peak input rate, it is not as easy to project the average rate of energy consumption for the various appliances that one might encounter in a restaurant kitchen. The amount of energy consumed by commercial cook• O ing equipment is dependent on the operating time of an appli-

Technology Review of Commercial Foodservice Equipment Volume II, Page 1-2 ance, the cooking surface or cavity temperature (based on a se• lected thermostat set point) and/or heat-input setting (e.g., "high", "medium" or "low" input energy control), the quantity of food being cooked and, for some appliances, the mode of op• eration. The relative dependence of appliance energy consump• tion on each of these variables is a function of equipment type and design, as well as on the usage of an appliance within a specific food service operation. For eight generic appliance types evaluated within the scope of an appliance energy end use monitoring project,111 a large variation in the characteristic en• ergy demand and consumption was documented. This also was reflected by the reported range in the duty cycles (i.e., from 12 to 92%) of appliance burners or elements for each category of equipment. The duty cycle of an appliance is defined as the av• erage rate of energy consumption expressed as a percentage of the rated energy input or the peak rate at which an appliance can use energy. Thermostat vs. Non-Thermostat Control. Whether an appli• ance type incorporates a thermostat can impact significantly on the characteristic energy consumption of that appliance. For ex• ample, a gas broiler consumes energy at a rate that is close to its input rate as thermostat control is not incorporated. Characteris• tically different from the broiler is an appliance such as the fryer which is thermostatically controlled. The average rate of energy consumption required to maintain the frying oil at approxi• mately 177°C (350°F) is 15 to 20% of the rated energy input for fryers. '

1.2.2 Situation Analysis A recent study'21 published by the U.S. Department of Energy titled Characterization of Commercial Building Appliances ef• fectively summarizes the status of cooking technologies and foreshadows the importance of R&D initiatives designed to im• prove the performance of commercial cooking equipment: AH commercial food service equipment is represented in both gas-fired and electric models. The efficiency of commercially available gas-fired cooking equipment varies significantly de• pending on the specific manufacturer and model. There are no mandated minimum efficiency standards in this industry, and uniform test procedures for measuring actual cooking efficien• cies are in the process of being developed (ref PG&E Food Service Technology Center). The largest impact on the future efficiency of the installed base of cooking equipment will de• pend more on factors that influence the purchase decision cri• teria for the equipment than on technology developments. Quite

Technology Review of Commercial Foodservice Equipment Volume II, Page 1 -3 simply, the installed base of commercial gas-fired cooking equipment efficiencies could be significantly increased if cus• tomers purchased more efficient models. However, the cost premium associated with the high efficiency cooking equipment does not always justify the resultant savings. As a result, projecting future efficiencies, we need to consider customer trends and driving forces behind the more energy ef• ficient system. Often times, the higher efficiency systems also provide better cooking performance which is extremely impor• tant to the fast food chains. Electric powered cooking equip• ment has not changed in efficiency as dramatically as gas-fired models. In addition to the low-first-cost economic pressure on the food service operator to purchase efficient equipment, the general lack of objective performance data has slowed the development of energy efficient equipment. If the buyer is not exposed to ac• curate bench-mark performance data, there is less incentive on the part of the manufacturers to improve equipment perform• ance. As identified by the DOE study, the absence of gov• ernment legislation specifying minimum efficiencies for cook• ing equipment is another factor in the "slow-development" equation for improving the energy performance of cooking equipment.

Technology Review of Commercial Foodservice Equipment Volume II, Page 1-4 1.3 STANDARD TEST METHOD DEVELOPMENT In 1987, with co-funding by the Electric Power Research Insti• tute (EPRI), the Gas Research Institute (GRI), and the National Restaurant Association, the Pacific Gas and Electric Company (PG&E) undertook the development of uniform testing proce• dures to measure the energy efficiency and evaluate the overall performance of gas and electric cooking equipment within the scope of its Food Service Technology Center in San Ramon, California. When the PG&E research team completes a uniform testing procedure for a particular appliance category, [3"7] the document is submitted to the ASTM F 26.06 Food Service Equipment Subcommittee on Productivity and Energy Protocols. The test• ing procedure is then reviewed by this group of industry pro• fessionals before it is balloted by the main F 26 Food Service Equipment Committee. Once approved by the main committee, the testing procedure is submitted for Society ballot and pub• lished as an official ASTM Standard Test Method.

1.3.1 ASTM Test Methods Benefit Food Service Industry The application of an ASTM standard test method to cooking equipment provides end-users with performance parameters that can be used to compare the energy efficiency, production capacity, cooking surface/cavity uniformity, etc. of one piece of equipment with another. A unique aspect of the test methods is that the pro• ductivity (i.e., production capacity) and energy efficiency are determined from the same test using standardized food product under tightly controlled conditions. From the perspective of energy efficiency, it is important to com• pare a gas appliance with other gas appliances and an electric appliance with other electric equipment. Since the energy efficiency of a gas appliance is inherently lower than it is for its electric counterpart, a purchaser must establish different minimums for gas and electric equipment. For example, an end-user might choose to specify a minimum full-load cooking energy efficiency of 50% for gas fryers and while requiring a minimum of 80% for electric fryers. The specification of the production capacity (i.e., weight of food cooked per hour) should be the same for both gas and electric appliances, as the "work" that a cooking appliance is required to do for the end-user is the same. Similarly, performance parameters such as cooking surface/cavity temperature uniformity apply equally to gas and electric appliances.

Technology Review of Commercial Foodservice Equipment Volume II, Page 1-5 The ASTM standard test methods for cooking appliances pro• vide new tools for food service equipment manufacturers to validate their research and development efforts and for food service equipment purchasers to define minimum performance requirements within their equipment specifications.

1.3.2 Status of ASTM Test Methods Standard test methods developed by PG&E and ratified by the ASTM F26 Committee on Food Service Equipment include: 1. ASTM Standard Test Method for the Performance of Steam Cookers, Designation: F 1484-93 2. ASTM Standard Test Method for the Performance of Con• vection Ovens, Designation: F 1496-93 3. ASTM Standard Test Method for the Performance of Range Tops, Designation: F 1521-94 4. ASTM Standard Test Method for the Performance of Double- Sided Griddles, Designation: F 1605-95 5. ASTM Standard Test Method for the Performance of Grid• dles, Designation: F 1275-95 6. ASTM Standard Test Method for the Performance of Open Deep-Fat Fryers, Designation: F 1361-95 7. ASTM Standard Test Method for the Performance of Combination Ovens, Designation: F 1639-96 Under active development or in the ASTM balloting process are test methods for underfired broilers, door-type dishwashers, steam kettles, braising pans, pasta cookers, conveyor ovens, ro- tisseries, deck ovens, and pressure fryers. On the horizon are test methods for overfired broilers, conveyor dishwashers, flat- bottom fryers, Chinese ranges, roll-in ovens and steam tables.

1.4 APPLIANCE ENERGY EFFICIENCY Cooking appliance energy efficiency is a measure of how much of the energy that an appliance consumes is converted into useful heat. A more refined definition, cooking-energy efficiency reflects the amount of energy that is actually delivered to the food product during the cooking process. For example, a simple and precise way to quantify the energy efficiency of a griddle or fryer is to conduct a water-boil test. For a griddle, temporary side walls are attached to the cooking surface that is then covered with several inches of water. In the case of a fryer, the fry pot is filled with water instead of frying medium. The appliance is then placed on a large balance scale and connected to

Technology Review of Commercial Foodservice Equipment Volume II, Page 1-6 the appropriate energy source. Once a stable boil has been attained. both the weight of water being boiled off and the energy consumed by the appliance are recorded. The energy efficiency of the griddle D or fryer is then calculated by dividing the energy absorbed by the water that was boiled off (based on the heat of vapourisation = 970 Btu/lb) by the energy consumed by the appliance during the water-boil test. But not many food service operators boil water on their griddle or in their fryer. As one fast food operator stated, "I want to know how energy efficient a griddle is when it is being used to cook ham• burger patties—not water!" Hamburger patties and French fries were much more "palatable" as standard test foods for the ASTM griddle and fryer procedures. The ASTM test methods for measuring cooking appliance energy efficiency have been based on the following definition and general equations: cooking energy efficiency—quantity of energy imparted to the speci• fied food product, expressed as a percentage of energy consumed by the appliance during the cooking event; t]cook

r\ 2^- x 100 'appliance where: *\cook see cooking energy efficiency ^appliance energy into the appliance &food see energy to food

= ECPnc +Etha w + E evap- where; £ quantity of heat added to food product, which causes their temperature to increase from the starting tempera• ture to the average bulk temperature of a "done" food product flri)(Cp)(Tf-T,) where: W, initial weight of food product, lb (kg) cP specific heat of food product, Btu/lb, °F (kJ/kg, °C) Tf final cooked temperature of food product, °F (°C) T; initial internal temperature of food product, °F (°C)

'thaw latent heat (of fusion) added to the food product, which causes the moisture (in the form of ice) contained in the food product to melt when the temperature of the food product reaches 32°F (0°C)

where: Wiw = initial weight of water in the food product, lb (kg), Hf = heat of fusion, Btu/lb (kJ/kg), and

Technology Review of Commercial Foodservice Equipment Volume H, Page 1-7 = 144 Btu/lb (336 kJ/kg) at 32°F (0°C). Eevap = latent heat (of vapourization) added to the food product, which causes some of the moisture contained in the food product to evaporate. = Wloss x Hy where: Wioss = weight loss of water during cooking, lb (kg), Hv = heat of vapourization, Btu/lb (kJ/kg), = 970 Btu/lb (2256 kJ/kg) at 212°F (100°C)

Table 1 -2 lists the benchmark cooking-energy efficiencies that were compiled within the scope of this study. These cooking efficiencies are based on both measured and estimated performance of a cook• ing appliance under discrete full-load tests (e.g., oven) or full-load barreling tests (e.g., fryer) as described by the ASTM Test Methods. The source of these estimates are discussed in each appliance section. Of significance to this study's objective, is the relatively low efficiencies (e.g., 20 - 50%) for standard gas appliances. One would conclude that there is significant potential for raising the base efficiency of gas-fired cooking equipment. It is important to recognize that cooking appliances are more efficient when they are cooking food at peak capacity (i.e., fully loaded). In the real world, appliances typically are not used to capacity. Thus, part load performance is important and has been in• corporated within the ASTM testing procedures. Similar to other energy consuming equipment such as heat pumps or gas boilers, the energy efficiency is reduced under part-load operation. The amount of time that an appliance is left idling in a "ready-to-cook" mode also adds to the denominator of the real-kitchen energy efficiency equation. Neither the part-load performance nor the in-kitchen utilization are reflected by the efficiencies in Table 1-2. Alterna• tively stated, the real-world energy utilization efficiencies of gas cooking equipment is very low (e.g., 5 -10%).

1.5 GAS/ELECTRIC CONSUMPTION RATIOS The ratio of energy consumption between a gas appliance and its electric counterpart is an energy performance parameter often used by the industry. Ratios of energy consumed by a gas appli• ance to its electric counterpart were reported by the Minnesota Study1' and subsequently reported by the American Gas Asso• ciation. ' However, these ratios were based on full-load cooking tests applied to one gas and one electric appliance in each equipment category. Table 1-3 presents the energy ratios pub• lished by AGA.

Technology Review of Commercial Foodservice Equipment Volume II, Page 1-8 TABLE 1-2 Benchmark Cooking-Energy Efficiency" Summary

Standard High Electric o Gas Efficiency Gas

FRYER: Open Deep Fat 25-50 50-60 75-85 Pressure/Kettle 25-35 35-50 65-85 Flat Bottom 25-35 35-50 65-85

GRIDDLE 25-35 40-50 65-75

BROILER 15-30 35-65

RANGE TOP 25-30 45-60 65-85

WOK 15-30 50-70

OVEN: Std./Conv./Comb. 30-40 40-50 50-80 Deck 20-30 40-60 Conveyor 10-20 20-40 Rotisserie 20-30 50-60

COMPARTMENT STEAMER 30 - 40 60-80

STEAM KETTLE 40 - 60 80-95

BRAISING PAN 30 - 55 80-95

a Energ\ efficiencies are for full-load cooking scenarios

Although this data provided an excellent tool for comparing gas and electric appliance energy consumption (and cost), the fact that the ratios were based on full-load testing generated an op• timistic comparison for some of the equipment categories. This is because the efficiency of a gas appliance under part-load op• eration may be less than it is under full-load conditions. The AGA ratios do not consider the fact that an appliance in an actual food service operation may spend much of its time idling or under light-duty operation. The ratio of energy consumption

Technology Review of Commercial Foodservice Equipment Volume H, Page 1-9 TABLE 1-3 AGA Published Gas/Electric Energy Ratios1®

Appliance Energy Ratio Gas to Electric Broiler 1.4 Braising pan 1.8 Fryer, standard 2.0 Fryer, pressure 2.3 Griddle, flat 1.4 Griddle, grooved 1.4 Oven, convection 1.5 Oven, deck 2.2 Range, hot top 2.0 Range, open burner 2.0 Steam kettle 1.7 Steamer, atmospheric 1.5 Steamer, pressure 2.1 between every gas and electric appliance combination in the same category is not a precise number—it can vary depending on the specific model of gas and electric appliance being com• pared and on the usage of the appliance in the commercial kitchen. It is also a function of the technology incorporated in either the gas or electric unit (e.g., infrared burners). For exam• ple, if one compares the least efficient electric griddle with the most efficient gas griddle, the energy consumption ratio will be lower (e.g., ratio = 1.5) than if one compares the most efficient electric griddle with the least efficient gas griddle (e.g., ratio = 2.5). However, the average ratio for all electric griddles com• pared to all gas griddles under typical real-world conditions may be somewhere in between (e.g., ratio = 2.0). Estimates of real-world energy consumption ratios for gas and electric appliances are presented in Table 1-4 based on the aver• age rate of energy consumption reported in the respective appli• ance sections. These average energy consumption rates were estimated using either an energy consumption model or typical appliance duty cycles estimated from available end-use monitor• ing data.

Technology Review of Commercial Foodservice Equipment Volume II, Page 1-10 TABLE 1-4 Gas/Electric Energy Consumption Ratios

Average Energy Energy o Consumption Ratio Gas Eleca Gas/Elec

DEEP-FAT FRYER 20 10 2.0

GRIDDLE 23 10 2.3

UNDERFIRED BROILER 84 27 3.1

RANGE 48 17 2.8

CONVECTION OVEN 25 17 1.5

COMPARTMENT STEAMER 32 17 1.9

STEAM KETTLE 50 27 1.9

BRAISING PAN 40 24 1.7

"Conversion Factor = 3.413 (kBtu/kWh)

; 1.6 VENTILATION REQUIREMENTS

1.6.1 Background The need to exhaust heat and vapours associated with the op• eration of commercial cooking equipment directly impacts on the energy demand and consumption of food service facilities. It has been demonstrated that the HVAC load represents approxi• mately 30% of the total energy consumed in a restaurant. ] It has been further estimated1! ' that the kitchen ventilation system can account for up to 75% of the HVAC load and, as such, rep• resents the largest single-system, energy consumer in food service operations. Historically, commercial kitchen exhaust ventilation systems have been designed, installed and operated with little consid• eration for energy management and conservation. Under• standably, this can be attributed to the relatively low cost of en• ergy in the past and the fact that designers have been concerned with the capability of the systems to capture, contain and re• move cooking contaminants without consideration for the op• erating costs. Not that kitchen exhaust systems designed accord• ing to code are necessarily inadequate from the perspective of removing grease, odors and heat from the commercial kitchen.

Technology Review of Commercial Foodservice Equipment Volume II, Page 1-11 In fact, the general concern with respect to energy conservation is the large "safety factor" that has been built into the codes and design guidelines (Figure 1-1 A). For example, 0.51 m/s to 0.76 m/s (100 to 150 fpm) face veloc• ity is usually required, but levels as low as 0.25 m/s to 0.38 m/s (50 to 75 fpm) have been shown to be satisfactory[,2] An ex• perimental study1'31 published by ASHRAE reported that for wall and island canopies, only 40 to 50% of the normal design flow was required to provide satisfactory capture of smoke gen• erated at any location on or beside the cooking surfaces (Figure 1-1B). These studies are consistent with research and develop• ment conducted by the McDonald's Corporation.[14] In general, their laboratory-based hood design and sizing procedures have allowed them to install exhaust systems that operate at an ex• haust ventilation rate that is significantly less (e.g., 50%) than that specified by U.S. codes.

1.6.2 Influence of U.S. Codes Design guidelines for kitchen ventilation systems in Canada have been influenced strongly by codes in the U.S. Codes such as the Uniform Mechanical Code, Uniform Building Code, and up to 1973, the National Fire Protection Association (NFPA Standard No. 96) which list the required exhaust air quantities according to the type, placement and face area of the exhaust hood. Unfortunately, these design criteria were not based on actual performance evaluation of exhaust systems operating over different pieces (or groups) of operating cooking equip• ment.

A study conducted by the National Conference of States on Building Codes and Standards (NCSBCS) under contract with the Electric Power Research Institute documented the lack of uniformity in the way kitchen exhaust system design criteria and codes are applied across the country.15) This study, titled an Assessment of Building Codes, Standards and Regulationslm- pacting Commercial Kitchen Design, revealed:

"...a lack of correlation between effluent characteristics and exhaust requirements. Codes generally treat all cooking proc• esses identically, although different processes may produce such varying effluents as heat, grease, vapour, odors, steam, or smoke. In addition, state codes frequently differ in how they

Technology Review of Commercial Foodservice Equipment Volume II, Page 1-12 Exahust ven! Nation rate based on 10C cfm per square foot o' hood area

Cods Example 4 ft x 4ft x 13Dcfmflt2 = ISSDcfm

FIGURE 1-1A Typical Cods Requirement

Exhaust ventilation rate based on labora• tory performance of custom hood design.

Example: 4 ft. x 200 cfm per linear ft. = 800 cfm

FIGURE 1-1B Custom Hood (with Side Panels) Requirement

Technology Review of Commercial Foodservice Equipment Volume II, Page 1-13 regulate cooking processes that produce the same effluents. In general, many code provisions have no clear technical docu• mentation, and available technical studies indicate that code ventilation requirements often substantially exceed actual needs."

1.6.3 Gas vs. Electric Although it is generally acknowledged that a higher exhaust ventilation rate may be required for most gas appliances, the actual magnitude (expressed as a fraction of the exhaust air rate) of the combustion products has not been documented (Fig. 1.2 A and 1.2B). Furthermore, there is no documentation of the 20% advantage in the design ventilation rate permitted by the Uni• form Mechanical Code for an all-electric appliance line.' '*

1.6.4 Short-Circuit Hoods Another controversial issue relates to the performance of what are referred to as "short-circuit" exhaust hoods. Alternatively referred to as "compensating," "no-heat," or "cheater" exhaust hoods, such systems were developed in an attempt to reduce the amount of conditioned makeup air required by an exhaust sys• tem designed to code. By introducing a portion of the required makeup air in an untempered condition directly into the exhaust hood itself, the net amount of conditioned air exhausted from the kitchen is reduced. Thus, the total exhaust capacity of the system will be able to meet conservative design requirements while the actual quantity of makeup air that needs to be heated or cooled is minimized. But if less "net" exhaust air is adequate, why not simply design the exhaust system to ventilate the cooking equipment at a reduced rate in the first place. A good idea, but the short-circuit hood continues to propagate within the industry. And in actual installations, the amount of short- circuited air often reduces the net ventilation to the point where spillage of cooking effluent occurs (Figure 1-3), compromising the kitchen environment.

1.6.5 ASHRAE Initiatives Technical issues and concerns related to kitchen ventilation have been discussed at ASHRAE forums, seminars, symposia and technical sessions for a number of years. In an effort to fo• cus ASHRAE's effort in this area, and to meet a perceived need of its membership, an ASHRAE task group on kitchen ventila• tion has been established (TG 5.KV). The mission of this

Technolog\ Review of Commercial Foodservice Equipment Volume II. Page 1-14 Thermal Updraft and GooKing Effluenl It is generally acknowledged tha'. there are different ventilation requirements for different apphances based on the quantity of heal and vapors producted by (he cooking process

Re place­pen'. Air

FIGURE 1­2A Requirements for Electric Appliance Ventilation

Thermal Updraft Cooking Effluen". ar,d Products o'­ Combustion

'/::■. Th» impact of combustion products oi the ventilation requirements of cooking appli­ ances is not weM established.

Replacement and Comcustion Air

FIGURE 1­2B Requirements for Gas Appliance Ventilation

Technology Review of Commercial Foodservice Equipment Volume II, Page 1­15 FIGURE 1-3 Short-Circuit Hood with Spillage

committee on kitchen ventilation is to address the needs of ASHRAE membership with respect to the energy efficient con• trol, capture and effective removal of airborne contaminants and heat resulting from the cooking processes. The technical scope includes the introduction of supply and makeup air as it influ• • ences the contaminant control process, and the thermal envi• ronment in the cooking space. Implementation of supporting research and the development of an ASHRAE standard on kitchen ventilation is a primary goal of the committee, as was the publication of a new Handbook Chapter on Kitchen Venti- lation.tl6] The focus of the proposed ASHRAE standard will be towards optimizing the design and operation of the commercial kitchen ventilating systems with respect to system performance (e.g., capture and containment) with a major emphasis on energy con• servation and pollution control (indoor and outdoor). This stan• dard is the responsibility of a new Standard Project Committee, SPC154P. Ultimately, the goal of the ASHRAE standard is to impact standardization of the mechanical codes across North America.

1.6.6 Exhaust Ventilation Rates Exhaust flow rate requirements1161 to capture, contain and re• move the effluent vary considerably depending on the hood style, the amount of overhang, the distance from the hood to the

Technology Review of Commercial Foodservice Equipment Volume II, Page 1-16 cooking appliances, the presence and size of end panels, and the cooking equipment and food product involved. The hot cooking surfaces and product vapours create thermal air currents that are "received" or captured by the hood and then exhausted. The velocity of these currents depends largely upon the surface tem• perature and tends to vary from 0.076 m/s (15 fpm) over steam equipment to 0.76 m/s (150 fpm) over charcoal broilers. The actual required flow rate is determined by these thermal cur• rents, a safety allowance to account for crossdrafts and flare- ups, and a safety factor for the style of hood and configuration of makeup air system. The approach ASHRAE takes is to categorize cooking equip• ment into four groups. While published equipment classification varies, and accurate documentation does not exist, the following reflects the consensus opinion of the membership of ASHRAE TG 5.KV and is listed in Chapter 28 of the 1995 ASHRAE Applications Handbook'161 as: 1. Light duty, such as ovens, steamers, and small kettles (up to 204°C (400°F)) 2. Medium duty, such as large kettles, ranges, griddles, and fryers (up to 204°C (400°F)) 3. Heavy duty, such as upright broilers, charbroilers, and woks(upto316°C(600°F)) 4. Extra heavy duty, such as solid fuel-burning equipment (up to 370°C ( 700°F)) Acknowledging that variance in product or volume could shift an appliance into another category, the exhaust flow rate re• quirement is based on the classification of equipment under the hood. If there is more than one category, the flow rate is based on the heaviest duty group, unless the hood design permits dif• ferent volumes over different sections of the hood. Listed hoods are allowed to operate at their listed exhaust flow rates by exceptions in the model U.S. codes. Most manufactur• ers verify their listed flow rates by conducting tests per UL Standard 710.[l7] Minimum exhaust flow rates for listed hoods serving single categories of equipment vary from manufacturer to manufacturer, but are typically as shown in Table 1-5.' Actual exhaust flow rates for hoods with internal "short circuit" makeup air are typically higher than those in Table 1-5, al• though the net exhaust (i.e., total exhaust less short-circuit makeup air) may be similar.

Technology Review of Commercial Foodservice Equipment Volume II, Page 1-17 TABLE 1-5 Typical Minimum Exhaust flow Rates for Listed Hoods by Cooking Equipment Type[16}

Type of Hood Light Medium Heavy Extra Duty Duty Duty Heavy (cfm) (cfm) (cfm) Duty

Wall-Mounted 150-200 200 - 300 200-400 350 + Canopy

Single Island 250 - 300 300-400 300-600 550 +

Double Island 150-200 200 - 300 300-600 500 + (per side)

Eyebrow 150-250 150-250 — —

Backshelf 100-200 200 -300 300 - 400 not recom.

1.6.7 Radiant Heat Gain to Kitchen Heat gain from commercial cooking appliances may have a major impact on the air conditioning load and thermal comfort of a commercial kitchen. To estimate heat gain for building de• sign of a commercial kitchen, engineers currently use Table 8 in Chapter 26 of the ASHRAE Handbook of Fundamentals.1'81 However, there is significant controversy within the industry as to the accuracy of the published radiant factors and derived heat gain values for the different appliance categories, particularly as it relates to gas versus electric equipment. '2 ] In technical re• sponse, the gas and electric industries have worked in concert to develop a standard test method that is being applied to update appliance heat gain data for the ASHRAE Handbook.[2],22]

1.6.8 Kitchen Ventilation Research/Utility Market Needs The development of a comprehensive design manual for com• mercial kitchen exhaust ventilation systems that would com• plement the new ASHRAE Handbook chapter but be targeted specifically towards the Canadian hospitality industry is rec• ommended. Gas industry R&D efforts should focus on optimizing appli• ance/hood systems that will reduce both ventilation require• ments and kitchen heat gain. Such initiatives will serve the in• terests of both manufacturers and end-users of commercial cooking appliances and exhaust systems.

Technology Review of Commercial Foodservice Equipment Volume II. Page 1-18 1.7 EMISSIONS FROM COMMERCIAL COOKING

1.7.1 Clean Air Act 3 The Clean Air Act (CAA), first enacted by Congress in 1967, oversees and regulates the impact of environmental stresses im• posed by industries in the U.S. Most importantly, it facilitates the establishment and implementation of air pollution standards at federal and state levels. The Environmental Protection Agency (EPA) established the national ambient air quality stan• dards (NAAQS) to define the specific levels of air quality that must be achieved for health reasons.

1.7.2 Air Quality Management Districts The enforcement of the Clean Air Act in the U.S. has been dele• gated to local government regulatory agencies called Air Qual• ity management Districts (AQMD's). In areas of non• compliance with the CAA, the AQMD's were first created by state legislation. These local agencies were then mandated to develop strategies to control polluting sources and provide nec• essary resources to enforce the requirements of the CAA in daily industry operation. The South Coast Air Quality Management District (SCAQMD) has jurisdiction over the four-county Los Angeles basin that is one of the most severe non-attainment areas in the United States for PM10 (particulate matter less than 10 microns in diameter) and ozone. The combination of severe air pollution and earlier EPA concerns over charbroiling operations gave rise to the first local regulation of restaurant emissions through Rule 219—a regulation requiring permitting of underfired broilers by SCAQMD. This regulation regulated underfired broilers for smoke and odor. This legislation, although still in effect, will be displaced by the more comprehensive Rule 1138 when it is en• acted.

1.7.3 Restaurant Emissions The argument is not that commercial cooking processes con• tribute to urban air pollution . What is being debated is just how much of the pollution is actually coming from restaurants and, furthermore, from which restaurants is it coming. From fast- food to full-service, from institutional to mom-and-pop opera• tions, the unknown exceed the known when it comes to restau• rant emissions.

Technology Review of Commercial Foodservice Equipment Volume II, Page 1-19 The variation in the types of restaurants, the diversity of menus and appliances, the lack of consensus-based methods for meas• uring emissions from cooking processes challenge the South ~y Coast Air Quality Management District (SCAQMD) as they try to implement legislation that will reduce the contribution to air pollution from the food service industry in the Los Angeles ba• sin. And we can be assured that urban centers with increasing air pollution in both the U.S. and Canada are closely watching California. A 1994 research report' J takes a macro look at the picture, con• cluding that meat cooking contributes to 17% of the total carbo• naceous aerosol emissions in the Los Angeles basin. It was also reported1231 that people in the United States consumed about 40% of their meat (including beef, port, lamb, poultry and sea• food) in restaurants. If this ratio held true for California, a gross calculation would imply that 17% x 0.4 = 7% of the Los Ange• les pollution was due to cooking meat in restaurants. 1.7.3.1 Rule 1138 as First Proposed in 1994. SCAQMD's pro• posed rule 1138, known as the Restaurant Rule, was developed to reduce concentrations of both particulate matter (PM) and reactive organic gases (ROGs) being emitted from commercial cooking processes. Note that ROGs are often referred to as volatile organic compounds (VOCs). Two years from the adoption date of the rule for new restaurants, and three years for existing res• taurants, emission levels may not exceed: • 0.45 kg/day (1.00 lb) of PM emissions per restaurant, averaged over a calendar month • 1.0 kg/day (2.25 lb) of ROG emissions averaged over a calendar month Seven years from adoption, emission levels in all restaurants may not exceed: • 0.18 kg/day (0.40 lb) of PM emissions per restaurant, averaged over a calendar month • 0.23 kg/day (0.50 lb) of ROG emissions av• eraged over a calendar month The basis for the above limits is SCAQMD's assertion that 1 lb of particulate matter (PM) and 1 lb of reactive organic gases (ROGs) are produced for every 125 lb (57 kg) of meat broiled. This is expressed as an emission factor of 0.008 lb of emission per lb of raw meat cooked (i.e., 1 * 125 = 0.008 lb/lb). Thus if

Technology Review of Commercial Foodservice Equipment Volume II, Page 1-20 a restaurant broils more than 125 lb of meat, the quantity of particulate (PM) would exceed 1 lb and they would be in viola• tion of the rule. 1.7.3.2 Rule Compliance. Originally, two strategies were pro• posed for verifying a restaurant's compliance with the rule. They were: 1) Restaurant-by-restaurant source testing (i.e., on-site emissions measurements) 2) Listing of emission factors for various types and sizes of cooking appliances, hoods and control de• vices determined through standardized laboratory testing—otherwise referred to by SCAQMD as "The Book." Because of the large variation in data from using the PM and ROG protocols in the field (i.e., source testing), SCAQMD has focused on the second strategy for rule compliance. This work is being undertaken by the University of California, Riverside, College of Engineering - Center for Environmental Research and Technology (CE-CERT). 1.7.3.3 Emission Measurement. SCAQMD currently recog• nizes a modified EPA test method designated Method 5.1, De• termination of Particulate Matter Emissions from Stationary Sources Using a Wet Impingement Train and a modified EPA test method designated Method 25.1, Determination of Total Gaseous Non-Methane Organic Emissions as Carbon. Grease vapour and aerosols—the constant in restaurant emis• sions—represent a big part of the challenge as the standard in• dustry test methods are applied to the restaurant exhaust stream. Of the two protocols, Method 5.1 for PM has demonstrated the best repeatability when emission measurements from the same cooking process are replicated. Method 25.1 continues to chal• lenge researchers and source testing experts as they apply this test method to cooking effluent. 1.7.3.4 Characteristics of Cooking Effluent. The composition of the effluent from different food products being cooked on different types of equipment varies significantly. Furthermore, the composition of a specific food product itself may impact the composition of emission (e.g., 20% versus 30% fat content hamburger patties). A primary component (particularly the visible part) may include fly ash and smoke from the combus• tion of grease and solid fuels. But grease, existing as both an ultra-fine aerosol and a vapour, is a major component of the emission plume from a meat cooking process.

Technology Review of Commercial Foodservice Equipment Volume II, Page 1 -21 1.7.3.5 Best Available Control Technology (BACT). Control strategies that are considered candidates for reducing restaurant ) emissions include: • Electrostatic precipitators (ESPs) • High efficiency filtration/adsorption • Catalytic converters • Scrubbers • Afterburners • Any type of filtration equipment that reduces emissions • Change in the cooking process/equipment. The pollutant-removal efficiency of such devices and strategies, when applied to restaurant exhaust, is not well documented. At this time, no consensus-based standard test methods exist for rating the performance of grease extraction or emission control equipment. Depending on the design and size of the kitchen exhaust ventila• tion system, installed cost for the emission control package may range from $10,000 to $100,000, with little known about main• tenance or durability. The more one pays for the equipment, the better one can expect it to work. But the cost of installing and maintaining an "industrial strength" air cleaning system that will do the job for the next 20 years may be much higher than the restaurant operator is prepared to spend. The food service con• sultant or engineer faced with specifying such equipment has his/her work cut out when they take on the design of a new fa• cility where the "authority having jurisdiction" is demanding emission control. 1.7.3.6 Prognosis. By the end of 1996, the Restaurant Rule is expected to become a reality in Southern California. If the Res• taurant Rule is successfully implemented in the Los Angeles, AQMD's in other areas that are in non-compliance with EPA's threshold limits for emissions may adopt similar legislation. Higher-volume restaurants, particularly those with underfired broilers, may be required to install emission control equipment. On the longer term, exhaust ventilation systems with integrated emission control may become standard equipment for restau• rants doing business in urban areas in the U.S. and Canada. The reality is that ventilating and controlling emissions from cook• ing equipment will become an integral cost of doing business in what is becoming a much more technically sophisticated indus• try.

Technology Review of Commercial Foodservice Equipment Volume II, Page 1-22 1.8 CONCLUSIONS Appliance energy performance data, which can help a utility implement successful conservation programs, also can effec• tively serve a utility's interests as it pursues market retention or expansion in the restaurant sector. The better one understands "how" a cooking appliance or process uses energy, the better one's position with respect to marketing the "use" of that appli• ance or process. Overall recommendations that CGRI, with support from Cana• dian utilities and Natural Resources Canada, should consider within the scope of energy efficiency programs for the hospital• ity sector include: 1. Establishing a commercial appliance testing program that can be used to further bench mark energy performance in direct support of R&D projects for commercial cooking equipment. 2. Using benchmark performance data as justification, develop• ing an industry strategy that will influence the purchase- decision criteria so that customers will specify more energy efficient equipment. 3. Developing and sponsoring training courses and workshops for the Canadian food service and utility industries based on CGRI's appliance technology review. 4. Initiating research and development projects that will deliver the greatest return for R&D dollars invested (i.e., that achieve the largest efficiency gain for the largest percentage of equipment installed in Canadian food service facilities). The R&D focus needs to be on improving part-load performance of gas cooking equipment and reducing the cost premium as• sociated with producing more efficient equipment. 5. Collaborating with the U.S. and European utilities and re• search groups (such as Gaz de France) on appliance R&D initiatives. 6. Developing an appliance efficiency directory based on data acquired through testing in accordance with the ASTM stan• dard test methods for evaluating the performance of com• mercial cooking equipment. Initially such a directory would rely extensively on the efficiencies reported by PG&E and cover only a fraction of the cooking equipment on the mar• ket. However, such an initiative would increase awareness in the industry, hence stimulate manufacturers to have their equipment tested in accordance with the ASTM test methods in other U.S. and Canadian laboratories. A natural extension would be a voluntary labeling program that would report the

Technology Review of Commercial Foodservice Equipment Volume 31, Page 1 -23 efficiency for a given appliance in a format similar to the En• ergy Guide sticker used for residential appliances.

1.9 REFERENCES 1. PG&E, 1990. Cooking Appliance Performance Report - PG&E Production-Test Kitchen. PG&E Research and De• velopment Report No. 008.1-90.8, May. This reference en• compasses appliance performance reports subsequently published by PG&E (individual reports are cited in each appliance section of this report). 2. Arthur D. Little, Inc., 1993. Characterization of Commer• cial Building Appliances. Prepared for U.S. Department of Energy, ADL Reference No. 42520, June. 3. Kaufman, D.A., Fisher, D.R., Nickel, J. and Saltmarch M., 1989. Development and Application of a Uniform Testing Procedure for Griddles. PG&E Research and Develop• ment Report 008.1-89.2, March. 4. Conner, M. M., Young, R., Fisher, D.R. and Nickel, J., 1991. Development and Application of a Uniform Testing Procedure for Fryers. PG&E Research and Development Report No. 008.1.89.2, November. 5. Blessent, J., 1994. Development and Application of a Uni• form Testing Procedure for Convection Ovens. PG&E Re• search and Development Report No. 008.1-94.12, May. 6. Young, R., 1994. Development and Application of a Uni• form Testing Procedure for Range Tops. PG&E Research and Development Report, Publication pending. 7. Selden, M., 1994. Development and Application of a Uni• form Testing Procedure for Steam Cookers. PG&E Re• search and Development Report, Publication pending. 8. Snyder, O.P., Thompson, D.R. and Norwig, J.F., 1983. Comparative Gas/Electric Food Service Equipment Energy Consumption Ratio Study. University of Minnesota, March. 9. American Gas Association, 1989. Commercial Kitchens. 10. Claar, C.N., Mazzucchi, R.P., Heidell, J.A., "The Project on Restaurant Energy Performance (PREP) - End-Use Moni• toring and Analysis", Prepared for the Office of Building Energy Research and Development, DOE, May 1985. 11. Fisher, D.R., Increasing Profits by Optimizing and Con• trolling Kitchen Exhaust Ventilation, a seminar program developed for Energy Mines, and Resources Canada, 1986.

Technolog> Review of Commercial Foodservice Equipment Volume II, Page 1-24 12. Giammer, R.D., Locklin, D.W., Talbert, S.G., Preliminary Study of Ventilation Requirements for Commercial Kitch• ens, ASHRAE Journal, 1971. 13. Talbert, S.G., Flanigan, L.B., Fibling, J.A., An Experimen• tal Study of Ventilation Requirements of Commercial Electric Kitchens, ASHRAE Transactions, 1973. 14. Soling, S.P., and Knapp, J., Laboratory Design of Energy Efficient Exhaust Hoods, ASHRAE Transactions, 1985. 15. The Electric Power Research Institute," Assessment of Building Codes, Standards and Regulations Impacting Commercial Kitchen Design", Research Project Final Re• port, April 1989, prepared for EPR1 by the National Con• ference of States on Building Codes and Standards, Inc. 16. ASHRAE 1995. Handbook of HVAC Applications, Chap• ter 28, Kitchen Ventilation. 17. UL. 1990. Standard for Safety Exhaust Hoods for Com• mercial Cooking Equipment, 4th ed. Standard 710-90. Un• derwriters laboratories, Northbrook, IL. 18. ASHRAE 1993. Handbook of Fundamentals, Chapter 26, Nonresidential Air-Conditioning Cooling and Heating Load. 19. Gordon, E. and Horton, D. If You Can't Stand the heat, Get IT Out of the Kitchen. Cooking for Profit magazine, May 1995. 20. Claar, C, Smith, V. and Krill, W. Too Much Hot Air? The Consultant. Summer 1995. 21. ASTM Standard Test Method for the Performance of Ex• haust Ventilation Systems (Energy Balance Protocol). Pub• lication pending. 1995. 22. Smith, V.A., Swierczyna, R.T., and Claar, C.N. "Application and Enhancement of the Standard Test Method for the Performance of Commercial Kitchen Venti• lation Systems." ASHRAE Transactions 1995, V. 101, Pt. 2. 23. Gordon, E., .Kam, V. and Parvin, F. "Topical Paper: Emis• sions from Commercial Cooking Operations and Methods for Their Determination." American Gas Association Labo• ratories, December 1994. 24. Hildemann, L.M., Kilnedinst, D.B., et al., Cass, G.R. "Sources of Urban Contemporary Carbon Aerosol." Envi• ron. Sci. Technol., Vol 28, NO. 9, 1994.

Technology Review of Commercial Foodservice Equipment Volume II, Page 1-25 25. Raloff, J. "Cholesterol: Up in Smoke; Cooking Meat Dirties the Air More Than Most People Realize." Science News. Vol 140, July 1991.

Technology Review of Commercial Foodservice Equipment Volume II, Page 1-26 2. FRYERS

2.1 INTRODUCTION Fried foods continue to be popular on the Canadian restaurant scene. French friedpotatoe s are still the most common deep fried food, along with onion rings, chicken and sea food. The fryer menu has expanded to include various deep fried snacks such as mushrooms, zucchini, peppers and mozzarella cheese. Equipment manufacturers have responded by designing fryers that operate more efficiently, quickly, safely and conveniently. Fryers are available in a range of configurations. The kettle, or "frypot1', may be split into more than one vat, allowing the operator to prepare different foods without flavor transfer. Some fryers have automatic lifts that lower and raise food baskets. Fryers may have built-in filters that greatly reduce the labor and risk involved in filteringho t oil. Fryers may be countertop units, freestanding floor units, and in batteries of several fryers in one housing. All fryers share a common basic design. Food is cooked in a kettle of 150-190°C (300-375°F) oil. The oil is typically heated by atmospheric or infrared gas burners underneath the kettle or in "fire tubes" that pass through the kettle walls (Figure 2-4). Electric fryers use heating elements immersed in the oil. Energy inputs range from 30-260 kBtu/h for gas fryers and 2-27 kW for electric fryers, Fryers range in capacity from about 7 kg (15 lb) of fat for a small countertop fryer to over 90 kg (200 lb) of fat for the FIGURE 2-1 largest floor model fryersuse d for doughnuts and chicken. Most Standard open deep fat fryer. fryers have a "cold zone" at the bottom of the kettle where bread Photo: Pitco Friatator, Inc. crumbs and other food particles settle. The cold zone is intended to have no convection current and a relatively low temperature, so that food crumbs will not carbonize and create the breakdown products that limit oil life. Fryers are most often compared on the basis of oil capacity and energy input rating. Taken together these two numbers suggest the approximate amount of food a fryer can prepare in a given time, which is one of the most important factors in choosing the proper fryer for a kitchen. The energy cost of operating a fryer can be significant, and different fryers can have quite different patterns of energy use. However, fryer energy use has not been documented until recently, and as a result initial cost generally plays a more important role in appliance purchasing than the energy cost.

Technology Review of Commercial Foodservice Equipment Volume II, Page 2-1 2.2 COOKING PROCESSES Frying is a process of heating and dehydration. The oil in a fryer surrounds and transfers heat into the food. Moisture in the food is vaporized and forces its way to the food surface. The outside of the food, in addition to being browned by the heat of the oil, is puffed and crisped by this rapid moisture loss. Departing steam increases convection of the hot oil as it risest o the surface of the frypot; this convection and the high oil temperature cause the uniform and rapid cooking that is characteristic of frying. Fryers may take as little as ten to fifteen minutes to preheat, but they are typically turned on in the morning and left on throughout the day. Some operators use a backup fryer which is turned on as needed to handle increased demand during busy periods. Even in a busy fast food restaurant appliances may be idle 75% of the time.

2.3 TYPES OF FRYERS

2.3.1 Open Deep-Fat Fryers Open deep-fat fryers are by far the most common type. As FIGURE 2-2 A chicken/fish fryer. distinguished from pressure fryers, open fryers do not have a The vat is wide and sealed lid on the kettle and cook at atmospheric pressure. They shallow, and the basket is designed to are generally uninsulated, and lose heat from the surface of the hold one layer of oil and from the fryercabinet . Open fryersar e used to prepare food at a time. all types of fried food. Photo: Vulcan-Hart Company 2.3.2 Pressure Fryers Pressure fryers are less common. They are mainly used for preparing chicken, and are said to reduce moisture loss and oil uptake. The fryeri s similar to an open kettle fryerbu t with the addition of a heavy, gasketed lid and a pressure valve. As steam escapes fromth e food and builds up above the oil, the pressure inside the kettle rises. Moisture in the food reaches higher temperatures before escaping into the kettle, and cook time is somewhat decreased. Pressure fryers do incur some additional labor costs. Because of the locking lid, there are currently no pressure fryerswit h an automatic basket lift option. Opening and closing the lid adds extra steps to the cooking cycle and partially offsets the advantage of a shorter cook time. Food cannot be checked part way through the cycle, although this is not generally a problem with standardized recipes and procedures. Pressure fryers are

Technology Review of Commercial Foodservice Equipment Volume II, Page 2-2 more expensive to purchase, although the lid may provide some savings due to reduced heat loss during cooking and idle.

2.3.3 Specialty Fryers Most specialty fryershav e a rectangular or circular kettle with a deep cold zone at the bottom below the heat source. Specialty fryers include doughnut and chicken fryers, which are generally wide and shallow to allow a layer of food to float as it cooks. Instead of a standard fry basket, chicken and fish are generally lowered into the oil on a screen or shallow basket that is the same size as the top of the kettle. Donut fryers may have an upper "submerger" screen to immerse the doughnuts during frying.

2.4 CONTROLS Fryers are thermostatically controlled, and generally have an over limit switch to cut off energy to the burners or elements if the oil approaches its ignition point. Some fryers have a special FIGURE 2-3 "melt cycle" which toggles the burners on and off to melt solid Donut Fryer. Extremely wide and shortening without becoming hot enough to bum it. shallow, with a screen rather than a basket for cooking food. Thermostats sense the oil temperature with either a bulb or a Photo: solid state sensor. Bulb-type sensors use a working fluid which expands when heated, closing a valve or electrical contact. Solid-state sensors are more durable and accurate, but more expensive.

2.5 HEATING TECHNOLOGIES The energy performance within each category or type of fryer varies significantly; first depending on whether the fryer is gas or electric, and second based on the applied heating technology. Due to the many possible arrangements of the combustion and heat exchanger systems, there are greater differences in efficiencies among gas fryers on the market than among electric fryers. The usage of a fryer fromon e food service operation to another also impacts its energy efficiency and consumption. Both gas and electric fryers are less efficient under part-load operation due to the increased effect that the heat loss fromth e fryerha s on its efficiency. Gas fryers lose even more due to the part-load efficiency penalty that is characteristic of gas burners. Fryers also spend a significant portion of their operating time in stand• by or idle mode. Under such conditions, the energy efficiency of a gas fryerdrop s even further due to the short duty cycle of the

Technology Review of Commercial Foodservice Equipment Volume II, Page 2-3 burners. Under idle conditions, the energy consumed by a gas fryer may exceed an electric fryer's energy consumption by a D factor of three or more.1 2.5.1 Gas Gas fryers can be separated into two categories: standard and high efficiency. Standard gas fryers (the more common of the two) are designed with atmospheric or "blue-flame" burners with simple heat exchangers that either run through the frypot or underneath it. High efficiency gas fryers are fryers which take advantage of new developments in gas technology, such as infrared (IR) burners, heat pipes, pulse combustion, and recirculation tubes.

2.5.2 Electric Electric fryers typically use immersed elements in the frypot to provide heat to the frying oil. However, new developments in electric technology, such as the induction fryer, are beginning to change the landscape of the electric fryermarket . FIGURE 2-4 Fire tubes in the vat of a gas fryer. Typically burners fire into the tubes 2.5.3 Advanced Gas Fryer Technologies from the front, towards the flue at the A fairly wide bandwidth exists among gas fryer efficiencies. At ) rear of the fryer. The tubes may contain catalysts or baffles to increase the high end, various new technologies are incorporated into combustion efficiency. Infrared fryer design, yielding more efficient fryers with greater burners may also be mounted inside fire tubes. productivity. Among the new technologies already in place are Photo: Fisher Consultants powered infrared (IR) burners, recirculation tubes, and frypot insulation. Powered Infrared Burners. Powered infrared burners employ a fine honeycomb matrix to evenly disperse the fuel/air mixture across the burner surface. The mixture is delivered to the burner matrix by a forced draft blower which maximizes the fuel to air ratio. Combustion takes place close to the burner surface, causing it to become red-hot (approximately 980°C (1,800°F)) and emit infrared radiation to the surrounding heat transfer tube walls. In addition to the increased rate of heat transfer, IR burners operate with little excess air (less than 10%), allowing a greater percentage of gas to be burned than in a conventional atmospheric burner. Due to their potentially high first cost and maintenance cost, IR burners represent only 5% to 10% the gas fryers in the marketplace. Recirculation Tubes. Recirculation tubes, or recycle baffles, route the flue gasses through or around the sides of the frypot to provide a greater effective heat transfer surface for the hot

Technology Review of Commercial Foodservice Equipment Volume II, Page 2-4 gasses. More heat is transferred to the frying oil, yielding a 10% to 15% increase in efficiency. Pulse Combustion. Pulse combustion is a technology adapted from high efficiency boilers. The process is essentially a series of controlled explosions at a rate of 40 to 60 times a second, A forced draft blower initially delivers the fuel/air mixture to the combustion chamber, where it is ignited by a spark plug or glow coil. Once the combustion chamber heats up, the process becomes self-perpetuating and no longer requires the ignition device. The advantage of this technology is that it allows the use of a compact, highly efficient heat exchanger to deliver heat to the frying oil. Fryers with pulse combustion were too expensive to make run in the market place and still remain in the experimental stage. Convection/Thermal Fluids. Thermal fluids enable the use of an enclosed, highly efficient burner, independent of fryer design. A specially formulated oil acts as a medium to transfer heat fromth e burner to the frypot.Inefficiencie s in the heat transfer to the thermal fluid and the requirement of a specialized pump to circulate the fluid make this a less attractive possibility. Heat Pipe. Heat pipes are enclosed tubes that connect the heat source to the frypot. The tubes are filled with a working fluid that vaporize at the heat source end and condense at the end connected to the frypot. This technology requires extremely tight tolerances and was found too expensive to be successfully marketed.

2.5.4 Advanced Electric Fryer Technologies Induction Heating. Induction fryers use electromagnetic coils inside stainless steel immersion tubes. The electromagnetic field created by these coils induce eddy currents in the surrounding metal, causing it to heat up. The amount of heat generated is controlled by changing the frequency of the magnetic field in the coils. Induction technology is currently making its introduction into food service equipment market. There is currently one manufacturer of induction fryers. Frypot Insulation. Insulation around the frypotreduce s standby convective heat losses by as much as 25%. Frypot insulation is currently being applied to several high-end electric fryers. Apparently, manufacturers do not currently insulate their gas fryers due to safety limitations. Low Watt-Density Elements. Low watt-density elements provide an even distribution of heat to the frying oil by

Technology Review of Commercial Foodservice Equipment Volume II, Page 2-5 spreading the power across a greater surface area than standard cal rod elements. This enables the elements to provide quick temperature recovery without scorching the frying oil. Low watt-density elements are used in many electric fryerdesigns . Triac Controls. TRJAC controls provide electrical demand reduction and precise temperature control without the use of a mechanical contactor. The controller works in conjunction with a resistive thermal device (RTD) to modulate power to the elements during preheat and frying oil recovery. The TRIAC controller provides an effective, albeit expensive, solution to the electrical demand problem. The TRIAC controller is currently employed by only one manufacturer.

2.6 FRYER PERFORMANCE The work of the fryer can be outlined as bringing the oil from room temperature up to cooking temperature (preheating), holding the oil at cooking temperature until cooking begins (idling), and restoring heat to the oil when cold food is dropped into the fryer (recovery). An ASTM standard test method for fryers121develope d at Pacific Gas and Electric Company now allow manufacturers and users to gauge fryers' production directly, and to evaluate fryer energy performance as well. As hard data on fryers becomes available, it is apparent that certain technologies and designs yield better performance. The standard test method developed at PG&E quantifies energy input rate, preheat energy and time, idle energy rate, pilot energy rate, cooking energy rate and efficiency, frying medium recovery time and production capacity. Other factors that affect the actual performance of a fryer include fat capacity, ergonomics, ease of cleaning and quality of construction.

2.6.1 Energy Input Rate Energy input rate is one of the performance characteristics usually included in product literature. It is the maximum rate at which the fryer draws energy, expressed in kBtu/h or kW. Energy input rate is an important factor in production capacity. The more energy a fryer can deliver to the oil, the faster it can preheat and recover between loads. However, efficiency also plays an important part. A very efficient fryer may be able to supply more energy to the oil than an inefficient fryer with a higher energy input rate.

Technology Review of Commercial Foodservice Equipment Volume II, Page 2-6 2.6.2 Preheat Preheat Time. Preheat time is the time it takes to raise the oil from room temperature to cooking temperature. Fryers usually idle during the day, so preheat time may not be important to the operator. Preheat time is determined by energy input rate, oil capacity, heating technology and control strategy.

FIGURE 2-5 An example of a console fryer. The fryer on the right has a split vat; both have automatic basket lifts. The center is a fry station, for holding cooked product. In the cabinet below the fry station there is a built-in oil filter, which both fryers share. Photo: Vulcan-Hart Company

Preheat Energy. The energy required to preheat a fryer is a function of the oil capacity of the fryeran d its heat-up efficiency (probably close to its water-boil efficiency). However, preheat energy consumption represents less than 15% of the daily energy consumption for a fryer that was turned on twice over an 8-hour operating period. For longer fryer operations (e.g., 16 hours) with only one preheat, the energy performance of the fryer during this phase of its operation becomes less important.

Technology Review of Commercial Foodservice Equipment Volume II, Page 2-7 2.6.3 Idle Energy Consumption Both gas and electric fryers consume energy while holding the frying medium at the desired cooking temperature. This is due o to the heat that is lost fromth e surface of the oil or through the sides and bottom of the frypot. The idle-energy consumption rate is a function of the thermostat set point and the effective resistance of the fryer to heat loss. Monitoring the usage of fryers in commercial kitchens'31 has demonstrated that fryers spend a significant proportion of their "on time" in idle mode and that the rate of idle energy consumption has a significant impact on total daily energy consumption.

2.6.4 Cooking Energy Rate and Efficiency Cooking energy rate is the rate at which a fryer consumes energy while it cooks a load of food. It is reported in kBtu/h or kW. Cooking energy efficiency is the ratio of energy added to the food and total energy supplied to the appliance during cooking:

CookingEfficiency =flti'QOtl x 100% EApplioiice The ASTM standard test method defines cooking rates and efficiencies for heavy-load, medium-load and light-load conditions.

2.6.5 Production Capacity Production capacity is the amoimt of food that can be cooked in a fryer in a given time. For open fryers this figure typically given, in product literature and in the standard test method, as the number of pounds of frozen french fries that can be cooked per hour. Production capacity is determined by the cook time and the recovery time of the fryer. These in turn depend strongly on energy input rate, oil capacity, heating technology and control strategy.

2.6.6 Recovery Time Recovery time is the time it takes a fryert o come back up to cooking temperature after the food is lowered into the oil. It is determined by energy input rate, control strategy and the heating technology, among other factors.

Technology Review of Commercial Foodservice Equipment Volume II, Page 2-8 2.7 BENCHMARK ENERGY PERFORMANCE

2.7.1 Water-Boil Versus Cooking-Energy Efficiency Different definitions for energy efficiency make comparing fryers an even more complex task. Historically, the industry has relied on a water-boil efficiency to benchmark the performance of fryers. This efficiency is determined by operating the fryero n a large balance scale and boiling off a specified weight of water while at the same time measuring the energy consumed by the fryer. The efficiency is calculated by dividing the energy that was required to boil off the measured weight of water (based on 2256 kJ/kg (970 Btu/lb)) by the total energy consumed by the fryer. Water-boil efficiencies of 95%, 57% and 67% have been reported for an electric, gas atmospheric burner and gas infrared (IR) burner open deep-fat fryer, respectively. ] But a water-boil test does not emulate the operation of a fryer in a real food service operation. A fryer's job is to maintain a vat of oil at a relatively high temperature (e.g., 175°C (350°F)) while cooking food product. During this time, the burners or elements may cycle off as the thermostat is satisfied. But during a water-boil test the frypot temperatures cannot exceed 100°C (212°F). Furthermore, the thermostat is never satisfied during this test and the duty-cycle of the elements or burners remains at 100%. Thus, the credibility of a water-boil efficiency to reflect in-kitchen performance has been challenged by restaurant operators and the measure of actual cooking-energy efficiencies has evolved within the development of standardized test methods for the performance of fryers. '] In the calculation of a cooking-energy efficiency, the total quantity of energy transferred to the food product during the cooking process is calculated and divided by the total amount of energy consumed by the fryer. Reported cooking-energy efficiencies under heavy-load conditions (27 to 32 kg/h (60 to 70 lb/h)) are significantly lower (e.g. 15 percentage points) than the respective water-boil efficiencies. ] For example, the full-load, cooking-energy efficiencies for an electric, an atmospheric burner and an IR burner open deep-fat fryer were 81%, 45% and 50% compared to 95%, 57% and 67%, respectively. Under light-load testing (approximately 9 kg/h (20 lb/h)), the cooking energy efficiencies for these three fryers dropped further to 66%, 28% and 35% respectively. Although the light-load efficiencies are dramatically lower than the respective water-boil efficiencies for these fryers, they better reflect real-world energy performance where the average rate of cooking is typically less

Technology Review of Commercial Foodservice Equipment Volume II, Page 2-9 than 9 kg/h (20 lb/h). Therefore cooking-energy efficiencies have been selected over water-boil efficiencies for benchmarking the performance of gas and electric fryers for this o technology assessment. 2.7.2 Cooking-Energy Efficiency In support of the development of standard test methods for cooking appliances, a model has been reported that simplifies cooking appliance energy analysis.'41 This model, described as a two-mode model, is based on the assumption that any condition of appliance operation can be described as the sum of proportionate idle and heavy-load cooking operations, with preheat as an additional factor. The model therefore requires measurement of only preheat, idle and heavy-load cooking parameters. This model was based on work contained in U.S. Department of Energy regulations for hot water heaters and, with some limitations, is considered applicable to fryers. The model can be effectively applied to estimate part-load efficiencies for a fryer installation where only the operating time (e.g., 12h/day) and quantity of food cooked (e.g., 45 kg/day (100 lb/day)) is known. Table 2-1 summarizes the energy performance parameters for gas and electric open deep-fat fryers. Figure 2-7 and Figure 2-8 show the cooking energy JURE 2-6 efficiency curves for gas and electric open deep-fat fryers. Pressure fryer. Most pressure fryers have a heavy top and a round flat bottomed "kettle", like this one. Photo: Ballantyne Table 2-1 Energy Efficiency for 18-22 kg (40-50 lb) Capacity Open Deep-Fat Fryers

Electric Std. Gas High-EfTGas

Rated energy input (kBtu/h) 40-60 80-120 80 Cooking-energy Eff. (%) 75-85 25-50 50-60 Idle energy rate (kBtu/h) 2.5-3.5 10-15 5-10

Pressure fryers require a large vat and typically use a "bottom- fired" design. The benchmark performance of pressure fryers is somewhat lower than that of open deep-fat fryers. In fact, the high efficiency gas pressure fryers utilize atmospheric burners, as opposed to infrared burners in the open deep-fat fryers. Table 2-2 summarizes the energy performance parameters for gas and electric pressure fryers. Figure 2-9 and Figure 2-10 illustrate the

Technology Review of Commercial Foodservice Equipment Volume II, Page 2-10 -—^^i

0 10 20 30 40 50 60 Production Rate (lb/h)

FIGURE 2-7 GAS OPEN DEEP-FAT FRYER COOKING ENERGY EFFICIENCY CHARACTERISTICS.

90% High Efficiency

0% -' : 1 : 1 : ' . ! ! 1 ! 0 10 20 30 40 50 60 70 Production Rate (lb/h)

FIGURE 2-8. ELECTRIC OPEN DEEP-FAT FRYER COOKING ENERGY EFFICIENCY CHARACTERISTICS.

Technology Review of Commercial Foodservice Equipment Volume II, Page 2-11 cooking energy efficiency curves for gas and electric pressure fryers.

Table 2-2 Energy Efficiency for 14-22 kg (30-50 lb) Capacity Pressure Fryers

Electric Std. Gas High-EffGas

Rated energy input (kBtu/h) 30-50 55-80 40-60 Cooking-Energy Eff. (%) 65-85 25-35 35-50 Idle energy rate (kBtu/h) 1.5-4.0 10-15 4-10

60% • High Efficiency

0 10 20 30 40 Production Rate (lb/h)

FIGURE 2-9 GAS PRESSURE FRYER COOKING ENERGY EFFICIENCY CHARACTERISTICS.

Technology Review of Commercial Foodservice Equipment Volume II, Page 2-12 90% - High Efficiency Fryer 80% - >> o g 70% - | 60% w / i >. 50% - 2> I 40%" Typical Operating Low Efficiency Fryer g 30% ! Range 8 20% - O J 10% -/y 0% ' 0 10 20 30 40 Production Rate (lb/h)

FIGURE 2-10 ELECTRIC PRESSURE FRYER COOKING ENERGY EFFICIENCY CHARACTERISTICS.

2.7.3 Gas Versus Electric Fryer Performance Electric fryers typically use immersed elements to impart heat to the frying medium. This heating technology exhibits higher energy efficiencies due to the absence of the flue losses associated with gas fryers. Figure 2-11 and Figure 2-12 compare the gas and electric efficiency bandwidths for open deep-fat and pressure fryers.

2.8 FRYER ENERGY CONSUMPTION The 2-mode model can also be used to predict total daily energy consumption and/or the average rate of energy consumption for a given fryer. Figures 2-13 through 2-16 show estimated energy consumption rates and typical operating ranges for gas and electric open deep-fat and pressure fryers based on this model. Projected annual energy consumption for gas and electric fryers are presented in Table 2-3 and 2-4 based on the assumptions documented by the table footnotes. The information is based on test method development work for fryers at PG&E and proprietary end-use monitoring reports. The duty cycle is defined as the average rate of energy consumed expressed as a percentage of the rated energy input or the peak rate at which an appliance can use energy.

Technology Review of Commercial Foodservice Equipment Volume 11, Page 2-13 20 30 40 50 Production Rate (lb/h)

FIGURE 2-11 OPEN DEEP-FAT FRYER COOKING ENERGY EFFICIENCY BANDWIDTHS.

Electric

10 20 30 40 Production Rate (lb/h)

FIGURE 2-12 PRESSURE FRYER COOKING ENERGY EFFICIENCY BANDWIDTHS.

Technology Review of Commercial Foodservice Equipment Volume II, Page 2-14 100 Low Efficiency Fryer 90 - 80 - £3 70 - Typical Operating 0) To 60 - Range

w ra c o o O

10 20 30 40 50 60 Production Rate (Ib/h)

FIGURE 2-13 GAS OPEN DEEP-FAT FRYER ENERGY CONSUMPTION BASED ON THE TWO- MODE MODEL

50 - Low Efficiency Fryer 45 ■ € 3 40- ffi 35 Typical Operating 0) re 30 ■ Range ce >. 25 i 2> (D 20 C UJ o> c oO U

10 20 30 40 50 60 70 Production Rate (Ib/h)

FIGURE 2-14 ELECTRIC OPEN DEEP-FAT FRYER ENERGY CONSUMPTION BASED ON THE TWO-MODE MODEL

Technology Review of Commercial Foodservice Equipment Volume II, Page 2-15 60 Low Efficiency Fryer

€50 3 Typical Operating f 40 - Range ^ or \ ^ ^^—^ P»- ^fj^^ S SKi^ ,, ■^ IBBSB^ ^r**^ \ _^- ^""""^ \ c J£ i> o <31°- High Efficiency Fryer

n ' i ■■ 1— —i '— —i- 10 20 30 40 Production Rate (Ib/h)

FIGURE 2-15 GAS PRESSURE FRYER ENERGY CONSUMPTION BASED ON THE TWO-MODE MODEL

25 Low Efficiency Fryer

| 20 m Typical Operating Range

2> C 10 UJ DJ c 8 5 o

10 20 30 40 Production Rate (Ib/h)

FIGURE 2-16 ELECTRIC PRESSURE FRYER ENERGY CONSUMPTION BASED ON THE TWO- MODE MODEL

Technology Review of Commercial Foodservice Equipment Volume II, Page 2-16 TABLE 2-3 Projected Energy Consumption for Gas Fryers Oil Rated Duty Avg. Energy Typical Op Annual Energy Capacity Energy Input Cycle Consumption Hours Consumption (kBtu/h) (%) (kBtu/h) (h/d)a (kBtuf

OPEN DEEP FAT: Open Deep Fat 35-50 lb 80-120 (Median) 100 20 20° 12 74,900

PRESSURE/KETTLE: Pressure/Kettle 30-50 lb 40 - 80 (Median) 60 30 18" 10 56,600

FLAT BOTTOM: Chicken/Fish 125 1b 180 e (Median) 180 30 54 10 168,000

Donut 801b 60-76 (Median) 68 20' 14 34,900

'Operating hours or appliance "on time" is the estimated period of time that an appliance is typically operated from the time it is turned "on" to the time it is turned "off'. "The annual energy consumption calculation is based on the average energy use rate x the typical operating hours x 6 days per week x 52 weeks per year. The average energy consumption rate is based on a median production rate of iVt kg/h (10 Ib/h) generated from the two-mode energy model.'4' An associated duty cycle of 22% was calculated. The average energy consumption rate is based on a median production rate of A'A kg/h (10 Ib/h) generated from the two-mode energy model.Hl An associated duty cycle of 30% was calculated for a pressure/kettle fryer. CA 30% duty cycle has been assumed for flat bottom chicken/fish fryers based on the assumption that the usage pattern is similar to pressure/ kettle operations. Based on the duty cycle and the median energy input rate, an average energy consumption rate of 54 kBtu/h was calculated. fA 22% duty cycle has been assumed for flat bottom donul fryers based on the assumption that the usage pattern is similar to open deep-fat fryer operations Based on the duty cycle and the median energy input rate, an average energy consumption rate of 15 kBtu/h was calculated.

Technology Review of Commercial Foodservice Equipment Volume II, Page 2-17 TABLE 2-4 Projected Energy Consumption for Electric Fryers Vat Rated Duty Avg. Energy Typical Op. Annual Energy Capacity Energy Input Cycle Consumption Hours Consumption (kW) (%) (kW) (h/d)a (kWh)b (kBtu)c

OPEN DEEP FAT:

Open Deep Fat 35-50 lb 12-17 (Median) 15 20 3d 12 11,200 38,300

PRESSURE/KETTLE: Pressure/Kettle 30-50 9-14 (Median) 12 33 2e 10 6,200 21,300

FLAT BOTTOM:

Chicken/Fish 125 28?

(Median)

Donut 80 10-18

(Median) 14 14 2f 8 4,990 17,000

'Operating hours or appliance "on time" is (he estimated period of time that an appliance is typically operated fromth e time it is turned "on" lo the time it is turned "off'. The annual energy consumption calculation is based on the average energy consumption rate x the typical operating hours x 6 days per week x 52 weeks per year. 'Conversion Factor: I kW = 3.413 kBtu/h

The average energy consumption rate is based on a median production rate of 4'/2 kg (10 Ib/h) generated fromth e two-mode energy model.'4' An associated duty cycle of 15% was calculated. The average energy consumption rate is based on a median production rate of 4'/> kg (10 Ib/h) generated from the two-mode energy model.'4' An associated duty cycle of 12% was calculated for a pressure/kettle fryer. rA 20% duty cycle has been assumed for flat bottom donul fryers based on the assumption that the usage pattern is similar to open deep-fat fryer operations. Based on the duty cycle and the median energy input rate, an average energy consumption rate of 3 kW was calculated.

Technology Review of Commercial Foodservice Equipment Volume II, Page 2-18 Typical fryer usage involves one or two preheats over an 8 to 12 hour operating day. Figures 1-12 to 1-15 can be used to determine the average energy rate during operating hours for o each type of fryer. Annual energy consumption ranges for gas and electric open deep-fat and pressure fryersar e summarized in Tables 2-3 and 2-4. These ranges can be applied to demographic information to estimate the total annual fryer energy consumption for typical use in Canada.

2.8.1 Impact of Fryer Design on Oil Life The type of energy and its method of delivery to the frying oil has some effect on oil degradation; however documented studies indicate that the effect is overshadowed by the degradation caused by the type of food cooked in the fryer. '

2.8.2 Impact of Fryers on Exhaust Ventilation Rates and Kitchen Heat Gain Fryers tend to generate little effluent and therefore require low ventilation rates (95 to 140 L/s (200 to 300 cfrn) per linear foot). Due to their relatively low idle losses fryers introduce little heat to the space.

2.9 RESEARCH NEEDS Gas fryers have a large energy performance bandwidth, due in part to the prevalence of inexpensive, low efficiency burner FIGURE 2-17 designs. Additionally, fryers with a high heavy-load cooking 777/s gas "drop in" fryer can be built in to energy efficiency may still have significant idle losses. Since a countertop. It heats with venturi type most fryers are operated in the 4l/z to 9 kilogram per hour (10 to atmospheric burners that direct flame and flue gases through tubes 20 pounds per hour) range, many gains can be made by submerged in the frypot. Energy input improving the part-load efficiency of the fryerso n the market. for this type of fryer is 40-150 kBtu. Fryer part-load performance is primarily affected by the fryer's Photo: Pitco Frialator, Inc. standby losses. Reducing these losses with a minimal additional first cost will make a significant impact on total annual energy consumption, Potential research areas include: enhanced temperature control, frypot insulation, advanced atmospheric burners, pulse combustion, recirculation tubes, and/or fluedampers . Enhanced temperature control. Faster response, tighter temperature controls will better react to a cooking load, reducing fryer recovery time and temperature overshoot. Frypot insulation. Insulation around the frypot could reduce standby losses by as much as 25%.

Technology Review of Commercial Foodservice Equipment Volume II, Page 2-19 Advanced atmospheric burners. High efficiency atmospheric burners could dramatically reduce the energy consumption of gas fryers by performing the same amount of work with less o energy. Pulse combustion. Pulse combustion achieved high efficiencies and remarkable control. Further development of this concept with a lower first cost is needed. Recirculation tubes. Rerouting the flue gasses around and through the frypot increases the heat transfer surface, providing a 5% to 10% gain in efficiency. Applying this technology to advanced atmospheric burners may have a great effect on the baseline energy consumption of standard gas fryers. Two-stage burner. An atmospheric burner design with separate orifices for idle and full-input conditions could increase the burner's heat transfer efficiency when the fryer is in standby mode.

2.10 GAS INDUSTRY MARKET FOCUS First cost is a major factor in food service equipment purchases. New, energy efficient technologies have a high premium associated with them which deter many food service operators. The most attractive options for the gas industry involve the development of a lower first-cost,advance d atmospheric burner fryer with reduced standby losses.

2.11 REFERENCES 1. Pacific Gas and Electric Company. 1989. Development and Application of a Uniform Testing Procedure for Open, Deep-fat Fryers. Report 008.1-90.22 prepared for Research and Development, San Ramon, California. 2. American Society for Testing and Materials. 1992. Standard Test Methods for the Performance of Open, Deep-fat Fryers. ASTM Designation F1361-91, In Annual Book ofASTM Standards, Philadelphia. 3. Pacific Gas and Electric Company. 1990. Cooking Appliance Performance Report. Report 008.1-90.8 prepared for Research and Development, San Ramon, California, 4. Horton, D.J., Caron, R.N. 1994. Two-Mode Model for Appliance Energy Analysis. A presentation to the Society for the Advancement of Food Service Research, April. O

Technology Review of Commercial Foodservice Equipment Volume II, Page 2-20 5. Pacific Gas and Electric Company. 1990. Frying Medium Quality Life Determination. Report 008.1-90.20 prepared for Research and Development, San Ramon, California. 6. Pacific Gas and Electric Company. 1993. In-Kitchen Frying Medium Life Study. Report 008.1-92.16 prepared for Research and Development, San Ramon, California.

Technology Review of Commercial Foodservice Equipment Volume II, Page 2-21 3. GRIDDLES o 3.1 INTRODUCTION Griddles are used to make several of the most common meals on the food service menu: bacon and eggs, pancakes, hamburgers, steak and fish. For an operator shopping for a new griddle, the most important performance criteria is usually production capacity, i.e. the amount of food that can be cooked in a given time. For a high production fast food kitchen, temperature uniformity of the griddle surface is also important to assure that every burger is fully cooked. Market factors such as initial cost, warranty and manufacturer often affect appliance choice more than energy efficiency. Two factors are currently driving efficient design for griddles. First, large chains such as McDonald's have stimulated research on energy efficient griddles because they recognize the possibility of increasing profits by specifying better equipment. Second, ASTM standard test methods developed by Pacific Gas and Electric Company have allowed testing facilities to produce griddle energy performance data that can be compared between labs. This allows both manufacturers and purchasers to calculate the cost of operating specific griddle models and technologies. Published data shows that energy performance can vary significantly with griddle type and construction details. Griddles vary in size, power input, heating method, griddle plate construction and control strategy. All designs cook with a flat FIGURE 3-1. plate of metal which has splash guards attached to the sides and Typical of gas griddles commonly used rear and a shallow trough to guide grease and scraps into a across Canada, this 610 by 910 mm (24 by 36 in.) griddle is heated by three 24,000 holding tray. The griddle plate is heated from underneath by gas Btu/h steel burners which are manually burners or electric elements, and controls are generally on the adjusted with the controls visible on the frontfront of the appliance. Griddles may be freestanding floor of the unit. Photo: U.S. Range models, countertop units, or incorporated into a rangetop. The cooking surface is commonly 610 mm (24 in.) from frontt o back, but may be as shallow as 380 mm (15 in.) or as deep as 810 mm (32 in.) Widths range from 380 to 2130 mm (15 to 84 in.), and the griddle plate may be 15 to 30 mm QA to 1 lA in.) thick. Energy input rates vary from 20-180 kBtu/h for gas griddles and from 4-36 kW (14-123 kBtu/h) for electric griddles.

3.2 COOKING PROCESSES Griddles transfer heat to food by direct contact with the hot griddle plate. The desired characteristics of this style of cooking

Technology Review of Commercial Foodservice Equipment Volume II, Page 3-1 are crisping and browning, for foods like hashbrowns, bacon and pancakes; searing, for foods like hamburgers, steak, and fish; drying, for bread and buns. Griddle temperatures typically range from 95 to 230°C (200°F to 450°F), depending on the food being cooked. Because griddles can take as long as 25 minutes to preheat, they ^r&Jff are typically turned on at the beginning of the day and idled at cooking temperature. Some operators turn off sections of the griddle during slow periods to reduce idle energy use.

3.3 TYPES OF GRIDDLES

3.3.1 Single-sided Griddles The most common type of griddle is a single-sided griddle with a flat griddle plate, heated by atmospheric burners. Burners are usually spaced 200-300 mm (8-12 in.) apart with one control per burner. This allows each section of the griddle to be maintained FIGURE 3-2. at a different temperature for different foods, or turned off Manufacturers commonly offer griddles as during slow periods. a component of a restaurant range. This model from Vulcan-Hart Company 3.3.2 Grooved Griddles combines a small griddle with an open-top 7e, broiler and a standard oven. Some manufacturers offer grooved griddle plates as an option. Jo: Vulcan-Hart Company These allow the operator to serve food that has the characteristic striped sear mark of a charbroiler without the broiler's high energy cost or the increased ventilation requirements due to a broiler's smoke and heat. The grooves also drain away some of the grease that forms during cooking. Less of a grooved griddle's surface contacts the food and transfers heat, so chefs may set the griddle temperature higher to compensate. As the grooved surface is not appropriate for popular foods such as eggs, pancakes and sandwiches, some griddle plates are manufactured with both grooved and flat sections.

3.3.3 Chrome-Finished Griddles Several manufacturers now offer griddles with a chrome- finished cooking surface. Such a surface is easier to clean and radiates less heat towards the chef and the kitchen. In addition FIGURE 3-3. to being more comfortable for the chef, this may produce some Gas griddle with a grooved plate. Spacing on the grooves is generally 13 mm (Vi in.) direct energy savings by lowering heat loss during idle and cooking, and indirect savings in the cost of cooling the kitchen. Photo: U.S. Range Both flat and grooved griddles are available with a chrome finish.

Technology Review of Commercial Foodservice Equipment Volume II, Page 3-2 3.3.4 Double-Sided Griddles and Duplex Cookers Double-sided griddles were developed for fast food chains that wanted to shorten cook time and increase production of hamburgers. A two-sided griddle has a hinged upper griddle plate that swings down to contact the food so that it cooks from both sides at once. The upper section has a manual or automatic adjustment for the size of food being cooked. The upper griddle plates are most often electrically heated, even if the lower section uses gas. The Lang DSG™ is an exception. This double- sided griddle circulates gas-heated oil to both the upper and lower griddle plates. Duplex cookers are similar to double sided griddles, except that the top section is a broiler instead of a griddle plate (Figure 3-4), When the upper platen is lowered over the food, the broiler stays a few inches above the griddle and cooks with infrared heat. The radiants in the broiler may be either gas or electric. Both types of griddles cook hamburger patties twice as fast as a single-sided griddle. The operator fills orders faster and saves the labor involved in tending the griddle and flipping burgers. In

FIGURE 3-4. This duplex cooker incorporates gas radiants into the hooded upper section. The radiants automatically come to full power when the hood is lowered. Clearance between the radiants and the griddle is 75 mm (3 in.) Photo: Lang Mfg. Co.

Technology Review of Commercial Foodservice Equipment Volume II, Page 3-3 addition, these griddles are energy efficient. A duplex cooker or double sided griddle can produce the same amount of food per hour as a larger conventional griddle. Its smaller surface area 3 has lower radiant and convective energy losses during idle and cooking. The top sections further reduce heat loss by acting as a cover when they are in the closed position. Duplex and double sided griddles have a high initial cost and require more maintenance. Energy savings alone will probably not make up for the price difference. However, for a high- volume operation the increased production capacity, reduced labor and shorter customer response time justify the higher initial cost.

3.4 CONTROL STRATEGIES Griddle controls are generally simple. The temperature of each section is controlled manually or with a thermostat. Manual controls are analogous to the familiar controls on a gas rangetop burner: the height of the flame is adjusted directly to set temperature. Thermostats improve surface temperature uniformity and prevent temperature overshoot; this is especially valuable on high-input griddles, where overheating can occur quickly and cause permanent damage to the griddle plate. Thermostats sense the griddle temperature with either a bulb or a solid state sensor. One sensor is usually mounted underneath or embedded into each section of the griddle plate. Bulb-type sensors use a working fluid which expands when heated, closing a valve or electrical contact. Solid-state sensors are more durable and accurate, but more expensive. In a snap-action thermostat, the sensors toggle each griddle section between full energy input and no input. Modulating or throttled thermostats adjust the energy input incrementally to achieve "soft landing" at the setpoint temperature without overshoot. Modulating thermostats are less expensive, but they are not as accurate in maintaining constant temperatures throughout the cook cycle and across griddle sections. Very few griddles incorporate timers or elaborate "cooking computers". Doneness is usually determined by the chef, who decides based on experience when to turn the food and how to compensate for uneven heating and varying cook times. The Lang double sided griddle attempts to control surface temperature and uniformity closely enough that the cooking process can be automated and the operator's attention spared. This griddle uses solid-state controls and cooking computers that can be programmed with temperatures and times for

Technology Review of Commercial Foodservice Equipment Volume II, Page 3-4 several different food products. The computers may be programmed on site, or remotely through an optional modem in the griddle.

3.5 HEATING TECHNOLOGIES All varieties of griddle (flat, grooved, double-sided, chromium- finished) are available in both gas and electric models. For each fuel source, there are different strategies for applying heat to the griddle: open flame atmospheric burners, infrared burners and heat pipe technology for gas; standard elements and induction heating for electricity. Even among appliances that use the same heating technology, there can be large variations in energy use due to appliance design. The usage of a griddle from one food service operation to another also impacts its energy efficiency and consumption. Both gas and electric griddles are less efficient under part-load operation due to the increased effect that the heat loss from the cooking surface has on appliance efficiency. Gas griddles lose even more due to the part-load efficiency penalty that is characteristic of gas burners. Griddles also spend a significant portion of their operating time in stand-by or idle mode. Under such conditions, the energy efficiency of a gas griddle drops even further due to the short duty cycle of the burners,

3.5.1 Gas Gas griddles can be separated into two categories: standard and high efficiency, Standard gas griddles (the more common of the two) are designed with atmospheric or "blue-flame" burners located directly below the griddle plate. High efficiency gas griddles are griddles which take advantage of new developments in gas technology, such as infrared (IR) burners, heat pipes, and thermal fluid.

3.5.2 Electric Electric griddles use heating elements that are attached to the bottom of the griddle plate or embedded into it. Depending on the pattern of the elements, surface temperature uniformity can be very good from edge to edge. New technologies, such as the induction griddle, are highlighting the temperature uniformity as a desirable performance parameter.

Technology Review of Commercial Foodservice Equipment Volume II, Page 3-5 3.5.3 Advanced Gas Griddle Technologies Gas griddles are far more common than electric griddles. There are several different burner types currently in use and under development.

Atmospheric burners. Atmospheric burner griddles represent the low end of the heavy-load cooking efficiency range for griddles. However, a high-end atmospheric gas griddle approaches the performance of an infrared griddle in heavy-load cooking efficiency and idle energy consumption rate.

Infrared burners. Infrared burners are more expensive and generally more efficient. Gas griddles employ infrared radiants that force gas through a ceramic block perforated with thousands of small holes. Combustion takes place close to the burner surface, causing it to become red-hot (approximately 980°C (1,800°F)) and emit infrared radiation to the underside of the griddle plate. Due to their potentially high first cost and maintenance cost, IR burners represent only 5% to 10% the gas griddles in the marketplace. This technology offers increased potential for good surface temperature uniformity, and has outperformed comparable atmospheric griddles in heavy, medium, light load and idle tests.

Thermal Fluid. GR1 and Lang Manufacturing Company have developed a griddle heated by circulation of hot oil (Figure 3-5). This technology makes gas heat easy to distribute across the griddle surface and to the upper plate of a double-sided griddle. It takes advantage of well-developed methods for applying gas heat to a liquid, which in devices such as boilers and booster heaters have proven to be very cost effective. Additionally, thermal fluid technology allows for better distribution of heat across the griddle plate, yielding greater uniformity.

Pulse Combustion. Pulse combustion is a technology adapted from high efficiency boilers. The process is essentially a series of controlled explosions at a rate of 40 to 60 times a second. A forced draft blower initially delivers the fuel/air mixture to the combustion chamber, where it is ignited by a spark plug or glow coil. Once the combustion chamber heats up, the process becomes self-perpetuating and no longer requires the ignition device. The advantage of this technology is that it allows the use

Technology Review of Commercial Foodservice Equipment Volume II, Page 3-6 FIGURE 3-5. Lang's heat pipe griddle, the Lang DSG (Double Sided Griddle). The controls are computerized, and can be pre-programmed for several different foods. The upper platens adjust to the food automatically. Photo: Lang Mfg of a compact, highly efficient heat exchanger to deliver heat to the griddle plate. Griddles with pulse combustion were too expensive to make run in the market place and still remain in the experimental stage.

Heat Pipe. Heat pipes are enclosed tubes that connect the heat source to the griddle plate. The tubes are filled with a working fluid that vaporize at the heat source end and condense at the end connected to the griddle plate. Like the thermal fluid griddle, heat pipe technology has the potential to evenly distribute heat across the griddle plate, yielding good temperature uniformity. This technology requires extremely tight tolerances and was found too expensive to be successfully marketed.

Technology Review of Commercial Foodservice Equipment Volume II, Page 3-7 3.5.4 Advanced Electric Griddle Technologies Electric griddles are generally more efficient than gas griddles, but in most areas have higher energy costs.

Standard Elements. Standard electric griddles use heating elements that are attached to the bottom of the griddle plate or embedded into it. Placement of the elements affects surface temperature uniformity. One manufacturer uses a loop element near the perimeter of the griddle to reclaim the area where temperature usually falls off due to radiant losses fromth e sides of the griddle plate.

Infrared Heat Panels. Infrared heat panels have greater control over the distribution of heat than standard elements. Electricity runs through a filament wound back and forth through a ceramic composite block. The block heats evenly, allowing for a uniform cooking surface.

Induction. Induction technology has been developed for griddles, but not successfully marketed. Induction griddles use an induction coil below the griddle plate to generate field that induces a current in the plate itself. This current heats up the plate with little energy lost in the transmission from coil to plate, and the griddle temperature can be regulated by adjusting the current in the coil. In a variation on this technology, the griddle temperature is regulated by the plate itself. The plate is built with a metal alloy whose Curie point is near the desired cooking temperature. When the plate reaches its Curie point, it loses its magnetic properties and stops drawing energy. This characteristic allows induction griddles to provide a constant temperature across the cooking surface. Also, when food draws heat fromth e griddle, the cooled plate can again gain energy from the magnetic field. The area of the griddle plate directly under the food falls below the Curie point and becomes magnetic. The plate "senses" the food's presence and generates an amount of heat sufficient to replace what it transfers to the food. Metcal, Inc. has built a prototype induction griddle based on the temperature-limiting alloy plates. Each section of the griddle is a 300 mm (12 in.) wide removable plate with a fixed temperature setpoint. The operator selects and arranges plates to configure different temperature zones for the griddle. Metcal

Technology Review of Commercial Foodservice Equipment Volume II, Page 3-8 reports a cooking energy efficiency of 80%, well above the best reported figure of 70% for a standard electric griddle. They also report good surface temperature uniformity and a two minute preheat. Induction technology holds promise for electric griddle performance and efficiency. However, it is likely to remain a very expensive type of griddle due to the cost of the induction coils and, for some induction griddles, the cost of fabricating the griddle plate.

3.6 GRIDDLE PERFORMANCE The ASTM standard test method for griddles1'1 quantifies energy use and efficiency, surface temperature uniformity and production capacity. Other factors that may affect the actual performance of a griddle include ergonomics, ease of cleaning and quality of construction.

3.6.1 Input Rating Input rating is the performance characteristic usually included in product literature. It is the maximum rate at which an appliance draws energy, expressed in kBtu/h or kW. Energy input rate varies from 20-180 kBtu/h for gas griddles, 4-36 kW (14-123 kBtu/h) for electric griddles. The more power a griddle has, the faster it can preheat and recover between loads. This is important for achieving high production capacity.

3.6.2 Surface Temperature Uniformity Surface temperature uniformity is the ability to maintain the desired temperature across the entire surface of the griddle, without hot or cold spots that the chef must work around. Typically surface temperature falls off on the perimeter of the griddle, due to radiant losses from the sides and burner/element positioning. Temperature uniformity is affected by type and placement of burners or elements, griddle thermostat and controls and the thickness of the griddle plate. A thicker griddle plate will distribute heat more evenly, but has the disadvantages of additional cost and slower response to the controls.

3.6.3 Preheat Energy Consumption The energy required to preheat a griddle is a function of the size of the griddle plate and its heat-up efficiency. However, preheat energy consumption represents less than 15% of the daily

Technology Review of Commercial Foodservice Equipment Volume II, Page 3-9 energy consumption for a griddle that was turned on twice over an 8-hour operating period/ For longer griddle operations (e.g., 12 hours) with only one preheat, the energy performance of the griddle during this phase of its operation becomes less important.

3.6.4 Idle Energy Consumption Both gas and electric griddles consume energy while holding the griddle plate at the desired cooking temperature. This is due to the heat that is lost from the cooking surface or through the sides of the griddle. The idle-energy consumption rate is a function of the thermostat set point and the effective resistance of the griddle to heat loss. Monitoring the usage of griddles in commercial kitchens has demonstrated that griddles spend a significant proportion of their "on time" in idle mode and that the rate of idle energy consumption has a significant impact on total daily energy consumption/ J

3.6.5 Cooking Efficiency Cooking efficiency is defined in the ASTM test method for heavy-load, medium-load and light-load conditions. It is reported as the ratio of energy added to the food and total energy supplied to the appliance during cooking:

Ef ad CookingEfficiency = x 100% il, Appliance Heavy-load cooking energy efficiencies for gas griddles vary from 25%-45%. For electric griddles, the range is 60%-70%.

3.6.6 Production Capacity Production capacity is the amount of food that can be cooked on a griddle in a given time. For griddles this figure is commonly reported as the number of pounds of frozen hamburger patties that can be cooked per hour. For single-sided griddles, production capacity is most strongly linked to the size of the griddle plate.

3.6.7 Recovery Time Recovery time is the time it takes a griddle to come back up to cooking temperature after the previous load has been cooked. It is determined by energy input rate, control strategy and the thickness of the griddle plate. Slow recovery time reduces the production capacity of a griddle. Reported recovery times range from less than one minute to over seven minutes.

Technology Review of Commercial Foodservice Equipment Volume II, Page 3-10 3.7 BENCHMARK ENERGY PERFORMANCE

3.7.1 Water-Boil Versus Cooking-Energy Efficiency In the body of published data on griddles, two different tests are commonly reported as "cooking efficiency" tests: a water-boil test, in which a dam is built on the griddle surface to contain a set quantity of water which is weighed before and after boiling for a set period of time, and a test in which frozen hamburger patties are cooked. Water-boil efficiencies of 88%, 44% and 51% have been reported for an electric, gas atmospheric burner and gas infrared (IR) burner 910 mm (36 in.) griddle, respectively, whereas cooking-energy efficiencies under heavy-load conditions for the same griddles were 65%, 31% and 42%. But a water-boil test does not emulate the operation of a griddle in a real food service operation. A griddle's job is to maintain a cooking surface at a relatively high temperature (e.g., 190°C (375°F)) while cooking food product. During this time, the burners or elements may cycle off as the thermostat is satisfied. But during a water-boil test the cooking surface temperatures cannot exceed 100°C (212°F). Furthermore, the thermostat is never satisfied during this test and the duty-cycle of the elements or burners remains at 100%. The ASTM method now uses the more representative hamburger patty test exclusively.

3.7.2 Cooking-Energy Efficiency In support of the development of standard test methods for cooking appliances, a model has been reported that simplifies cooking appliance energy analysis. This model, described as a two-mode model, is based on the assumption that any condition of appliance operation can be described as the sum of proportionate idle and heavy-load cooking operations, with preheat as an additional factor. The model therefore requires measurement of only preheat, idle and heavy-load cooking parameters. This model was based on work contained in U.S. Department of Energy regulations for hot water heaters and, with some limitations, is considered applicable to griddles. The model can be applied to estimate part-load efficiencies for a griddle installation where only the operating time (e.g., 8h/day) and quantity of food cooked (e.g., 45 kg/day (100 lb/day)) is known, assuming that the entire griddle is left on during operating hours. Table 3-1 summarizes the energy performance parameters for gas and electric griddles. Figure 3-6 and Figure

Technology Review of Commercial Foodservice Equipment Volume II, Page 3-11 3-7 show the cooking energy efficiency curves for gas and o electric griddles. Table 3-1 Energy Efficiency for 910 mm (36 in.) Griddles

Electric Std. Gas High-Eff Gas

Rated energy input (kBtu/h) 25-60 40-80 60-80 Cooking-energy Eft (%) 65-75 25-35 40-50 Idle energy rate (kBtu/h) 5-9 15-20 10-15

High Efficiency 50% - Griddle 45% - 40% - c a Typical Operating o 35% - Range e 30% - LU >. 25% .- E» 15 % - C 12 o 10% 1 o o 5% - 0% 0 10 20 30 40 Production Rate (Ib/h)

FIGURE 3-6 GAS 910 MM (36 IN.) GRIDDLE COOKING ENERGY EFFICIENCY CHARACTERISTICS.

Technology Review of Commercial Foodservice Equipment Volume II, Page 3-12 80% n,a' ■1.1GI iwy Griddle 70% - o c 60% _ TyP'cal Operating § Range jrf*' ^J*-" jfj 50% - V B ^^-^^"^ \ a J$? p 40% i X c /* Low Efficiency Griddle ro 30% - / c / Er : g 20% - / r o // 10% - /

0% ' 0 10 20 30 40 Production Rate (Ib/h)

FIGURE 3-7 ELECTRIC 910 MM (36 IN.) GRIDDLE COOKING ENERGY EFFICIENCY CHARACTERISTICS.

3.7.3 Gas Versus Electric Griddle Performance Electric griddles typically use elements either located directly below or embedded in the griddle plate to impart heat to the cooking surface. This heating technology exhibits higher energy efficiencies due to the absence of the flue losses associated with gas griddles. Figure 3-8 compares the gas and electric efficiency bandwidths for 910 mm (36 in.) griddles.

Technology Review of Commercial Foodservice Equipment Volume II, Page 3-13 60% - 70% Electric I 60% e 50%

B 40% a> "if. 30% c o 20% o O 10% 0% 0 10 20 30 40 Production Rate (Ib/h)

FIGURE 3-8 910 MM (36 IN.) GRIDDLE COOKING ENERGY EFFICIENCY BANDWIDTHS.

3.8 GRIDDLE ENERGY CONSUMPTION

3.8.1 Average Energy Consumption Rate The two-mode model can also be used to predict total daily energy consumption and/or the average rate of energy consumption for a given griddle. Figure 3-9 and Figure 3-10 show estimated energy consumption rates and typical operating ranges for gas and electric 910 mm (36 in.) griddles based on this model.

Technology Review of Commercial Foodservice Equipment Volume II, Page 3-14 Low Efficiency Griddle

10 20 30 40 Production Rate (Ib/h)

FIGURE 3-9 GAS 910 MM (36 IN.) GRIDDLE ENERGY CONSUMPTION BASED ON THE TWO- MODE MODEL

30 Low Efficiency Griddle

10 20 30 40 Production Rate (Ib/h)

FIGURE 3-10 ELECTRIC 910 MM (36 IN.) GRIDDLE ENERGY CONSUMPTION BASED ON THE TWO-MODE MODEL

Technology Review of Commercial Foodservice Equipment Volume II, Page 3-15 3.8.2 Energy Use Models Typical griddle usage involves one or two preheats over a typical operating day. Average energy consumption rates for 910 mm O (36 in.) griddles cooking an average of 4!4 kilograms (10 pounds) per hour over 12 hours of operation were determined from Figure 3-9 and Figure 3-10. The projected range in annual energy consumption for gas and electric 910 mm (36 in.) griddles is illustrated in Figure 3-11.

140

120 - 3 m o 100 - g X 80 -

U)>. 0) 60 c HI m 40 C3 c < 20 -

Elec Std. Gas Hrgh-Eff Gas

FIGURE 3-11. GRIDDLE ENERGY CONSUMPTION RANGES.

3.8.3 Projected Annual Energy Consumption Projected annual energy consumption for gas and electric griddles is presented in Table 3-2 and Table 3-3. Energy consumption were based on duty cycles of 30% for gas and 25% for electric as determined from Figure 3-9 and Figure 3-10. The duty cycle is defined as the average rate of energy consumption expressed as a percentage of the rated energy input or the peak rate at which an appliance can use energy.

Technology Review of Commercial Foodservice Equipment Volume II, Page 3-16 TABLE 3-2 Projected Energy Consumption for Gas Griddles Nominal Rated Energy Duty Avg. Energy Typical Annual Energy Size Input Cycle Consumption Op. Hours Consumption (kBtu/h) (%) (kBtu/h) (h/d)a (kBtu)b

Single Sided 36 in. 60 - 80

(Median) 70 34 23c 12 86,100

"Operating hours or appliance "on time" is the estimated period of time that an appliance is typically operated from the time it is turned "on" to the lime it is turned "off'. "The annual energy consumption calculation is based on the average energy use rate x the typical operating hours x 6 days per week x 52 weeks per year. 'The average energy consumption rate is based on a median production rate of 4Vi kg (10 Ib/h) generated from the two-mode energy model.14' An associated duty cycle of 34% was calculated.

TABLE 3-3 Projected Energy Consumption for Electric Griddles Nominal Rated Duty Avg. Energy Typical Annual Energy Size Energy Input Cycle Consumption Op. Hours Consumption (kW) (%) (kW) (h/d)a (kWh)b (kBtu)

Single Sided 36 in. 8-16

(Median) 12 25 3d 12 11,232 38,300

"Operating hours or appliance "on time" is the estimated period of time that an appliance is typically operated from the time it is turned "on" to the time it is turned "off. 'The annual energy consumption calculation is based on the average energy consumption rate x the typical operating hours x 6 days per week x 52 weeks per year. "Conversion Factor: I kW = 3.413 kBtu/h dThe average energy consumption rale is based on a median production rale of 4'/i kg (10 lb/h) generated from the two-mode energy model.'"1 An associated duty cycle of 25% was calculated.

Technology Review of Commercial Foodservice Equipment Volume II, Page 3-17 3.9 VENTILATION REQUIREMENTS The effluent generated by a griddle depends on the type of food being cooked. For example, hamburgers generate significantly more effluent than pancakes or hash brown potatoes. Since there is the potential for a high amount of grease laden air, griddles can require ventilation rates in the range of 120 to 165 L/s (250 to 350 cfm) per linear foot of wall-mounted canopy. The large cooking surface tends to be a good radiator of heat to the kitchen space. Typical griddles with polished steel griddle plates have a high emissivity and may represent a significant load on the ventilation system. Griddles are now being offered with chrome-finished cooking surfaces which have a low emissivity. Such a surface will reduce the thermal load to the kitchen space.

3.10 RESEARCH NEEDS Gas griddles have a large energy performance bandwidth, due in part to the prevalence of inexpensive, low efficiency burner designs. Additionally, griddles with a high heavy-load cooking energy efficiency may still have significant idle losses. Since most griddles are operated in the 2lA to 7 kilograms (5 to 15 pounds) per hour range, many gains can be made by improving the part-load efficiency of the griddles on the market. Griddle part-load performance is primarily affected by the griddle's standby losses. Reducing these losses with a minimal additional first cost will make a significant impact on total annual energy consumption. Potential research areas include: enhanced temperature control, advanced atmospheric burners, pulse combustion, heat pipes, and low emissivity griddle plates.

Enhanced Temperature Control. Faster response, tighter temperature controls will better react to a cooking load, reducing griddle recovery time and temperature overshoot.

Advanced Atmospheric Burners. Improved efficiency atmospheric burners, coupled with heat fins on the bottom of the griddle plate to distribute heat could significantly reduce the energy consumption of gas griddles. The griddle could perform the same amount of work with less energy.

Technology Review of Commercial Foodservice Equipment Volume II, Page 3-18 Advanced atmospheric burners have a great potential for impacting the overall energy consumption due to their relatively low incremental cost.

Pulse Combustion. Pulse combustion achieved high efficiencies and remarkable control. Further development of this concept with a lower first cost is needed.

Heat Pipes. Heat pipes have the potential to generate highly uniform cooking surfaces. Development of a lower first-cost heat pipe griddle is needed.

Low Emissiviry Griddle Plates. Due to rising ventilation costs, heat gain is becoming more of an issue. Use of chromium or other metals to reduce radiant losses not only improve cooking energy efficiency, but reduce ventilation load.

Two-Stage Burner. An atmospheric burner design with separate orifices for idle and full-input conditions could increase the burner's heat transfer efficiency when the griddle is in standby mode,

3.11 GAS INDUSTRY MARKET FOCUS First cost is a major factor in food service equipment purchases. New, energy efficient technologies have a high premium associated with them which deter many food service operators. The most attractive options for the gas industry involve the development of a lower first-cost, advanced atmospheric burner griddle with reduced standby losses.

3.12 REFERENCES 1. American Society for Testing and Materials. 1991. Standard Test Methods for the Performance of Griddles. ASTM Designation 1275-90, In Annual Book of ASTM Standards, Philadelphia. 2. Pacific Gas and Electric Company. 1990. Cooking Appliance Performance Report. Report 008.1-90.8 prepared for Research and Development, San Ramon, California. 3. Pacific Gas and Electric Company. 1989. Development and Application of a Uniform Testing Procedure for Griddles.

Technology Review of Commercial Foodservice Equipment Volume II, Page 3-19 Report 008.1-89.2 prepared for Research and Development, San Ramon, California. 4. Horton, D.J., Caron, R.N. 1994. Two-Mode Model for Appliance Energy Analysis. A presentation to the Society for the Advancement of Food Service Research, April.

Technology Review of Commercial Foodservice Equipment Volume II, Page 3-20 4. BROILERS

> 4.1 INTRODUCTION

This section of the report describes the most common types of broilers: underfired (charbroilers), overtired (upright broilers, salamanders and cheesemelters,) and conveyor broilers. Charbroilers can cook high volumes of meat and seafood with the characteristic smoke and flame that make them a showpiece as well as a workhorse. They are similar to a barbecue in that food is cooked on a grid placed over a radiant heat source. Up• rights, salamanders and cheesemelters are overfired broilers: they apply heat from above the food, and produce much less smoke and flame. Overfired broilers range in size and ability

FIGURE 4-1 from those that can prepare thick steaks in quantity to those in• A gas underfired charbroiler. The lower grid tended only for melting cheese and browning food. High pro• allows this appliance to work as a cheese- duction broiling in most kitchens is handled by overfired up• melter type overtired broiler as well. Photo: Magikitch'n, inc. right broilers. By design, broilers are open to the kitchen and therefore radiate a great deal of heat into the room. They tend to have high en• ergy use and low efficiency, and represent one of the most ex• pensive appliances to operate in a commercial kitchen. In addi• tion, broiling-especially underfired broiling on a charbroiler- produces more smoke than comparable cooking methods such as griddles. However, the flavor and appearance of broiled food is distinctive, and is often a selling point on the menu. A significant innovation to come to market in recent years is the mechanized or conveyor broiler favored by high-volume fast- food chains due to its high production capacity. Combination broiler/griddles such as the Clamshell® are well suited to op• erations with varied menus such as family-style and steak or seafood restaurants. Broilers are used to prepare steak, fish, chicken, shishkebab and seafood as well as to brown food such as casseroles, to finish au gratin dishes and meringues, to reheat plated food and to melt cheese toppings. The desirable characteristics of broiling are striping (the marks created by the hot grill or "grid"), browning, searing, charring, crisping, and for cheese, melting. Some appli• cations are only appropriate for certain types of broilers. Con• struction details and specific applications for each type are dis• cussed under Types of Broilers.

Technology Review of Commercial Foodservice Equipment Volume IJ. Page 4-1 4.2 COOKING PROCESSES The terms "underfired" and "overfired" refer to the position of a broiler's heat source relative to the food. In both cases the food is cooked using radiant heat, although the heat source may vary. All broilers use a "grid", which is the grill or grate on which the food is placed for cooking. When the broiler is standing by, the grid absorbs heat from the burners or elements which is then conducted to the food. In most types of broilers, the grid is hot enough to sear a pattern into the food, and this is the most iden• tifiable visual characteristic of broiling. Gas is by far the most common fuel source. Some broilers use electric radiants or elements, and a few charbroilers use coal or wood for heat. Broilers are often idled throughout the day since they require preheating, which may take from 90 seconds to more than thirty minutes, depending on broiler type and design.

4.3 CONTROLS Most broilers do not use thermostats or timers to control the cooking process, and so demand the attention and experience of the chef Heat to food is adjusted by regulating energy input to the broiler and changing the placement of the grid, or food on the grid. Operators become familiar with hot and cold areas on the grid through experience, and these may be varied by adjust• ing the height of the grid in overfired broilers and by slanting the grid in some underfired charbroilers. Input is regulated manually with one or two controls on overfired broilers and of• ten one control per burner on charbroilers. Conveyorized broilers are an exception in that they do employ sophisticated controls. With this type of broiler, the cook time and temperature are selected by the operator. Some convey• orized broilers have cooking computers that store time and tem• FIGURE 4-2 perature parameters for several products so that the operator This underfired gas charbroiler has one con• need only load the broiler and press the appropriate button. trol for each burner; some charbroilers group burners into one or several zones. Total in• put for the 1016 mm (40") wide grid is 4.3.1 Energy conservation strategies 126kBtu/h or about 26 kStu/h for every square foot of grid, a typical rate for this type Broilers usually idle at full input so that they are ready to cook of broiler. Photo: Baker's Pride, Ltd. the instant they are needed. As a compromise between readiness and economy, some operators turn down the input to the broiler or turn off some sections altogether during slow periods; this can save significant amounts of energy. Some manufacturers have designed broilers with a weight-sensitive feature that turns the broiler down or off entirely until food is placed on the grid, when the broiler returns to full input. So far this strategy has

Technology Review of Commercial Foodservice Equipment Volume II, Page 4-2 only been applied to a few of the smaller overfired broilers (salamanders and cheesemelters.) One manufacturer makes an accessory for gas charbroilers that allows broilers to idle at less than their full input rate without incurring a significant preheat time. The "Broil-Master®" re• duces gas flow when the broiler is on, but not cooking food. When the operator is ready to cook, he pushes a button that re• stores full input to the broiler. The Broil-Master maintains this rate for a specified amount of time (e.g. 10 minutes) that covers most cooking events. If more food product is added to the grid, the operator can push the button again to continue cooking,

4.4 TYPES OF BROILERS FIGURE 4-3 There are two major categories of broilers: underfired and over• This cutaway view of a standard underfired gas charbroiler shows a fired. Here the overfired category is further divided into up• layer of rock used to diffuse flame rights, salamanders and cheesemelters, following typical indus• from the gas burners; lava rock and try usage. Conveyorized broilers, which use burners on both ceramic briquettes are commonly used. The rock is placed on a grate sides of the food product at once, are treated as a third category. above the burners and below the Additional material describes a hybrid broiler/griddle combina• food grid. As it heats up, the rock tion. radiates heat and burns drippings from the food. Photo. Magikitch'n, Inc. 4.4.1 Underfired Broilers Underfired broilers are commonly referred to as charbroilers and hearth broilers. They have the highest input rate and pro• duction capacity among broiler categories (with the possible exception of some conveyor broilers.) They resemble the famil• iar barbecue, using a heat source below a sturdy metal grid to Stale- uuw cook food with a combination of radiant heat, conduction and convection. Charbroilers are showy appliances that produce flames and smoke while cooking, and are often positioned in the kitchen so that these effects will be visible to patrons. The char• broiler marks food with a distinctive lined pattern, and the smoke that the broiler creates lends a particular flavor to foods. They are widely used to prepare steaks, hamburgers, chicken and fish. Re/lector In construction, underfired broilers share several common ele• ments. Food is placed on a metal "grid", a heavy duty grill like that of a home barbecue. The grid commonly reaches tempera• tures of over 320°C (600°F) and conducts a significant amount FIGURE 4-4 Diagram of the "radiant" style of of heat to the food. Below the grid, gas broilers have a set of underfired charbroiler. The metal atmospheric burners spaced every four to twelve inches along radiant replaces the usual layer of rock or ceramic briquettes above the broiler's width. The flames are diffused by a bed of rock, the burners. ceramic briquettes, or a metal shield ("radiant") just above the Photo: Vulcan -Hart Company burners. This diffusing layer between the flame and the food

Technology Re\iew of Commercial Foodservice Equipment Volume II, Page 4-3 converts some of the flame's energy to radiant heat. Electric charbroilers may have elements interleaved with the bars of the grid, or the elements may be sheathed inside the grid itself, in which case heat transfer is almost entirely by conduction. As o food cooks on an underfired broiler, drippings burn on hot ele• ments, coals or radiants to create the charbroiler's characteristic flame and smoke. Unincinerated drippings are collected in a grease tray.

The charbroiler's smoke and flame are both a selling point to patrons and an issue of concern for operators. Charbroilers re• quire significant venting, and in some areas the effluent from char broiling is a focus for air quality regulations. Design of the grid may affect smoke and flare up. Several manufacturers pro• duce a grid made of bars that, in cross section, resemble a check mark: V. Each bar is said to act like a small gutter for grease, carrying it away from the flames and directing it towards the grease pan. Grease may also be diverted by tilting the grid. Several broilers have a grid that is slanted toward the cook, or is adjustable be• tween flat and tilted positions. This provides different cooking temperatures from front to back of the broiler as it promotes grease runoff. One manufacturer uses a fan to blow air across the bed of ceramic coals and reduce flare up. and several more use water-filled grease pans. Design of the heat source may also influence smoke and flare up. Gas charbroilers have traditionally diffused the burner's flames with a uniform layer of rock or ceramic coals that con• FIGURE 4-5 vert some of the flame's heat into radiant heat. A metal radiant Overfired upright broiler with two broiling decks. The grids slide out for directly over the burner and a reflector under it may allow more loading and unloading and can be of the drippings to fall into the grease pan without burning, and raised towards the infrared burners shield the grease pan from the heat of the flame. This design has in the top of the cavity or lowered for slower cooking. Two knobs on the the additional benefit of eliminating the need to replace rock or left of the cavity control input to the coals periodically, as well as faster preheat time. burners. Photo: Vulcan-Hart Company Griddle manufacturers have recently begun offering griddles with grooved plates as an alternative to charbroilers. These griddles sear food with the stripes characteristic of a broiler but create no flame, produce far less smoke and use energy more efficiently than a broiler does; additionally, they radiate less heat into the kitchen and require less ventilation.

Technology Review of Commercial Foodservice Equipment Volume II. Page 4-4 TABLE 4-1 Typical grid dimensions, input rates and input densities for underfired and overfired broilers. A 60 kBtu/h cheesemelter may be1,830 mm (6') wide, while a 60 kBtu/h salamander is 600 mm (2') wide; input density reflects this difference as the amount of input energy each can direct to a square meter (foot) of grid surface.

Type of Broiler Fuel Grid Depth Grid Width Input Input Density inches inches kBtu/h kBtu/h sq.ft Underfired gas 14-35 13-122 30-240 16.7-28.8 electric 18 18-30 21-46 3.0-6.6 Upright gas 24-30 24-28 65-100 15.3-20.4 electric 23 26 41 5.9 Salamander gas 12-14 21-28 30-66 12.0-19.6 electric 13-14 25 17-20 2.5 - 2.9 Cheesemelter gas 13-15 24-70 18-60 7.8-10.1 electric 13 20-42 8-16 1.2-2.4

4.4.2 Overfired Broilers Overfired broilers differ according to their typical uses and en• ergy inputs. The highest input overfired broilers may be used to broil inch-thick steaks in volume, while those with lowest input are designed specifically to warm food, melt cheese toppings and finish some dishes by browning the top. All overfired broil• ers cook with a heat source that is positioned above the food, but there are three generally recognized categories delineated by the broiler's input rating and physical configuration. Upright broilers are high-input and generally freestanding. Cheese• melters are low-input broilers that may be countertop, wall mounted or installed above a rangetop. Salamander broilers span the input range between cheesemelters and uprights, and are usually mounted at eye level above a rangetop. As is apparent from Table 4-1, there is some overlap in the typi• cal input ranges for the three categories of overfired broilers discussed below. In addition, manufacturers and operators may use several different terms to refer to the same category: "upright" broilers are also known as hotel broilers and floor broilers; "salamanders" are also called backshelf broilers. Despite their differences, the three types of overfired broilers follow a similar plan. Food is cooked in a broiler cavity that re• sembles an oven without a door. The heat source may be gas radiants, infrared burners or electric elements mounted in the top of the cavity. Food is placed on top of a grid which can usually be adjusted to vary the distance between food and heat source. Cooking is accomplished by radiant heat from above the food and heat conducted from the grid to the food. Controls are simple, usually one or two knobs to adjust banks of elements or burners; like charbroilers, overfired broilers are not thermostat

Technology Review of Commercial Foodservice Equipment Volume II, Page 4-5 controlled. Below the food there is a grease pan to catch drip• pings. An overfired broiler typically has a lighter-weight grid than a charbroiler, and the grid is shielded from the elements or burn• ers when it is covered with food. The grid may not receive and retain as much heat from the burners as a charbroiler grid does, making conductive heating less significant in an overfired broiler. Radiant heat is generated with electric elements, gas infrared FIGURE 4-6 burners or gas radiants. Some manufacturers use powered burn• A salamander broiler, mounted on a backshelf (as above a range.) Like ers that force premixed gas and air through a ceramic infrared the upright broiler, this salamander burner. The high heat generated by ceramic infrared burners can cook a variety of foods including may incinerate some of the smoke and grease that is formed thick cuts of meat. The rack is slightly less adjustable, and the cavity is not during broiling and grease does not drip onto hot coals or radi• as deep as an upright's. ants, thus overfired broilers produce less smoke than underfired Photo: Garland broilers. Upright Broilers. Upright broilers are heavy duty freestanding overfired broilers. Their high input is in the same range as that of a charbroiler, and they can be used to prepare foods like steak and chicken quickly and in large quantities. They have the high• est input rate and production capacity among overfired broilers. Manufacturers commonly offer two identical broiler cavities or "decks" stacked vertically as one unit Ovens may also be stacked with an upright broiler. Some manufacturers mount a finishing oven above an upright broiler so that the heat source at the top of the broiler cavity doubles as a heat source in the bot• tom of the oven cavity. Uprights are constructed for heavy use. The grid is usually counterbalanced so that it can be easily raised and lowered to adjust cooking temperature. It may also pull out on slides against safety stops for loading and unloading. Uprights usually stand on a cabinet style base, and some "modular" uprights can FIGURE 4-7 be placed on a stand or a countertop. A cheesmelter. Note the simple grill, which is not adjustable, and the lack of a Salamanders. Salamanders are medium duty overfired broil• grease pan. ers. Their input range slightly overlaps that of both uprights and Photo: U.S. Range cheesemelters, but they are designed to fit above a rangetop on a backshelf. The broiling cavity is as wide as an upright's but not as deep, typically 300 mm (12") deep instead of 600 mm (24"). Salamanders generally have a lower input rate to match their smaller size, and deliver slightly less energy to each square foot of the grid. They are intended to prepare the same range of foods as a high input upright broiler but at lower volume and without occupying floor or counter space.

Technology Review of Commercial Foodservice Equipment Volume II, Page 4-6 In construction the salamander closely resembles the upright broiler, but is often of lighter weight construction and materials. The grid is not as heavy, although it is usually counterbalanced o and capable of sliding out for loading. Although salamanders are generally defined as medium input broilers mounted on the backshelf of a range, some manufacturers advertise salamanders that can also be wall mounted or set on a countertop. Cheesemelters. Cheesemelters have the lowest input among overfired broilers, and are generally used to melt the cheese on top of foods such as Mexican and Italian dishes, pie and french onion soup. They are usually incapable of fully cooking food items like steak and chicken, and do not have grease pans to catch fat and drippings. In appearance they resemble salaman• ders, although they are generally smaller and of more light• weight construction. This type of broiler is intended for a lim• FIGURE 4- 8 ited set of tasks, and so the grill adjustment is usually not as so• A restaurant range often incorporates a salamander broiler on the back• phisticated as it is for other overfired broilers. The grid is a thin shelf above the rangetop. This model grill which may not adjust to as many positions as a salaman• also takes advantage of the burners der's; in some cheesemelters it fixed. It is not usually counter• below the griddle to include a cheesemelter with a rack that slides balanced or mounted on slides, and typically does not have an out for loading, convenient for use as external handle. a warmer or holding area for food prepared on the griddle. Cheesemelters may be mounted on a wall, a counter or on a Photo: Vulcan-Hart Company backshelf like a salamander. Some cheesemelters are designed with the cavity open both front and back for use as a heated pass-through shelf. Some charbroilers include a cheesemelter underneath their burners to make use of heat radiated down• wards by the briquettes or rocks; cheesemelters may be incorpo• rated in a similar fashion under the burners of a griddle in a MS! ar restaurant range [Figure 4- 8]. 4.4.3 Conveyor Broilers Conveyor or "chain" broilers employ both an overfired and an tfC underfired heat source, cooking both sides of the food product at once. These broilers are ideally suited to broiling hamburger patties in large quantities. Model sizes range from small table- FIGURE 4-9 top broilers favored by convenience stores to large capacity Side view of a conveyor broilers for fast food operations. Conveyor broilers are available broiler with two chains, one with an additional section specifically for toasting buns. Multi• for meats and one for buns. Diagram: Nieco Corporation ple-chain models are available so that more than one size patty or meat product such as chicken, steaks or hamburgers can cook at the same time. Instead of a chain, some models use a teflon belt; this requires an optional "marking platen" to sear broiling stripes onto the food product. Both gas and electric models are manufactured.

Technolog\ Review of Commercial Foodservice Equipment Volume II, Page 4-7 4.4.4 Broiler/Griddle Combination Hybrids Like conveyor broilers, combination broiler/griddles function as two-sided cookers. The unique Clamshell® broiler features a 600 mm (24") wide stainless steel infrared broiler hood mounted on the left end of a griddle. This combination allows the operator to simultaneously grill, poach, broil, and saute a variety of foods, ranging from breakfast menus to dinner en• trees: lobster, oysters, shrimp, sandwiches, egg dishes, steaks, chops, and hamburgers. Both gas and electric units are available in floor and countertop FIGURE 4-10 models. In addition to the flat griddle plate, the manufacturer Electric conveyor broiler. This model also offers a grooved griddle plate and a combination has three chains, each with inde• pendent temperature controls. grooved/flat plate. Photo: Nieco Corporation The gas broiler hood has a single infrared burner rated at 35 kBtu/h and covers approximately four square feet. This model has a "marking grid", a thin grill that makes contact with and sears broiler stripes onto the food product. The electric ver• sion is similar to the gas model but uses quartz halogen tubes as a source of infrared heat. Lowering the broiler hood activates the burners automatically. When the hood is lowered, it is "full" on. No preheat time is required. When the hood is in the raised position, the burner is off. In the lowered position, there is a 76 mm (3") gap between the broiler hood and the griddle surface,

4.5 BROILER PERFORMANCE Since broilers are not thermostatically controlled and manufac• turers have established input rates based on peak production (i.e., high broiling temperatures that minimize cook time), they typically consume energy throughout the day at a rate that is close to their maximum input (e.g. 90% duty cycle.) The end of a cooking event does not automatically return the broiler to an "idle" state, unlike other appliances which consume less energy FIGURE 4-11 to maintain a set temperature once their food load is removed. Gas combination griddle-broiler. This Furthermore, a charbroiler's flame does not remind the chef to model has a grooved griddle plate and a marking grid; both sides of the turn the broiler off between loads because it is partially con• food product will be seared with cealed beneath the grid and/or coals. Thus a cooking energy ef• broiler stripes. Two sided griddles like this one cook twice as quickly as ficiency measured over the timespan of the cooking event has standard griddles, and use energy less meaning for broilers than for other cooking appliances. more efficiently than griddles or broil• However, measured discrete-load cooking energy efficiencies ers. Photo Lang Mfg. Co. provide a benchmark as efforts are made to improve the energy performance of broilers.

Technolog} Review of Commercial Foodservice Equipment Volume II, Page 4-8 4.5.1 Energy Efficiency PG&E has developed a test method for the performance of un• derfired broilers that has been adopted as an official ASTM Test Method. ] However, there are no published data from this re• cent research activity; the cooking-energy efficiencies for un• derfired and overfired broilers reported are based on the 1983 University of Minnesota Comparative Gas/Electric Food Serv• ice Equipment Energy Consumption Ratio Study. ]

Table 4-2 Broiler Cooking Energy Efficiency. Gas Electric

Cooking Energy 15-30 35-65 Efficiency (%)

These cooking-efficiencies were determined by cooking discrete loads of hamburger patties. However, the real-kitchen cooking energy efficiency drops dramatically as the energy consumed by the broiler during "idle" periods is factored into the denomina• tor of the energy efficiency equation. For example, a gas underfired broiler used to cook 45 kg (100 lb) of food over an 8 hour period could consume 600 kBtu (ref. PG&E technical report on the Wolf Commander Char- Broiler: Appliance Performance in Production)[3]. Estimating that 300 Btu was required to cook each kg (lb) of food,'2] the total energy input to the food product over the eight hour period would be only 30 kBtu. This translates to a real-world cooking energy efficiency of only 5%, significantly less than the 15 - 20% efficiencies reported for discrete-load tests (Table 4-2). Restated, only 5% of the energy consumed by an underfired broiler in an actual kitchen is delivered to the food product. The potential for energy-efficiency performance improvements in the design and usage of broilers is obvious.

4.5.2 Energy Consumption Projected energy consumption for gas and electric broilers are presented in Table 4-3 and 4-4. Based on PG&E's in-kitchen monitoring at its production test kitchen, average energy con• sumption rates for underfired gas and electric broilers reflect duty cycles of 90% and 82%, respectively.[3-6] An appliance's duty cycle can be defined as the average rate of energy con• sumption expressed as a percentage of the rated energy input or the peak rate at which an appliance can use energy. Daily en-

Technology Review of Commercial Foodservice Equipment Volume II, Page 4-9 ergy consumption for broilers were calculated by multiplying the median rated input for each broiler category by the respec• tive duty cycle and the hours of operation. Projected annualen- ergy consumptions were determined by assuming 6 day opera• o tions for 52 weeks.

4.5.3 Ventilation Requirements The ventilation requirements for underfired broilers are greater than for other categories of cooking equipment, with the excep• tion of woks and solid-fueled appliances. For example, typical ventilation rates for gas charbroilers operating under wall- mounted canopy hoods are in the range of 540-700 L/s per lin• ear foot (350-450 cfm) of hood. At this time, there are no pub• lished data that quantifies any differences in the ventilation re• quirements between gas and electric charbroilers. However, the strong thermal plume generated by an underfired gas charbroiler suggests that higher ventilation rates may be required.

TABLE 4-3 Projected Energy Consumption for Gas Broilers

Nominal Rated Duty Avg. Energy Typical Annual Energy Size Energy Input Cycle Consumption Op. Hrs Consumption

b (kBtu/h) (%) (kBtu/h) (h/d)a (kBtu) UNDERFIRED:

Charbroiler 3 ft. 90-120 (Median) 105 80c 84 8 210,000

OVERFIRED:

Upright 3 ft. 80-110d Salamander 3 ft. 28-49 Cheesemelter 3 ft. 20-39 (Median) 65e 70' 46 8 115,000

"Operating hours or appliance "on time" is the total period of time that an appliance is operated from the time it is turned "on" to the time it is turned "off. bThe annual energy consumption calculation is based on the average energy consumption rate x the typical operating hours x 6 days per week x 52 weeks per year. The average energy consumption rate and typical hours of operation are based on data from monitoring two 3-ft gas charbroilers in a real-world food service operation.'3'6' An associated duty cycle of 90% was calculated . Typical range for single-deck overfired broiler. The median energy input rate for overfired broilers is based on the ranges for upright broilers, salamanders and cheesemelters. fA 90% duty cycle has been assumed for overfired broilers based on the assumption that the usage pattern is similar to under-fired (e.g., charcoal) broiler operations. Also, typical operating hours were assumed to be the same for both appliance types. The average energy consumption rate was calculated based on the assumed 90% duty cycle and a median energy input rate of 65 kBtu h.

Technology Re\iew of Commercial Foodservice EquipmentVolume II, Page 4-10 The radiant heat gain to the kitchen from broilers contributes significantly to the cooling load of a kitchen. The radiant factor for underfired broilers has been reported as high as 36% and as such, can represent several tons of cooling for a 900 mm or o 1220 mm (3 or 4 ft) charbroiler.17'

4.6 RESEARCH NEEDS The high rate of energy consumption and associated low energy efficiency for gas broilers suggests that research and develop• ment efforts could quickly benefit the food service industry. Broiler control strategies that modulate energy consumption in response to food loading need to be developed and promoted. Instant on/instant off broilers could become the broiler of the future. There is a clear need to better characterize of the per• formance advantages of infrared and quartz halogen heating technologies (both for overfired and underfired).

TABLE 4-4 Projected Energy Consumption for Electric Broilers

Nominal Rated Duty Avg. Energy Typical Annual Energy Size Energy Input Cycle Consumption Op. Hrs Consumption

a b c (kW) (%)

Charbroiler 3 ft. 10-12 6-14 (Median) 11 70d 8 10 24,900 85,200

OVERFIRED:

Upright 3 ft. 11-17e Salamander 3 ft. 5-12 Cheesemelter 3 ft. 2-6 (Median) 10f 709 7 10 21,800 74,500

'Operating hours or appliance "on time" is the total period of time that an appliance is operated from the time it is turned "on" to the time it is turned "off'. The annual energy consumption calculation is based on the a\erage energy consumption rate x the typical operating hours x 6 days per week x 52 weeks per y ear. ""Conversion Factor: 1 kW = 3.413 kBtu/h. The average energy consumption rate and typical hours of operation are based on data from monitoring two 3-ft electric charbroilers in a real-world food service operation. An associated duty cycle of 82% was calculated . Typical range for single-deck overfired broiler. rThe median energy input rate for overfired broilers is based on the ranges for upright broilers, salamanders and cheesemelters, -An 82% duty cycle has been assumed for overfired broilers based on the assumption that the usage pattern is similar to under-fired (e.g.. charcoal) broiler operations. Also, typical operating hours were assumed to be the same for both appliance types. The average energy consumption rate was calculated based on the assumed 82% duty cycle and a median energy input rate of 10 kW.

Technology Review of Commercial Foodservice EquipmenlVolume II. Page 4-11 Other research issues or needs include; • Development of lower emission broilers including a better understanding of time-temperature effects on emissions. • Determination of ventilation differences between gas and electric broilers. • Development of integrated hoods operating at lower exhaust air flows, reduced kitchen heat gain and potential integrated emission control (e.g., catalysts). • Further development of automated, conveyor broilers. One manufacturer has recently introduced a "belt" conveyor electric model. • Development of a standard test method for the performance of overfired broilers (currently on PG&E's research plan). Evaluation of the "Broil-master'" energy saving device in a case study context.

4.7 GAS INDUSTRY MARKET FOCUS Broilers represent a good load-building appliance to gas utili• ties. In gas service territories, the electric broiler does not pres• ent a competitive advantage over gas equipment. However, the intense energy requirements of gas broilers and their potential (real or perceived) to contribute to urban air pollution could be considered a market threat. Conversely, the even more severe fuel costs and emissions from solid-fuel charbroilers present a marketing opportunity for gas broilers. In air-quality sensitive cities (e.g., Los Angeles), the future for solid fueled appliances does not look good. Over the short term, a gas broilers and ro- tisseries may represent a viable option to solid-fueled equipment (This is the strategy being adopted by The Keg and Swiss Cha• let). However, the long-term viability of gas-fired broilers may be dependent on the design of more environmentally friendly equipment. There is a clear need for gas utilities to promote energy efficient broiler technologies to keep high operating costs from impact• ing negatively on the economic viability of a customer. In this vein, the gas industry needs to support development of broiler designs that are more environmentally friendly. With improved design, controls and operation, broilers could in fact, be more energy efficient than alternative appliances. Griddles, for ex• ample, will always have significant stand-by energy require• ments.

Technology Review of Commercial Foodservice EquipmentVolume II. Page 4-12 4.8 REFERENCES 1. PG&E, Food Service Technology Center. Zabrowski. D. Standard Test Method for the Performance of Underfired Broilers. 2. Snyder, O. P., D. R. Thompson, J. F. Norwig. 1983. Com• parative Gas/Electric Food Service Equipment Energy Con• sumption Ratio Study. Final research report prepared by the University of Minnesota under contract with the American Gas Association, 3. PG&E, Food Service Technology Center. Geiger, T. Wolf Commander Range-Match SUPER Char-Broiler: Appliance Performance in Production. 1993. Final Report. Report No, 008.1-91-28. 4. PG&E, Food Service Technology Center. Zabrowski, D, Wells Model B-50 Electric Broiler: Appliance Performance in Production. 1994. Final Report. Report No. 5011.94.3. 5. PG&E. Food Service Technology Center. Selden, M. Appli• ance Performance in Production: "Hobart" Electric Char Broiler Model CBS J. 1992. Final Report. Report No. 008.1- 92-4. 6. PG&E, Food Service Technology Center. Cooking Appli• ance Performance Report: Production Test Kitchen. 1990, Final Report. Report No. 008.1-90.8. 7. American Society of Heating, Refrigerating and Air- Conditioning Engineers, Inc. 1993 ASHRAE Handbook: Fundamentals; 1-P edition. 1993.

Technology Review of Commercial Foodservice EquipmentVolume II, Page 4-13 5. RANGE o 5.1 INTRODUCTION The most familiar piece of equipment in restaurant kitchens is the range. Topped with several gas burners or electric elements, typically incorporating a standard oven, the ranges used in food- service operations are much like those installed in most homes. The major difference is durability: a food service range must withstand constant use and abuse while preparing tens or hun• dreds of meals a day. The top section of the range, which consists of burners or ele• ments used for cooking with pots and pans, is referred to as the "range top". Range tops, specifically the gas burners and electric elements that make them up, are discussed in this section of the report. The oven that is typically built into a range is called a "range oven". Range ovens are most often standard ovens sized to fit under the range top, though a growing number of manufac• turers offer convection or combination range ovens. Ovens are discussed in detail in Section 7 of this report. Ranges may also FIGURE 5-1 include griddles and broilers; these appliances are detailed in Six-burner range on oven base. Section 3 and 4, respectively. ~>hoto: Southbend, A Middleby Company The configuration of a range is flexible by definition. The space J underneath a range top, usually devoted to a range oven, may also house a refrigerated cabinet or storage space for pots and pans. Above and behind the range top is the backshelf, which often houses a salamander- or cheesemelter-type broiler. Smaller ranges can include a narrow griddle and/or charbroiler on either side of the range top. Larger ranges consist of full- sized appliances joined side-by-side to the range top in a bat• tery, with matching trim, countertop sections and possibly a front-mounted gas manifold; such a range battery may stretch the length of a kitchen wall. Ranges are often divided into three categories depending on their intended use: Heavy duty or hotel ranges, medium duty or restaurant ranges, and specialty ranges such as stockpot and taco ranges. Heavy duty ranges are built for continuous use in high- volume operations such as hospitals, schools and large restau• rants. They feature appliances with high energy inputs and sturdy construction, with range tops built to support the weight of large stockpots and powerful enough to heat such a vessel quickly. Restaurant ranges are more suited to a smaller opera• tion, such as a lunch counter or smaller restaurant. Medium duty ranges, although substantially built, are not as well suited for

Technology Review of Commercial Foodservice Equipment Volume II, Page 5-1 heavy use or abuse, and often have lower energy inputs (e.g., range top burners of 15-20 kBtu/h instead of a hotel range's 20- 30 kBtu/h). Specialty ranges are built to perform one function, as the name implies. Taco ranges are configured to hold and heat food in GI pans. Chinese ranges, treated separately in Section 6, are de• signed for wok cooking. Stockpot ranges have one or two gas open burners and a very heavy duty cast iron grate, and are in• tended to cook large quantities of food in one cooking vessel. Range tops vary with fuel source and with heating technology. Both gas burners and electric elements are built into restaurant range tops, although gas is by far the most common. In hotel range tops, gas is almost universal.

5.2 COOKING PROCESS All range tops provide heat to a pot or pan from below. The method of heat delivery to the pot may vary, but the cooking process is always a function of the interface between the inside of the hot pot and the food. One way in which the range top may affect this interface is through even heating. Some range top heating strategies provide uniform heat to the bottom of the pot, while others concentrate it more in one area. This becomes a significant performance factor if the range top is used in a process such as cooking pancakes, where surface uniformity is important; however, the choice of pan construction can be used to mitigate unevenness in the heat source,

5.3 CONTROLS Range tops are generally not amenable to timers or cooking computers, and most range top cooking demands the attention of the chef. Controls on the range top are typically simple. There is most often an infinite-control knob to regulate the input of each burner or element. The controls are calibrated in terms of the percentage of input, as the burner does not generally sense the temperature of the pot. An exception to this rule is a temperature-limiting switch included in advanced range top technologies, to guard against the pot-melting temperatures that these range tops can produce. Controls which are specific to new technology are discussed in the Heating Technologies sec• tion of this report.

Technology Review of Commercial Foodservice Equipment Volume II, Page 5-2 5.4 HEATING TECHNOLOGIES Gas burners and electric elements can be described as "open" or "closed". The most common type of range top uses open burn• ers, applying flame directly to the bottom of the pot. Open tops generally offer fast heatup and slow cleanup: spills can fall di• rectly onto the burner, and cleanup may mean moving or remov• ing parts of the range top. A closed burner or element would seal the heat source under a ceramic, glass or metal cover, pre• senting a smooth surface to the bottom of the cooking vessel. This is desirable to the chef because it is very easy to clean the range top, and also easy to slide pots and pans on and off of the hot spots. Each heating technology described here comprises a different type of burner or element. Manufacturers commonly allow the user to specify a combination of burner or element types.

5.4.1 Open Burners and Discrete Elements 5.4.1.1 Open Gas Burners. Open gas burners remain the burner of choice for most chefs. They are inherently sturdy, in• expensive to manufacture, and they respond instantly when the burner is turned on and adjusted. The visible flame provides di• rect feedback on the heat to the pot, enhancing the chefs con• trol, and can ignite spattered grease to "flash" flame into the pan during display cooking. The gas burner is typically a hollow ring of cast iron or steel with holes that jet gas upwards towards the cooking vessel. A newer but similar design is the star burner, which has arms ra• diating from a central hub, and spreads its flame more evenly over the pot bottom. The gas is mixed with some primary air at an air shutter on the manifold. Secondary air provides most of the oxygen for combustion, combining with the gas as it jets from the burner. The flame is controlled with a gas valve mounted on the front of the range. The burner is set into the surface of the range top and covered by a metal grate which supports the cooking vessel. Grates are designed so that pots can be slid easily from burner to burner, and so that a pot in any position will be stable. There may be a spill tray underneath the burner to catch falling food. The grates may be removable, and on some range top the burner heads lift off for easy cleaning. The standard input rating for open gas burners has historically been 20 kBtu/h. Chefs would commonly drill larger holes in the burner to increase the output; this allowed for more flame and

Technology Review of Commercial Foodservice Equipment Volume II, Page 5-3 flare during display cooking. Manufacturers have recently re• sponded with certified 30kBtu/h burners, which are becoming the standard on heavy duty ranges. Studies at PG&E indicate that these higher input burners do not use more energy to cook: although the gas input is higher, the cooktime is correspond• ingly shorter. However, the net effect of these more powerful burners will almost certainly be an increase in energy consump• tion, since burners are often left on between cooking events, and sometimes for the entire meal period. 5.4.1.2. Electric Speed Coils. Sheathed electric coils, wound into a spiral element, are used on light and medium duty restau• rant ranges. These elements are also known as "speed coils." Analogous to the elements on a residential electric range, they provide fast heat and response. They are relatively fragile though, and not recommended for use with heavy stock pots, 5.4.1.3 Electric French Plates. Also called round plates. In a French plate element, the open electric coil is covered with a solid metal disk. They are generally 150-250 mm (6-10 inches) in diameter, and protrude 6 to 12 mm (1/4 to 1/2 inch) above the range top. By concentrating heat under the pot, they preheat faster than an electric hot top, and are more durable and easy to clean than an electric speed coil.

5.4.2 Closed Burners and Elements 5.4.2.1 Gas Hot Tops. The hot top is a flat metal plate made of cast iron or steel, heated from underneath by atmospheric gas burners. The bottom of the plate may be textured or finned to distribute heat evenly. The surface of the hot top reaches tem• peratures of 425°C to 540°C (800-1000°F) at maximum input. Some hot tops are constructed so that there is a temperature gradient from front to back, allowing different styles of cooking on the same section. The hot top section is typically 600 mm (24") deep and 300-450 mm (12-18") inches wide. A range top may consist of several sections. Each typically has its own burner and control. Hot tops allow the entire surface of the range top to be used in• stead of only the space over the burners. This allows an opera• tion that prepares many small orders at once to fit more pans on the range top. Pots slide across the flat surface more easily than across the grids on an open burner range top. This facilitates moving items such as sauces and soups from a front hot top section at a higher temperature setting (e.g., boiling) to the other hot top sections set at lower temperature settings for continued simmering or holding. However, the hot top is slow to heat: it

Technology Review of Commercial Foodservice Equipment Volume II, Page 5-4 may take 30 to 60 minutes before the plate reaches its maximum temperature. It is similarly slow to respond to changes in the control setting. Hot tops are typically preheated once in the morning, and left at maximum input all day. They consume energy at a high rate, and radiate more heat into the kitchen than any other type of range top. Typical input ranges from 20-40 kBtu/h per section. 5.4.2.2 Gas Radial Hot Top. Also called French top or pot ranges. This is a specialized hot top, in which the metal plate is inset with removable concentric rings. These ring sections may be removed to expose more of the cooking vessel to the direct flame of the burners. The burners are high input, up to 45 kBtu/h, arranged in concentric circles beneath the top. The con• trols allow the operator to adjust input to each ring burner sepa• rately, 5.4.2.3 Electric Hot Tops. Electric hot tops are not common. They are identical in construction and detail to the gas hot top, except that their heat source is an electric element clamped to the bottom of the plate. Typical input ranges from 5 kW to 7.5 kW per section.

5.5 ADVANCED TECHNOLOGIES Technologies developed for commercial use have focused on improving gas burner efficiencies, and on designing easy-to- clean closed range tops for both gas and electric ranges,

5.5.1 Power Burners Power burners premix gas and air in stoichiometric proportions for efficient burning. Because no secondary air needs to be drawn into the flame at the burner head, the grate can be con• structed to form an almost airtight chamber beneath the pot. This eliminates the rapid convection that washes much of a conventional burner's heat up and around the cooking vessel. Thus more of the hot combustion products can transfer their heat to the bottom of the vessel. The intense heat of the power burner has presented its own obstacle. The initial commercial release was halted because users complained that they were warping pots on the new burners, apparently underestimating the speed and letting their cooking vessels boil dry. Testing by the American Gas Association Laboratories (AGAL) showed a power burner to be 36% faster and use 34% less en• ergy than a conventional 20 kBtu/h star burner. Although the initial cost is higher than a standard burner; AGAL estimated

Technology Review of Commercial Foodservice Equipment Volume II, Page 5-5 that energy savings with a power burner range top would pay back the cost difference in under two years.' '

5.5.2 Sealed Combustion CGRI has developed a prototype range top which features stan• dard gas burners under a glass ceramic surface. Each burner is surrounded by a ceramic cup which is heated to over 650°C (1200°F) during operation. Heat is supplied to the cooking ves• sel by conduction through the glass ceramic surface and by ra• diation from the burner flame and ceramic enclosure. An over limit switch shuts the bumers off if the temperature of the ce• ramic glass top rises outside the operating range. The burners are completely enclosed, and all combustion prod• ucts are vented outdoors. This closed burner design has the ap• peal of easy cleanup, a visible heat source and according to CGRI a higher efficiency than standard open gas burners. The current sealed combustion prototype is for residential appli• cations. The unit's easy cleanup, speed and lower heat gain to the kitchen would also be valuable in a food service setting. Gaz de France, as part of their strategy to help the food service industry, and in concert with commercial cooking equipment manufacturers, have introduced a patented Vitrogaz ceramic hot plate. It features a smooth, flat, easy to clean cooking surface and is powered with two high performance, 27 kBtu/h radiant burners. It can be used with an open flame or as a solid-top plate. Plate temperatures are adjustable between 60°C and 600°C(140oFandlll2°F).141

5.5.3 Infrared Burners Infrared burners force gas and air through a ceramic burner. The surface of the burner, where combustion takes place, is perfo• rated with thousands of pores. During operation the ceramic burner face reaches temperatures above 870°C (1600°F). Infra• red burners are more efficient than the standard gas burner, but they have not yet been successfully applied to the commercial food service range top. One problem has been soiling the burner with spilled food. A solution is the infrared jet impingement burner, which uses an infrared ceramic burner beneath a perforated glass-ceramic plate. The glowing ceramic burner transmits radiant heat to the cookpot, and the combustion products are propelled through the holes in the ceramic glass shield to impinge on the bottom of the pot. The shield prevents most spillage from dripping onto the

Technology Review of Commercial Foodservice Equipment Volume II, Page 5-6 burner, and what does flow through the holes is incinerated. The developer, Tecogen Inc., rates ease of cleaning the bumers as "somewhat better than conventional burners." The developer reports a water boil efficiency of 66% as opposed to 45% with a regular burner.1 ]

5.5.4 Induction Range Tops Induction is an electric heating technology that solves the prob• lem of slow-response electric elements and hot tops. Induction heating is very fast, easy to control, and offers easy cleanup with a sealed cooking surface. It is also inherently efficient. Tests at PG&E indicate that up to 80% of the energy supplied to the induction coil is transferred to the cooking container and food product. ' Induction range tops use an induction coil located beneath a ce• ramic cook top. As electric current flows through the coil, a cor• responding field develops above the surface of the ceramic cook top. The field itself is not hot, and doesn't heat the ceramic: a hand placed on the range top will not be burned or heated. But the bottom of a metal pan set on the ceramic surface intersects the field, which induces a current in the pan. This current heats the pan bottom rapidly, and the bottom becomes in effect an electric element, Because the field can only do work on the metal (magnetic) pot, removing the pot automatically turns down the energy input to the appliance. Full input is restored instantly when a pot is placed on the ceramic cooktop. While idling without a pot on the range top, the induction element draws a small fraction of its full input energy, and adds no heat to the kitchen. Heating can be controlled by changing the energy input to the induction coil. The response to change is rapid, comparable to a gas open burner. Some induction units have electronic controls that allow patterns of heating appropriate to different styles of cooking, e.g. a full-input heating period to raise soup to a boil followed by a reduced input simmer. Induction range tops also include temperature limiting switches, which sense the tempera• ture of the ceramic surface and cut off input when it exceeds safety conditions (e.g., when a pot has boiled dry). Induction range tops have some practical limitations. Currently commercial models exist, but mainly as single-unit hot plates. The coils are expensive and may yet prove too fragile for heavy- duty food service applications. Finally, the induction range top will only heat pots that are made of magnetic materials. At pres• ent compatible cookware tends to be expensive, and chefs may

Technology Review of Commercial Foodservice Equipment Volume II, Page 5-7 be reluctant to retool their kitchen for use with this new tech• nology.

5.5.5 Halogen Range Tops Halogen range tops have two of the major advantages of an in• duction range top: fast response to controls and a sealed cooking surface. In addition the halogen elements glow red in proportion to the energy input, providing visual feedback of heat intensity. Unlike induction range tops, the cooking surface does heat up, and power does not instantly modulate to idle when the pot is removed. The heat source for this range top is a set of halogen lamps be• neath a glass ceramic cooktop. Pots and pans rest directly on the ceramic, and are heated by radiant energy from the lamps. An over limit switch monitors the glass ceramic material, cutting off power if the temperature of the cooktop exceeds safe limits. The efficiency of a residential halogen cooktop has been re• ported at 52%-58%.1?1 Currently this technology is not available in commercial range units.

5.5.6 Automatic Burner Shut Off and Re-Ignition. In catering kitchens it is often more practical for the user to leave open flame burners lit when not being used, rather than turning the gas off and re-lighting it each time. Gaz de France, along with Madec-Mater company has patented the Top-Flam- an automatic shut-off and re-ignition device which is triggered by cookware detection. They proclaim energy savings around 50%.i4]

5.6 RANGE TOP PERFORMANCE

5.6.1 Performance Evaluation Criteria ASTM standard F 1521-94 Standard Test Methods for Per• formance of Range Topsm developed at PG&E's Food Service Technology Center provides a means to compare performance and energy use of range tops.[9J These test methods cover the performance of gas and electric range tops including both dis• creet burners and elements and hot tops. The application of the test method provides maximum rate of energy input, tempera• ture uniformity of heating surface, cooking energy efficiency and production capacity. Maximum rate of energy input is a rough index of the "power" of a range top. The test method reports the total energy input

Technology Review of Commercial Foodservice Equipment Volume II, Page 5-8 rate for all the burners on a range top. It is more common in catalogs to see a rating for individual burners or elements. For a given type of burner or element, a higher rate of energy input generally indicates that the burner can supply more heat to the pan. This is only true when comparing similar burners; a high- efficiency burner can use less energy but perform more work than a low-efficiency burner (i.e., cook the same quantity of food in less time). The heat transfer characteristics of a cooking unit can be simu• lated by measuring the temperature uniformity of a steel plate simulating the bottom of a frying pan. Temperature uniformity gives the temperature at several points across the area of a pot's bottom, indicating hot or cold spots. Production capacity is the amount of food that a burner or ele• ment can cook in a given time, expressed as gallons of water that can be raised from 21-93°C (70-200°F) in one hour. This gives an indication of the "speed" of a burner.

5.7 BENCHMARK ENERGY EFFICIENCY Cooking efficiency as defined by the ASTM Standard Method of Test for Range Tops'8' is the ratio of the amount of energy going into the food versus the amount of energy supplied to the burner:

CookingEfficiency = x 100% fc.Appllimcc Energy efficiency is determined by heating water from 21 to 93°C (70 to 200°F) at both the half-and full-energy input rates. Using PG&E data from applying this method of test to different range-top types'9', along with data from the Minnesota study and range top development and testing by AGAL[n], bench• mark energy efficiencies are presented in Table 5-1. The efficiency of gas range tops have received attention from both the manufacturer and the end user.113' Research organiza• tions such as the GRI have been instrumental in attempting to develop and bring high efficiency gas models to the US market. Standard electric range tops, at roughly 65-75%, are already quite efficient. With the introduction of induction technology, electric range top efficiencies are approaching 85%.

Technology Review of Commercial Foodservice Equipment Volume 11. Page 5-9 TABLE 5-1 Range Top Energy Efficiency6 High Efficiency Standard Gas (% Electric. (%) Gas (%)

45 - 60 25 - 30 65 - 85

' Energy efficiency numbers for range tops are best estimates based on PG&E test data from applying ASTM Standard Test Methods to four different range tops, on preliminary results from revising the existing ASTM Standard and applying it to three electric induction units and on data from both the Minnesota Study and AGAL test- ing.""1

5.8 RANGE TOP ENERGY CONSUMPTION Projected energy consumption for gas and electric range tops are presented in Table 5-2 and 5-3. The energy consumption rates for the range tops and range ovens are based on in- kitchen monitoring of two gas and two electric ranges, each outfitted with either a standard or a convection oven, in the PG&E production-test kitchen. " ' The duty cycle was calculated by dividing the daily energy consumption rate by the appliance median energy input rate. Typical operating hours were gleaned from in-kitchen energy-use monitoring experiences and obser• vations as well as on the PREP study' ' and a proprietary end- use monitoring report. Projected annual energy consumption was determined by assuming a 6-day per week, 52-week per year operation.

5.9 VENTILATION REQUIREMENTS Ranges are classified as medium-duty from the perspective of exhaust ventilation. For a side-wall canopy hood, the design ventilation rate for steam equipment would range from 100- 150 L/s (200- 300 cfm) per linear foot of hood.

5.10 RESEARCH NEEDS Gas range tops have historically had several advantages over electric range tops. Gas is fast: there is no wait for preheating. Gas is responsive: an adjustment to the controls changes the heat to the pan bottom immediately. Gas is durable: heavy duty construction and long life are hallmarks of gas range construc• tion.

Technology Review of Commercial Foodservice Equipment Volume II, Page 5-10 TABLE 5-2 Projected Energy Consumption for Gas Ranges Nominal Rated Duty Avg. Energy Operating Annual Energy Size Energy Input Cycle Consumption3 Hours Consumption c (kBtu/h) (%) (kBtu/h) (h/d)° (kBtu)

Range Top 6 Burners 120-210

(Median) 165 20 32 12 120,000

Range Oven 35-45 (Median) 40 40 16 39,900

Total Range 205 48 160,000

'Average energy consumption rates are based on monitoring two gas ranges in a real-world production kitchen.|l4,nj bOperating hours or appliance "on time" is the total period of time that an appliance is operated from the time it is turned "on" to the time it is turned "off. 'The annual energy consumption calculation is based on the average energy consumption rate x the typical operating hours x 6 days per week x 52 weeks per year.

TABLE 5-3 Projected Energy Consumption for Electric Ranges

Nominal Rated Duty Avg. Energy Operating Annual Energy Size Energy Input Cycle Consumption3 Hours Consumption (kW) (%) (kW) (h/d)b (kWh)c (kBtu)*

Range Top 6 Elements 12

(Median) 12 25 12 11,200 38,300

Range Oven 8 (Median) 8 25 4,990 17,000

Total Range 20 16,200 55,300

"Average energy consumption rates are based on monitoring two electric ranges in a real-world production kitchen.1'6'"' bOperating hours or appliance "on time" is the total period of time that an appliance is operated from the time it is turned "on" to the time it is turned "off. The annual energy consumption calculation is based on the average energy consumption rate x the typical operating hours x 6 days per week x 52 weeks per year. Conversion Factor: l" kW = 3.413 kBtu/h.

Technology Review of Commercial Foodservice Equipment Volume II, Page 5-11 Gas is inexpensive: even though it operates at lower efficien• cies, the operating cost for a gas range top is often half of that for an electric range top. In turn, electric range tops have had the advantage of high effi• ciency and easier-to-clean closed burners. The induction range top combines these features with a serious challenge to gas' su• periority in speed and responsiveness. It is an easy to clean, fast heat source with a discrete load cooking efficiency of 80% plus, and it adds little heat to the kitchen. In real world cooking, in• duction saves even more energy by dropping to effectively zero input the instant a pot is removed from the element, and coming back to full input when it is replaced. Although induction range tops have not yet been proven by years of use in the food serv• ice kitchen, and the durability of the element and ceramic cooktop remain to be seen, they represent a credible challenge in a category that has historically been dominated by gas appli• ances. Gas range top improvements have focused on developing sealed elements and higher efficiency. Future research should continue along these paths, with emphasis on the following: • Further development of the sealed combustion range top for commercial food service. This technology would allow ventilation at lower air flows and reduce kitchen heat gain, as well as providing a desirable closed cooktop. • Development of a hot top using infrared burners. This tech• nology is already applied to analogous appliances such as griddles, and would reduce energy costs for gas hot tops. • Development of higher efficiency, low-cost open gas burn• ers. • Investigate the feasibility of the cooking vessel sensor. Open gas burners should take advantage of their traditional strength-instant heat-to turn off when the pot is removed, and on when it is replaced. This can increase the cost advan• tage of gas, and provides a response to one of the strong features of the induction range top: zero idle energy usage. This will also reduce heat gain to the kitchen. Collaboration with Gas de France may be an option. • Development of cooking vessel temperature feedback. An over limit switch to cut input when a pot has heated to the point of warping would allow further marketing of the power burner. If sensitive enough, such a device could begin to automate cooking. For example, a stockpot could be brought to a boil and then held at simmer.

Technology Review of Commercial Foodservice Equipment Volume II, Page 5-12 5.11 GAS MARKETING Focus With the recent focus of North American appliance manufactur• ers on induction cooking (a development strongly supported by electric utilities), it is imperative that the gas industry rethink its strategy with respect to the development of an advanced (high- tech) burner. Although the gas open burner will dominate the market due to low cost and solid performance, it appears that the induction cook top is successfully penetrating upscale and niche market food service operations. From a conservation perspective, gas utilities should promote the use of open burner or partial hot tops over full hot tops. This can significantly reduce operating costs of ranges and heat gain to the kitchen.

5.12 REFERENCES 1. Young, R., Cesio, C, 1995. "Montague Model V136-5 Heavy-Duty 30,000 Btu/h Open Top Gas Range: Applica• tion of ASTM Standard Test Method F 1521-94." PG&E Products and Services Report No.5011.94.61, October. 2. American Gas Association, Food Facilities and Energy News: Advances in Gas Cooking Technology into the 1990s-an educational supplement published 13 times a year and bound into Restaurants and Institutions and Foodserv• ice Equipment & Supplies Specialist magazines under the direction of AGA. 3. Canadian Gas Research Institute, 1992. " Gas Technology Update: Development of a Sealed Combustion Gas Range." Bulletin Number 2, August. 4. Gaz de France, 1992. Gas Utilization Research Centre, Re• search and Development Division CERUG Activities Re• port, pp.24. 5. Gas Research Institute. "Advanced Residential and Light Commercial Cooktop Burner: a GR] Field Test Status Re• port." 6. Based on preliminary results from applying the ASTM Range Top Standard to three induction units. Reports are pending publication. 7. Gas Research Institute, 1995. Project 8. ASTM Standard Test Method for Performance of Range Tops: Designation F 1521-94, 1994. In Annual Book of ASTM Standards, Philadelphia, Vol. 01.04.

Technology Review of Commercial Foodservice Equipment Volume H, Page 5-13 9. Young, R., 1995. "Development and Validation of a Uni• form Testing Procedure for Range Tops". PG&E Report 1 - 22.95.20 prepared for the Research and Development De• partment, October. 10. Snyder, O.P., and J.F. Norwig. March 1983. "Comparative Gas/Electric Food Service Equipment Energy Consumption Ratio Study. University of Minnesota. 11. American Gas Association, 1986. "Performance Evaluation Methods: Convection, Deck, and Range Ovens." Prepared for the Gas Research Institute, GRI-87/0182, December. 12. Himmel, R.L. and Stack, R.E., 1981. "Commercial Cooking Equipment Improvement, Volume I: Range Ovens". Ameri• can Gas Association Laboratories report to the Gas Research Institute, GRI-80/0079.1, October. 13. Little, Arthur D. Inc., August 1993. "Characterization of Commercial Building Appliances": Final Report for Build• ing Equipment Division Office of Building Technologies U.S. Department of Energy, pp. 5-40. 14. PG&E, 1990. "Cooking Appliance Performance Report: PG&E Production-Test Kitchen." PG&E Research and De• velopment Report No. 008.1-90.8, May. 15. Young, R., 1993. "Montague Model V136-5 Heavy-Duty Open Top Gas Range: Appliance Performance in Produc• tion." PG&E Report 5011.93.7 prepared for Products and Services Department, December. 16. Young, R., 1992. "Toastmaster Model RA36C1: Electric Range Performance Report". PG&E Report 008.1-92.10 prepared for Products and Services Department, September. 17. Blessent, J., 1991. "Appliance Performance Report: Vulcan- Hart Electric Range, Model VR-4. PG&E Report 008.1- 90.24, prepared for Research and Development Department, June. 18. Claar, C.N., Mazzucchi, R.P., Heidell, J.A., 1985. The Proj• ect on Restaurant Energy Performance (PREP) - End-Use Monitoring and Analysis, Prepared for the Office of Build• ing Energy Research and Development, DOE, May.

O

Technology Review of Commercial Foodservice Equipment Volume II, Page 5-14 6. CHINESE RANGE/WOK o 6.1 INTRODUCTION Ethnic menus are hot-Chinese, Vietnamese and Thai! As for equipment, the hottest thing—literally—is the Chinese range.111 Chinese ranges are also finding their way into more non- traditional kitchens from family-style restaurants to hotels as the trend towards healthy eating continues. Here, the Chinese range is usually found in the middle of a regular cooking line. Although the majority of Chinese ranges are custom-made, they are generally classified as traditional Oriental units unique to different cooking styles (Guangdong, Shanghai, Chiu Chow and Chop Suey) or North American units which differ in con• struction only-East Coast style and West Coast style. The heat source can be natural gas, propane or butane gas. Natural gas is by far the most common fuel source. A gas valve at knee-level allows the chef to adjust the heat while using both hands to cook. Energy input rates range from 50 kBtu/h to as high as 160 kBtu/h or more, depending on the type of burner. The pur• Figure 6.1 - Heavy-Duty gas pose of the high input rates is to facilitate the short term, high range shown with woks and an temperature cooking process used in the preparation of Orien• enclosed base. tal-menu items. The basic Chinese range is constructed of heavy-gauge steel and averages 760-1150 mm (30-45") in depth and 860-910 mm (34- 36") in work height, often equipped with a high back shelf and rack for woks and utensils.'1' Some ranges are insulated with fiberglass and feature flue risers for ventilation (e.g., East Coast style ranges) or use the flue gases to heat the soup wells (e.g., the Guangdon, Shanghai and Chiu Chow ranges). Units which are not insulated and flueless, feature perforated water lines to flush water across the range top for cooling. A built-in slop trough at the back of the range top allows drainage for the water and any splattered food it has lifted (e.g., West Coast style ranges). Each range has one or more chambers or wells (openings) over which woks are placed for cooking. The overall width of the range is determined by the width required to accommodate the number and diameter of woks and bowls desired, allowing a 152 mm (6") space between them.12' The number, diameter and heat inputs of these chambers are specific to the chefs prefer• ences and cooking style. Woks are available in diameters of 300-800 mm (12- 32"). What's important, however, is the rela• tionship between the wok itself and the chamber. The chamber

Technology Review of Commercial Foodservice Equipment Volume II, Page 6-1 diameter must be 50-100 mm (2-4") smaller than the wok di• ameter in order to ensure a proper wok fit.'"' Traditional type ranges may also include several 300 mm (12") soup pot hold• o ers and open burner sections. Chambers are available in 250 mm, 300 mm, 350 mm, 400 mm, 450 mm, and 500 mm (10", 12", 14", 16", 18" and 20") diameters, increasing in increments of 50 mm (2 inches), and can go up to 760 mm (30 inches). The smaller chamber diame• ters are used for northern-style Hunan, Szechwan and Mandarin cooking; medium-sized chambers are used for southern-style Cantonese cuisine. The large chambers are found in high- production kitchens.l1]

Water spouts, which are used to rinse woks Flue risers, chimney extensions found on between sauteeing, typically are specified one insulated East Coast style ranges, provide for per chamber. ventilation. Uninsulated West Coast ranges use a water line to cool the range top.

Chambers must be 2" to 4" smaller than the wok. Generally, one chamber should be specified for every 25 dining seats. Gutters carry slop into an optional external slop sink equipped with a strainer basket. The serving shell is Some East Coast ranges have such sinks normally 7" to 8" wide. integrally attached, while West Coast ranges On West Coast ranges, il leature troughs that are built in. serves as a covering for the water line that cools the range top.

Gas controls at knee level allow the operator to adjust burner temperature while simultaneously using both hands to cook

The Chinese range is made of heavy-gauge Removable drip pans should be situated steel, averaging 30" to 45" in depth and 34" to beneath each burner. 36" in work height.

Figure 6.2 - East Coast style Chinese range schematic with two chambers, knee-controlled gas lever and flue risers.

Technology Review of Commercial Foodservice Equipment Volume II, Page 6-2 6.2 COOKING PROCESSES The Chinese or wok range is a self-contained range, having one or more "wells" or chambers which is designed to use a wok as i the cooking utensil. The primary cooking method is stir frying. Stir-fried menu items require high cooking temperatures to quickly sear the exterior of the food, locking in the flavours while not destroying natural colour and vitamins. A variety of foods cut into appropriate sizes and shapes, generally thin strips, may be combined in this technique (meat and vegeta• bles, poultry and fish and so on). The food items are added to the hot cooking medium, traditionally peanut oil (used because of its flavour and its high smoking point) and stir fried. That is, the food is kept in constant motion by stirring, lifting and toss• ing for a short amount of time over high heat.[3]

6.3 CONTROLS Although burners usually have modulating gas valves with ad• justable inputs between on and off, they are typically operated at maximum gas input.

6.4 HEATING TECHNOLOGY D 6.4.1 Gas Each wok chamber can be fired by a one-, two- or three-ring burner, depending on its diameter. Ranges designed with up to 450 mm (18") woks require 53 kBtu/h burners; from 500 mm (20") up require 107 kBtu/h burners. Standard models are available with up to as many as 8 to 10 burners. Standard ring- type burners are used in conventional Chinese cooking and can produce between 55 kBtu/h and 110 kBtu/h outputs. Jet burn• ers, rated between 120 kBtu/h and 130 kBtu/h, provide more intense heat and are used in Mandarin cooking. The jet burner is usually placed closer to the wok to create a faster, more in• tense heat and decrease cooking time. Shielded-tip or duck- mouth burners, a variant of the jet burner, deliver the same in• tense heat, but have metal tips that prevent each port from be• coming clogged with food. ^]

6.4.2 Electric There are very few electric woks on the market. Recently, there has been talk of applying induction technology to Chinese ranges.

Technology Review of Commercial Foodservice Equipment Volume H, Page 6-3 6.5 TYPES OF CHINESE RANGES

6.5.1 Traditional Oriental Units 6.5.1.1 Guangdong. The Guangdong range features 450­ 500 mm (18­20") diameter cooking or wok chambers and 300 mm (12") soup chambers which are heated by the flue gases from the rear of the range unit. It is equipped with power < GUANGDONG >' burners rated at 150 kBtu/h per burner. 6.5.1.2 Shanghai. This unit features 450­500 mm (18­22") H • .­ I ■ diameter cooking chambers and 300 mm (12") soup chambers '■ i —r^~ which are also heated by the range's flue gases. This range is equipped with power burners rated at 150 kBtu/h per burner for the woks and with open burners, rated at 40 kBtu/h per burner, located towards the back of the range top. 6.5.1.3 Chiu Chow. The Chiu Chow range, similar to the (SHANGHAI) Shanghai, features 450­500 mm (18­22") diameter cooking chambers and 300 mm (12") soup chambers heated by its flue H gases. This range has power burners for the woks rated at H1 T32T" 150 kBtu/h each. This style of range may also have an open burner with a grate, rated at 40 kBtu/h, towards the back and centered between the two soup chambers. 6.5.1.4 Chop Suey. The Chop Suey range features 400­ 600 mm (16­24") diameter "wok" cooking chambers. This type (CHIU CHOW) of range comes with open or jet burners rated from 80 to 125 kBtu/h per burner. It does not have a flue. A Canadian manufacturer incorporates what it calls a "...new concept in "ffiT" chop Suey range design and engineering..."'41. The burners generate extremely high temperatures (1100°C (2,000°F)) in­ side the chamber, without transferring heat onto the range. The gas chamber is completely isolated. The heat is focused on the wok or pan by flame guide rings, then conducted out of the gas chamber by three separate ventilation systems.l4] I (CHOP SUEY) ■ ­*­, «» 6.5.2 North American Units H • ♦ . ­ 6.5.2.1 East Coast Style. The East Coast style range is insu­

HI lated (front and sides) with fiberglass and features flue risers ! II for ventilation. Some models also offer chambers lined with refractory brick for additional heat protection. Like traditional Figure 6.3 ­ Traditional Oriental­type Oriental range styles, this unit's cooking chambers are 400­600 ranges. mm (16­24") in diameter; the soup chambers are 300 mm (12") in diameter. Energy inputs range from 80 kBtu/h per burner to 125 kBtu/h per burner, depending upon burner configuration­

Technology Review of Commercial Foodservice Equipment Volume II, Page 6­4 open or jet. This range type is also characterized by a rear food trough with an external sink and food strainer. 6.5.2.2 West Coast Style. The West Coast style range has neither insulation nor flues, but features perforated water lines to flush water across the range top for cooling. A built-in trough at the back of the range top allows drainage for the wa• ter. Steel cooking chambers measure from 400-600 mm (16- 24") in diameter. Energy input ranges between 50 and 160 kBtu/h. One manufacturer's unit features a unique well venting system which carries heat away from the kitchen and into a vent opening in the high shelf.

Table 6.1- Summary of Chinese Range Types

Range Type Cooking Chamber Burner Type Input Rate per Chamber Diameter Burner (inch) (kBtu/h) Traditional: Guangdong Wok 18-20 Powered 150 Soup 12 Open 40

Shanghai Wok 18-22 Powered 150 Soup 12 Open 40

Chiu Chow Wok 18-22 Powered 150 Soup 12 Open 40

Chop Suey Wok 16-24 Open 80-130 or Jet

North American: East Coast Wok 16-24 Open 80-125 or Jet Soup 12

West Coast Wok 16-24 Ring, 50 -160 or Jet

6.6 CHINESE RANGE PERFORMANCE

6.6.1 Energy Efficiency The energy performance of Chinese ranges is not well docu• mented. No reported energy efficiencies were identified by this study, although unpublished energy consumption data were available for estimating energy consumption.

Technology Review of Commercial Foodservice Equipment Volume II, Page 6-5 Table 6.2 - Chinese Range Energy Efficiency3

Gas (%) Electric (%)

15-30 50-70 1 Best estimate based on authors' experience.

6.6.2 Energy Consumption An unpublished, proprietary end-use monitoring study showed that for all monitored equipment, woks consumed the largest measured daily energy consumption. Based on the median nominal chamber size of 500 mm (20 inches), a median energy input rate of 100 kBtu/h (an actual 500 mm diameter chamber is rated at 107 kBtu/h) and an estimated 10 hours of operation, an average energy consumption rate of 30 kBtu/h was calcu• lated for wok ranges. This corresponds to a duty cycle of 30%. The projected annual energy consumption was determined by assuming a 6-day, 52-week per year operation.

Table 6.3 - Projected Energy Consumption for Gas Wok Ranges

Nominal Rated Energy Duty Avg. Energy Typical Annual Energy Size Input Cycle Consumption Op. Hours Consumption

(wxd) (kBtu/h) (%) (kBtu/h) (h/d)a (kBtu)b

100-320

(Median) 2 Wok Range 200 30 60 10 187,000

'Operating hours or appliance "on time" is the total period of time that an appliance is operated from the time it is turned "on" to the time it is turned "off'. bThe annual energy consumption calculation is based on the average energy consumption rate x the typical operating hours x 6 days per week x 52 weeks per year.

6.6.3 Ventilation Requirements As for underfired broilers, the ventilation requirements for Chinese ranges are greater than for other categories of cooking equipment. Typical ventilation rates for a wall-mounted canopy hood range from 175-225 L/s (350 - 450 cfm) per linear foot, with 225 L/s (450 cfm) being recommended. The radiant heat gain from Chinese ranges contributes significantly to the heat gain of the kitchen. However, radiant factors are not published.

Technology Review of Commercial Foodservice Equipment Volume II, Page 6-6 6.7 RESEARCH NEEDS • End-use monitoring of Chinese ranges. • Development of a performance test method for woks and associated documentation of energy efficiency. • Characterization of energy balance of wok-cooking process. • Establishment of criteria for the development of a high ef• ficiency gas wok burner. • Development of an energy efficient Chinese range in part• nership with traditional Chinese range manufacturer.

6.8 REFERENCES 1. A Cahners Publication. 1992* Foodservice Equipment & Supplies Specialist. "Product Knowledge: Product Focus #109: Chinese Ranges", March, p.51. 2. Scriven, C. and Stevens, J., 1989. "Food Equipment Facts: A Handbook for the Foodservice Industry". Van Nostrand Reinhold (NY), Revised Edition, pp. 123 -124. 3. The Culinary Institute of America. 1991. "The New Profes• sional CheFM". Van Nostrand Reinhold (NY), Fifth Edition. pp. 393 - 394.

• 4. CP Publishing. Inc. 1995. Cooking for Profit. "Buyer's Guide", August 15, No. 531, p. 26.

l

Technology Review of Commercial Foodservice Equipment Volume H, Page 6-7 7. OVEN

7.1 INTRODUCTION An oven can be simply described as a fully enclosed, insulated chamber used to heat food. But, there are many variations of the basic concept in the commercial kitchen. This section describes the most common types: standard ovens (including range ovens and deck/pizza ovens), convection ovens (including cook & hold features) and combination oven/steamers (also known as combination ovens), conveyor ovens, and rotisserie oven/broilers. Ovens are moving from the back-of-the-house into the front-of- the-house in many restaurants. An increasing number of opera• tors are tooling up for the baking boom these days. They know that fresh-baked signature desserts, crusty breads, and familiar comfort foods such as muffins, cookies and bagels are irresisti• ble to their customers.'1' Another type of oven which has re• cently taken the market by storm is the barbecue/rotisserie oven. These ovens offer food service operators a unique opportunity to simultaneously cook and merchandise a variety of popular traditional foods: chicken, pork ribs, lamb, prime rib of beef. Pizza ovens too are making their debut in plain view of the customer in the more upscale operations. Conveyor ovens have enjoyed great success with pizza restaurants. Interestingly, a large seafood chain employs conveyor ovens for their complete menu production. Stimulated by the rapid growth of centralized food service cooking facilities, cook/chill systems and exhibi• FIGURE 7-1 Stacked, half-size convection tion baking and roasting operations, rack ovens are riding a [1] ovens. wave of popularity. Photo: The Blodgett Oven Company In addition to the traditional uses of ovens for roasting and baking, they may be used to cook a surprising range of foods usually associated with other appliances. For example, high- volume kitchens can use ovens to prepare large quantities of griddle standards such as bacon, eggs, sausages and French toast. "Oil-less frying" involves using a customized convection oven in place of a deep-fat fryer to cook French fries, onion rings, chicken nuggets, fish and other popular fried foods. Combination ovens are regularly used to proof dough, steam vegetables, cook and hold food, rethermalize pre-plated meals and broil steaks. Ovens represent the largest category in terms of types of units of any of the major cooking equipment categories.13' Their versa• tility makes them suited for virtually every type of food service

Technology Review of Commercial Foodservice Equipment Volume II, Page 7-1 operation. J A recent US study showed that 95% of commercial (non-institutional) operations reported having or using ovens; 98% of noncommercial (institutional) operations reported the same. The percentage of operations reporting using or having general bake ovens were 52% and 56%, respectively. Fifty per• cent of the operations in the commercial sector reported having and/or using convection ovens as compared to 83% of non• commercial operations. Pizza ovens accounted for 19% and 12%, respectively. Microwave ovens were popular in both sec• tors with 71% of the noncommercial foodservice sector and 70% of the commercial operations reporting having and/or us• ing them.m Commercial ovens are available in a multitude of sizes and cooking formats, using a variety of energy sources-electricity, natural gas, or liquid propane. Natural gas is the predominant fuel source for most commercial ovens. Ovens can be either free-standing or counter-top/stackable formats. Also, with com• petition heating up among manufacturers, more and more time- saving features via sophisticated control packages are being in• troduced. Pacific Gas and Electric Company has developed an ASTM standard test method for the performance of convection ovens which measures these parameters, and is in the process of com• pleting test methods for combination ovens and pizza (both deck and conveyor) ovens. These test methods are applicable to both full-size and half-size ovens and will allow manufacturers and end users to compare energy efficiencies, hence operating costs associated with different models, technologies and fuel sources.

7.2 COOKING PROCESSES Ovens cook food products by surrounding them with hot air. The defining process of each type of commercial oven is that it cooks by closely controlling the temperature and/or humidity of the oven cavity. The heat is transferred to the food using the three fundamental mechanisms for heat transfer either singly or in combination: convection, conduction, radiation, and in the case of combination ovens, steam. The processes are common to both gas and electric ovens.

Technology Review of Commercial Foodservice Equipment Volume II, Page 7-2 7.3 TYPES OF OVENS

7.3.1 Standard or Natural Convection Oven Standard or conventional ovens use natural convection and radi• ant heat to cook food products. In general, these ovens do not recirculate air. The burner or elements heat the air within the oven cavity causing currents of hot air which transfer heat to the surface of the food. The arrangement of pans in the oven and the texture of the food can affect the circulation of air, changing the cooking speed and uniformity. Two familiar types of standard ovens are the range oven and the deck/pizza oven. The range oven is the most familiar, since it is the kind most often found in residential applications. These ovens can be used for nearly all types of food preparation including breads, pies, meats, fish, poultry and baked potatoes. Because of a gentle environment as a result of not using blowers or fans to move air inside the oven cavity, standard ovens are ideal for precision baking. That is, baking sensitive pastry prod• ucts such as meringues, cream puffs, pastry shells and other products that require a dry atmosphere. Standard ovens are the least expensive to purchase, but they are not as fast-cooking or flexible as forced convection ovens. 7.3.1.1 Range Oven. The most common standard oven-the range oven, also known as the general purpose oven, is heated with atmospheric gas burners located directly below the oven cavity. Flue gases are routed around and/or through the cavity. In electric ovens the elements are placed in the top and bottom of the oven cavity, where they add both radiant and convective heat; they also may be placed underneath the bottom deck. Range, or under-range ovens, are part of a cooking unit or sys• tem. The range oven forms the housing or base for the range top (i.e., burners, griddle, etc.), addressed in Section 5. The range/ oven combination usually consists of the range system and only one oven cavity. Energy input ratings are typically given for the complete range system. Typically, the energy input rate of a range oven will be between 35 kBtu/h to 45 kBtu/h for gas and 7 kW to 9 kW for electric. Range ovens are normally specified for smaller operations. Their exterior dimensions are typically 900 mm (36") wide by 750 mm (30") deep by 750 mm (30") high. They typically come equipped with a pan support rack.

Technology Review of Commercial Foodservice Equipment Volume II. Page 7-3 7.3.1.2 Deck/Pizza Oven. Standard gas-fired deck ovens are much the same as a conventional roast or bake oven except the inside cavity has a low height, ranging from 150-250 mm (6"- 10"). It has a stationary, enclosed cavity and uses nonrecirc- ulated air. Heat may be transferred to the oven cavity from the combustion of gas either indirectly or directly. Indirect-fired ovens have the gas burners located below the bottom deck. The hot products of combustion heat the bottom, sides and top of the oven without entering the cooking cavity. Direct gas-fired ovens also have burners below the lower deck. However, the hot combustion products are directed through the cooking cavity rather than around the cavity as in indirect-fired units. Heat is transferred directly from the hot gases to the food. If an oven section has two compartments, they may or may not be independently heated and controlled. Usually the cavity walls are insulated with 50-100 mm (2"- 4") heat-stable fiber• glass, vitreous fiber or rock wool on the sides and top with 150 mm (2") in the swing-down door, Deck ovens, also called sectional ovens, are freestanding and stackable. one to three decks high. The differences between baking and pizza deck ovens are in size and energy input rates. Decks for baking ovens are commonly 840-1070 mm (33" to 42") wide and 915-1140 mm (36" to 45") deep. Pizza ovens range in width from 460-1990 mm (18" to 78%"), in depth from 560-1150 mm (22" to 45 V) and up to 1720 mm (673/4") in height. Baking Deck Oven. Baking deck ovens are often categorized as one-pan or two-pan ovens, depending on their ability to hold one or two standard baking sheets side by side. Each oven typi• cally has one or two oven cavities, or compartments. The com• partments are sized either for baking or roasting. Baking com• partments are about half the height of roasting compartments, generally 190 mm (7") vs. 380 mm (15"). The bottom of each compartment is called a deck; heat is usually supplied by burn• ers or elements under the deck. Some sectional ovens have op• tional steam injection to assist in finishing hard-crust breads. The ovens interiors are designed to absorb heat quickly and ra• diate the escaping heat back slowly and evenly. To accomplish this, the bottom of the interior, also known as the hearth, is of• ten made of ceramic material or steel, brick or composition material. Deck ovens with fire brick hearths are particularly good for bottom-crust baking and widely used for cooking bak• ery items and pizza. They also can be used to cook a wide vari-

Technotogy Review of Commercial Foodservice Equipment Volume II. Page 7-4 ety of foods fairly quickly: casseroles, breads, meats, fish. The limiting factor is the height or thickness of the food product. Pizza Deck Oven. The most common deck/pizza oven will hold six 300 mm (12-inch) diameter pizzas. Small countertop ovens will hold one to four pizzas. In most cases, the pizza pans are placed directly on the oven deck. Some manufacturers, recom• mend placing the pizza directly on the deck or hearth; others recommend using pizza screens or perforated pans for baking. In fact, they suggest reduced cook times plus improved product when using low, black aluminum, flat-bottomed pans rather than shiny or high-sided pans. ' Since the door is often opened to check doneness or break bubbles in the crust, at least one manufacturer offers an "air door" that retains oven heat with a vertical curtain of air inside the door opening. ] Good deck ovens designed with most of the attributes of good conventional ovens can be effective contributors to a food serv• ice establishment of average, moderate size. With deck/pizza ovens, a restaurant can not only satisfy its customer's appetite for pizza, but also do much of its oven cooking. Controls. Standard ovens usually have simple controls, limited to a thermostat and a selector that allows the oven to bake or broil. Sensors may be electronic, but are usually mechanical bulb type. Modulating thermostats, which adjust the burner in• crementally, are most common. Standard ovens have a tendency to be somewhat uneven in temperature distribution. On/off snap action thermostats which give better control are available but add to the initial cost. Gas deck/pizza ovens have shut-off and adjustment valves for the gas control and usually feature auto• matic safety pilots and ignition. Vents get rid of the generated steam and provide crisp crusts on the pizzas.

7.3.2 Convection Oven Reflecting years of technological refinements, today's convec• tion oven is one of the most significant developments in the food service industry. It originated as a modified conventional or standard oven developed to overcome the problem of uneven temperature distribution in the cooking cavity and to provide more oven capacity for a given size. Given these characteristics, the convection oven has naturally spawned a vast number of variations in terms of size, technology, capacity, and type. They are available in gas and electric. Hot air is forced through fans to circulate around the food, cooking it evenly and quickly. The concept behind the forced- air convection oven is a simple one. When food is placed inside

Technolog> Review of Commercial Foodservice Equipment Volume II. Page 7-5 the oven, it is surrounded by an insulating layer of cold air. A motorized fan (or blower) blows heated air throughout the oven's cavity, striping away the layer of cold air next to the food. The result is a faster, more even cooking process than that provided by standard, radiant-heat ovens. Forced convection reduces the cook time significantly and allows more food to be cooked in each load. Most gas convection ovens use atmospheric rather than infrared burners although, recently manufacturers have introduced sev• eral convection oven models featuring IR burners. Gas convec• tion ovens are available with single or multiple burners. Histori• cally, most gas convection ovens are indirectly fired. Burners are usually located at the bottom of the oven cavity, or between the cavity and the insulated oven wall. Just recently, the Blodgett Oven Company introduced a new direct gas-fired heating system that places the burner in the oven cavity. This 38 kBtu/h burner has an electronic hot surface ignition system. Manufacturers differ in how they route the flue gases and how they mix them with cavity air. Gas burners may be protected from air currents by an arrangement of baffles, and the flue gases directed around or through the cavity. Alternatively, the flames and flue gases may be directed into tubes that act as heat exchangers and vent into the flue. The oven cabinets are well- insulated. The oven walls are usually insulated by at least 4" of rock or mineral wool, marinite or pressed vitreous fiber to retain heat within the cooking cavity. Forced convection ovens may come in "full-size" or "half-size" capacities, depending on whether they are dimensioned to ac• cept standard full-size (460 x 660 x 25 mm (18" x 26" x 1")) or half-size (460 x 330 x 25 mm (18" x 13" x 1")) sheet pans. Full- size ovens have large interior cavities capable of handling up to six full-size pans. Ovens which offer extra depth cavities offer a choice of pan direction placement to enhance heat circulation. Half-size models accommodate up to five half-size pans. Countertop models and range ovens are also available, as are high-capacity roll-in or rack ovens. The convection principle has also been applied to conveyor and rotisserie ovens. 7.3.2.1 Rack Oven. Rack ovens are basically tall stainless steel boxes capable of high production in a relatively compact space. These large capacity roll-in rack models fill the require• ments of high volume institutional operations. They are ideal for rethermalizing many products prepared in cook/chill sys• tems as well as baking and roasting. The rack oven is capable of

Technology Review of Commercial Foodservice Equipment Volume II. Page 7-6 producing thousands of identical products or many diverse menu items quickly within the same cooking cavity. The product is placed in pans that are loaded on mobile, stain• less steel or aluminum racks. The loaded racks are rolled into the oven through a large vertical entrance door. The rack is con• nected to a turning device that starts smoothly and rotates slowly in a carousel motion. This method of cooking contrib• utes to the cooking speed and product consistency. Rack ovens can handle single or double rack loads. They typi• cally have a capacity of 20 to 40 standard sheet pans. They are available in models requiring 1.5 -1.9 square meters (16 to 20 square feet) of floor space and have rated inputs ranging from 125 kBtu/h to 375 kBtu/h. Rack ovens have heat exchangers of various designs that function with a power blower to circulate heat evenly throughout the cavity. Self-contained steam systems are available for injecting steam into the oven cavity at the right moment. ' 7.3.2.2. Combination Oven/Steamer. Combination oven/ steamers, or combination ovens, are convection ovens with the added capability to inject steam into the oven cavity. It offers three distinct cooking modes. In the combination mode it pro• vides a way to roast or bake with moist heat (hot air and steam); in the convection mode it allows for roasting or baking the stan• dard convection way (dry, hot air); or it can serve as a straight pressureless steamer, discussed in Section 8. In addition, some manufacturers provide holding and proofing temperature set• tings. Others offer high-end temperatures exceeding 290°C (5SOT) to enable using the oven as a broiler. A study171 at PG&E's Food Service Technology Center showed that the combination ovens cost 30% more per load when cooking a fully loaded oven of chickens in the combination mode than in the convection mode. The cook time in each combination oven tested was reduced by cooking in the combi• nation mode, although the time difference varied from oven to oven. Also, the cost to preheat an oven in the combination mode was about double that of the convection mode's cost because the boiler must be preheated in the combination mode. Until quite recently, electric combination ovens dominated the market place. But now, a growing number of manufacturers of• fer gas combination ovens as well. Many models are available. They start with smaller countertop sizes, which handle half-size 3/fr 3 M (264 x 324 x 65 mm (10 x 12 /4 x 2'/2")) steam table pans. Full-size combination ovens are capable of handling loads of up l to 12 full-size (300 x 510 x 65 mm (12 x 20 x 2 /2")) steam table

Technolog) Review of Commercial Foodservice Equipment Volume II, Page 7-7 pans. They extend to large, floor-mounted, full-sized units that accept up to 20 standard 460 x 660 mm (18 x 26") sheet pans. Large capacity roll-in rack models are also available. Cook-and-Hold Feature. Some ovens are designed specifically for cooking and holding product. Others are normal temperature standard or convection ovens (including combination and rotis- serie ovens) which offer low-temperature cooking options, or cook-and-hold modes. This feature is primarily used to roast and hold meats. Unlike conventional ovens that blast direct dry heat, the cook- and-hold oven uses constant, uniform, moist heat which results in less shrinkage. Also, longer cooking periods at reduced tem• peratures, between 80°C and 120°C C (175°F and 250°F) vs. 135°C to 200°C (275°F to 400°F) for conventional cooking methods help to retain juiciness as well as tenderness. Two types of cook-and-hold ovens exist. One uses natural con• vection with high humidity (90 - 95% humidity with minimal air movement) and slightly higher temperatures; the other uses forced convection with lower temperatures and lower humidity levels (between 30 - 60% humidity). ' The basic frame, housing and interior components are the same as those in a forced convection oven. The main difference is that the cook-and-hold oven is able to produce relatively high hu• midity during the cooking process, This is usually accomplished through the use of a water reservoir within the oven cavity. The forced convection cook-and-hold ovens use a blower to evenly distribute the moist heat throughout the oven cavity. Cook-and-hold ovens are available in both gas and electric models. They are available in the same general sizes and the same rated energy inputs as basic convection ovens.

7.3.3 Conveyor Oven Conveyor ovens are available using five different heating proc• esses: infrared; natural convection with a ceramic baking hearth; forced convection; air impingement; or a combination of infra• red and forced convection. The forced convection and air im- pinger ovens use a blower to move the air within the oven cav• ity. In general most forced convection conveyor ovens may be classified as air impingers. The "fingers" of air blow away the layer of air and moisture that insulates the food, thus increasing the speed of the cooking process. Conveyor ovens are generally used for producing a limited number of products with similar cooking requirements at high

Technolog> Review of Commercial Foodservice Equipment Volume 11. Page 7-8 production rates. They are highly flexible and can be used to bake or roast a wide variety of products including pizza, casse• roles, meats, breads, and pastries. The ovens are available in many different sizes and configura• tions. They are available in sizes small enough to appeal to low- volume operations that do not specialize in pizza, and short cook times make them an appealing choice for high volume op• erations as well. Most ovens can be stacked up to three units high, significantly increasing production capacity without re• quiring increased floor space or be placed end-to-end to effec• tively double the cooking capacity. Essentially, conveyor ovens are a rectangular housing contain• ing a baking cavity or chamber which is open on two opposing sides. A conveyor system carries the food product through the baking chamber or tunnel on a wire rack. Most ovens can be outfitted with multiple conveyor belts, each of which may have a different operating speed. The typical counter-top unit has a conveyor width as small as 250 mm (10") and a tunnel length of 350 mm (14"). Freestanding units may have conveyor widths which range from 350 mm-950 mm (14M—37") and tunnel lengths range from 500-1900 mm(20"- 75"). Oven controls ad• just both the heat input and speed of the conveyor. Top and bottom heat are independently adjustable. Some conveyor ovens have a hinged glass door along side of the tunnel to allow load• ing and unloading of food that requires a shorter cook time. Newer conveyor oven designs may incorporate multiple cook• ing zones within the cooking chamber, with three cooking zones being typical. The temperature within each zone may be inde• pendently adjusted. The first zone is very hot, and as the prod• uct passes through it, it is quickly heated up to cooking tempera• ture. Before it starts to burn, the product is moved into the sec• ond zone, which is maintained at a considerably lower tempera• ture. In this zone the product cooks at an even rate until it reaches the third zone, generally referred to as "the finishing" zone. Here the temperature is even lower, cooking the product to the desired degree of "doneness". One manufacturer has expanded upon the multiple zone concept by allowing each eight-inch length of tunnel to have a different operating temperature. Another manufacturer has developed a special "aerodynamic air flow" system to reduce the cook time even more.[ ! A few manufacturers offer a feature often referred to as an air curtain, which helps to keep the heated air inside the conveyor oven. Thus, less energy is required to keep the oven at operating

Technolog} Rev iew of Commercial Foodservice Equipment Volume II, Page 7-9 temperature, which in turn reduces the thermal load on the kitchen's HVAC system.'41 Controls. In general, convection ovens, including conveyor ovens as well as rotisseries, offer more control over cooking than standard ovens. Convection ovens generally use accurate electronic sensors and thermostats. Many gas models feature electronic ignition and controls. Also, most of the newer gas and electric models have programmable cooking computers which recall several cooking sequences by the simple press of a but• ton. Some ovens are programmable to first cook and then hold food products. That is, food may be cooked at a high tempera• ture with high convection and then held for an extended period at a lower temperature with the fan off. Some ovens allow the user to control cooking by regulating fan speed as well as temperature, humidity and the cooking time. (The speed of the fan affects cook time and uniformity, as does the pattern of airflow through the interior.) In combination ov• ens, for example, a cook cycle may be programmed to begin with high steam and convection, continue cooking with convec• tion only, and hold the finished product at low temperature and humidity. Other options included in many of the combination ovens are a low-speed fan setting to permit cooking of delicate items and a rapid cool down mode to facilitate going from oven to steaming quickly.

7.3.4 Rotisserie A rotisserie is fitted with one or more mechanically rotated spits that hold meat or poultry in position near a fixed heat source while the food is slowly being cooked on all sides. The heat source may be gas or electricity. Several models also offer wood-fired enhancement systems. Rotisseries can be separated into two main categories: rotisserie ovens and rotisserie broilers. Within these, many models are available. 7.3.4.1 Rotisserie Oven. Rotisserie ovens are designed for batch cooking, with individual spits arranged on a rotating wheel or drum within an enclosed cooking cavity. The ovens can be equipped with either single action rotation cooking or a dual rotating action, planetary cooking system that incorporates convection, radiant, and air impingement cooking. Motors pro• vide the labour saving power to rotate both types of cooking systems. For gas rotisserie ovens a number of gas-fired burner systems are available. Single heat-source systems include atmospheric flame type, radiant and infrared. There also are dual burner

Technolog\ Review of Commercial Foodservice Equipment Volume II, Page 7-10 systems that combine infrared with an open flame and radiant heat. Most gas models feature electronic ignition systems. Rotisserie ovens range in size from high-volume floor models to space-saving countertop models. Most models are equipped with basic time and temperature controls, optional cook-and- hold controls, or more sophisticated control packages with pro• grammable channels. Electric models may feature interior halo• gen merchandising lights. 7.3.4.2 Rotisserie Broiler. The rotisserie broiler is designed for continuous loading and cooking, with vertically stacked spits. Some models feature individual drive systems which utilizes a chain link from gear to gear to maintain the tension to allow op• eration of one or more spits at any time. The rotisserie broiler employs super heated fire bricks strategically located over pow• erful pipe burners (e.g., 40 kBtu/h each with a total input rate between 105 kBtu/h to 120 kBtu/h for a median of 112 kBtu/h, or roughly twice that of the rotisserie oven at 50 kBtu/h), which in turn, emanate radiant heat. Unlike rotisserie ovens, rotisserie broilers have very rudimentary controls.

7.3.5 Advanced Oven Technologies Over time, manufacturers have metamorphosed the standard or natural convection oven into the modern-day forced convection oven simply by adding a fan. More efficient infrared burners are replacing the traditional atmospheric burners in gas ovens; quartz halogen lamps which cook food using a combination of infrared energy and visible light, circulating thermal fluids, and a combination of microwave and convection are playing a part in electric oven designs. Combining technologies such as infra• red with forced convection or convection with steam injection, recirculating combustion gases via specially designed fans or recycling tubes all add up to improved oven performance. Ad• ditionally, oven manufacturers are coupling ventilation hoods with their oven designs. 7.3.5.1 Infrared Burners. An infrared/forced convection oven combines the penetrating heat of infrared radiation with the convective effect to sharply reduce baking time compared to natural convection ovens. 7.3.5.2 Air Impingement. Air impingement is a relatively new technology applied to conveyor and some rotisserie ovens. Air impingement typically uses a ported manifold to direct jets of air, or "fingers," onto the product's surfaces.

Technology Review of Commercial Foodservice Equipment Volume 11. Page 7-11 7.3.5.3 Quartz Halogen Lamps. Quadlux, Inc., the Northern California manufacturer of the Flashbake® pizz^ake oven uses quartz lamps to cook food using a combination of infrared energy and visible light. The infrared energy cooks from the outside in, browning and crisping the exterior as would a con• ventional oven. The visible light penetrates into the food a short distance, with the depth varying depending on the colour and composition of the food. The quartz lamps used in the oven de• sign were first used to cure silicon chips for the microprocessor industry. The lamps start up instantly, thus have no preheat time, and remain off when idle. This oven however, typically uses as much or more energy than conventional ovens when cooking.' ] 7.3.5.4 Conduction. Heat is transferred to the foods via direct contact with a heated medium. For example, many pizza ovens incorporate a firebrick or composite hearth with burners or ele• ments underneath them. The bottom of the pizza is cooked by direct contact with the hot hearthstone. This process of conduc• tion, combined with the circulation of hot air above the pizza, allows good control of the cooking speed and texture of both the crust and toppings. Another recent entry into the market place is an electric cook-and-hold conduction oven which circulates heat transfer fluids through the oven's heat transfer plates. The heat is conducted directly through the pans to the food. This method of heat transfer, according to the manufacturer, allows food to be brought evenly to a cooked state without burning or drying. 7.3.5.5 Combination Convection Microwave. Three fairly new technology ovens on the market"0] combine convection with microwave for high-speed cooking. The TurboChef® uses a modified impingement system that propels hot air directly down onto the food, then pulls it around and underneath the product. This oven is frequently supplied with a built-in micro• wave to further speed the cooking process. Lincoln Foodservice, has spent nearly three years developing its own new technology oven that uses both their air impingement and microwave cooking technologies with similar results. Among the innovations that the AIM™ promises are computer- controlled focusing of the hot-air impingement above and be• low; a nonrotating cooking service, which means that the whole oven can be used to prepare food; and an innovative microwave technology which will permit the use of metal trays and pans. Amana's new Convection Express is being touted as the first commercially approved compact oven for foodservice use. It packs a "double whammy", offering 1000 watts of microwave

Technology Review of Commercial Foodservice Equipment Volume II. Page 7-12 energy and 2,200 watts of convected air. With the cooking combination comes a host of usage options: browning, baking, steaming, sauteing, cooking and roasting. Also, users can pro• gram items through up to four different cooking stages. A fro• o zen dish can, for example, first be defrosted through the micro• wave-only function, then put through a fast-heating stage on a convection cycle, then baked by both microwave and convec• tion heat and, finally, browned with a dose of convection-only heat.

7.4 OVEN PERFORMANCE The ASTM Standard Test Method for Convection Ovens11 u2] developed at PG&E quantifies thermostat accuracy, energy in• put rate, preheat energy and time, idle energy rate, cooking en• ergy efficiency, production capacity and cooking uniformity. These criteria also can be applied to the other types of ovens described in this Section. PG&E is in the process of developing similar methods of test for combination ovens, deck and con• veyor pizza ovens and rotisserie ovens.

7.4.1 Thermostat Accuracy The ASTM method reports how close the actual oven tempera• ture is to the temperature selected at the controls.

7.4.2 Energy Input Rate Energy input rate is one of the basic criteria for oven selection. It is the maximum rate at which an appliance draws energy, ex• pressed in kBtu/h or kW. The more power an oven has, the faster it can preheat and recover to cooking temperature. This is important for achieving high production rates. Energy efficiency is also a factor. An inefficient oven may have a higher input rating and still not perform as well as a more efficient oven.

7.4.3 Preheat Energy and Time These two criteria measure the time and energy it takes to raise the temperature of the oven to cooking temperature. Some ov• ens may be left on all day if they are slow to preheat or their usage cannot be scheduled, as is the case with pizza ovens. Pre• heat time also gives an indication of how fast the oven recovers when the oven door is opened and closed; this is important to maintaining a steady cooking temperature.

Technology Review of Commercial Foodservice Equipment Volume II. Page 7-13 7.4.4 Idle Energy Rate The idle energy rate is the amount of energy consumed per hour when the oven is holding temperature without a load. Some ov• ens, especially pizza ovens, spend much of their time "idling". Depending on the oven, this can incur a significant annual cost.

7.4.5 Production Capacity Production capacity is the amount of food that can be prepared in an oven in a given time period. It is one of the most important factors in selecting the right oven for a kitchen. For convection ovens, the ASTM method determines this number by cooking loads of potatoes; the result is reported in pounds of potatoes per hour. PG&E testing showed production rates of approxi• mately 32 Kg (70 lb) per hour for both the gas and electric full- size convection ovens and around 18 Kg (40 lb) per hour for the half-size ovens tested.1 ' For the other three types of ovens, in• put energy rating and oven cavity size are usually taken as indi• cators of production capacity. Manufacturer's product literature provides a variety of benchmarks in terms of cook times and load sizes for products such as pizzas, chickens and loaves of bread.

7.4.6 Cooking Uniformity Cooking uniformity is the ability of an oven to cook food evenly no matter where it is placed in the oven or how the oven is loaded. The ASTM method of test for convection ovens checks uniformity by baking a fully loaded oven of white sheet cakes and comparing the browning patterns. Cake-browning tests at PG&E showed uneven cooking patterns from front-to- back and from rack-to-rack for all ovens tested.'121 A poorly de• signed oven may burn food on the top rack before it finishes cooking the food on the center rack. Convection ovens with un• even air flow may burn the side of the food closest to the fan while the other side is barely browned. A variety of advanced burners is being developed by the gas industry which will improve the heating uniformity in the burner section through the use of ported infrared burners and inconel wire mesh burners. These developments should improve baking performance.

7.5 BENCHMARK ENERGY EFFICIENCY The ASTM Standard Test Method for Convection Ovens'1 de• veloped at PG&E allows manufacturers and users to compare

Technologj Re\ie\\ of Commercial Foodservice Equipment Volume 11. Page 7-14 the cooking energy efficiency of different ovens. This method applies to general purpose, full-size and half-size convection ovens which are used primarily for baking. It is not applicable to ovens used for slow cooking and holding, deck ovens or large o roll-in rack type ovens. Cooking efficiency as defined by the ASTM Standard is the ra• tio of energy added to the food and total energy supplied to the appliance during cooking: p CookingEfficiency = — x 100% £. Appliance Energy efficiency is determined by baking a fully loaded oven with potatoes (i.e., 30 potatoes per sheet pan per rack x 5 racks for full-sized ovens; 15 potatoes per half-sheet pan per rack x 5 racks for half-sized ovens). Each load of potatoes is cooked until the bulk temperature of the total load reaches 98.9°C (210°F). Typical energy efficiencies for convection ovens under these cooking scenarios, along with the other oven types are summarized in Table 7-1. Gas ovens, by the very nature of their heat transfer from the combustion of gas are less efficient than their electric counter• part. In standard gas ovens the combustion chamber and flue passages are located between the oven cavity and the exterior cabinet. The hot products of combustion indirectly heat the oven cavity by conduction through its walls. The hot flue passages also may be close to the exterior, causing heat losses to the en• vironment. Modern convection ovens circulate flue gases through passages built into the oven cavity walls resulting in

TABLE 7-1 Oven Energy Efficiency8

High Eff. Gas <%) Std. Gas <%) Elec. (%)

Std/Conv/Comb 40-50 30-40 50-80 Deck 20 - 30 40 - 60 Conveyor 10-20 20-40 Rotisserie 20 - 30 50 - 60

* Energy efficiency numbers are based on PG&E test data from applying the ASTM Standard Test Methods to convection ovens, and on preliminary estimates for com• bination ovens, deck and convevor pizza o\ ens. and rotisseries.

Technology Review of Commercial Foodservice Equipment Volume II. Page 7-15 better thermal coupling and significantly improved efficiency. Two types of recirculation systems are currently available: one uses a specially designed fan, the other uses a recycling or 'snorkel' tube. Both systems reuse the air which would nor• mally be vented. Also, differences in the combustion system account for variance in energy efficiencies. Low combustion efficiency in a gas oven can be caused by excess air and poor heat transfer to the oven cavity. The most efficient ovens will use the minimum quanti• ties of excess air and keep the exiting flue temperature as close as possible to the cavity temperature. As pointed out by A.D. Little in their characterization of com• mercial ovens, efficiency improvements of gas-fired ovens has consisted mainly of controlling burner excess air through the use of power burners.ll3) Convection oven technology can also be viewed as an energy conserving measure since the cooking time associated with convection cooking is shorter, thus reduc• ing the overall energy consumption required during the cooking event. Direct-fired ovens, consequent to the gas flame being in direct contact with the oven cavity and food products being cooked, require less energy to do the same amount of work as indirect-fired ovens. A.D. Little projects energy efficiencies as• sociated with these ovens to be in the 45% range. They also speculate that the successful application of air impingement to conveyor ovens will drive the efficiency of these gas models into the 40% range versus the current 10% - 20% limits.

7.6 OVEN ENERGY CONSUMPTION Projected energy consumption for gas and electric ovens are presented in Table 7-2 and 7-3. Based on PG&E's in-kitchen monitoring at its production-test kitchen, average energy con• sumption rates for convection ovens reflect duty cycles of 35% for a full-size gas convection oven, 40% for a half-size gas oven and 25% for both electric full-size and half-size ovens1' '. It was assumed that the usage patterns for countertop models would be similar to half-size convection ovens. Duty cycles for deck ovens were assumed at 30% for gas ovens and 20% for electric ovens based on data from a proprietary un• published end-use study. Similarly, a duty cycle of 50% was assumed for both gas and electric conveyor ovens. Rotisserie duty cycles were based on data generated by PG&E's Food Service Technology Center. The duty cycle of an appliance is defined as the average rate of energy consumption expressed as

Technologv Review of Commercial Foodservice Equipment Volume II. Page 7-16 a percentage of the rated energy input or the peak rate at which an appliance can use energy. Daily energy consumption for ovens were calculated by multi• plying the median rated energy input for each oven category by the respective duty cycle and the hours of operation. Typical operating hours were gleaned from in-kitchen energy-use monitoring experiences and observations as well as on the PREP study' ' and proprietary end-use monitoring reports. Projected annual energy consumption was determined by as• suming a 6-day per week, 52-week per year operation.

7.7 VENTILATION REQUIREMENTS Some recent building codes and guidelines reflect the differ• ences between gas and electric oven characteristics, while others do not. The 1995 ASHRAE Applications Handbook classifies both gas and electric ovens as light duty with respect to ventila• tion requirements. Typical ventilation rates for a listed (e.g., ULC), wall-mounted, canopy hood range from 75-100 L/s (150 - 200 cfm) per linear foot.|io] Ovens may be equipped with a standard draft hood which may be directly vented to a flue or chimney. This may eliminate the need for an exhaust hood for these ovens when used to prepare food product that does not produce grease. 7.7.1 Integrated Ventilation Systems. Several oven manufac• turers have integrated appliance-specific ventilation hoods in their oven designs. Designing hoods for a given model, elimi• nates the risk of mismatched or incompatible equipment. The In-Vent™ integrated ventilation hood for Blodgett's Master- Therm conveyor oven is a revolutionary new vent system de• signed to minimize heat gain—both radiant and convective as well as the net exhaust requirement. Its unique configuration surrounds the majority of the oven's exterior and makes opti• mum use of untempered make-up air. This, in turn, reduces the load on the restaurant's HVAC system while providing in• creased operator comfort. Also, because of its enclosed nature, this system is quieter than canopy hood ventilation systems. Another company-Franklin/Southern Pride-has integrated a hood with their rotisserie system. Although the system is cur• rently restricted to the rotisserie oven, Franklin plans to accom• modate their other ovens in the near future.

Technology Review of Commercial Foodservice Equipment Volume II. Page 7-17 TABLE 7-2 Projected Energy Consumption for Gas Oven

Nominal Rated Energy Duty Avg. Energy Typical Annual Energy O Size Input Cycle Consumption Op. Hours Consumption a (wxd) (kBtu/h) (%) (kBtu/h) (h/d) (kBtu)b STANDARD/CONVECTION/COMBINATION Full Size 38"x38" 40-100 (Median) 70 35° 25 62,400

Half Size 30" x26" 20-40 (Median) 30 40e 12 22,500

Countertop 20" x22" 15-20 (Median) 18 40* 8,740

DECK9 20-120 (Median) 70 30" 21 10 65,500

CONVEYOR 120-150 (Median) 135 50' 68 10 212,000 ! )

ROTISSERIE 40-60 (Median) 50 60J 30 74,900

Operating hours or appliance "on time" is the total period of time that an appliance is operated from the lime it is turned "on" to the time it is turned "off. 'The annual energv consumption calculation is based on the a\erage energv consumption rate x the typical operating hours x 6 da> s per week x 52 weeks per year. "Includes cook & hold ovens, dThe duty cycle is based on monitoring a full-size gas convection oven with an input rate of 72 kBtu/h in a real-world pro• duction kitchen.,,J1An associated average energy consumption rate of 25 kBtu/h was calculated. eThe duty cycle is based on monitoring a half-size gas convection oven with a rated input of 35 kBtu/h in a real-world pro• duction kitchen. "^ An associated a\erage energy consumption rate of 12 kBtu/h was calculated. 'A 40% dut\ cycle has been assumed for countertop ovens based on the assumption that the usage pattern is similar to half- size oven operations. includes bake, roast, combination and pizza ovens. ''A 30% dut\ cycle has been assumed for deck ovens based on data from an unpublished proprietary end-use monitoring study. 'A 50% dul\ c> cle has been assumed for conveyor ovens based on data from an unpublished proprietary end-use monitoring stud\. 'A 60% dut> c\cle has been assumed based on PG&E laboratory rotisserie testing.'7'

Technology Review of Commercial Foodservice Equipment Volume II, Page 7-18 TABLE 7-3 Projected Energy Consumption for Electric Oven

Nominal Rated Duty Avg. En. Typical Annual Energy Size En. Input Cycle Consum. Op. Hrs. Consumption

a c (wxd) (kW) (%) (kW) (h/d) (kWhf (kBtu)

STANDARD/CONVECTION/COMBINATIONd Full Size 38"x38n 10-40

(Median) 25 253 12,500 42,600

Half Size 30"x26" 6-10 (Median) 8 25* 3,740 12,800

Countertop 20" x 22" 2-6 (Median) 4 259 1,250 4,260

DECK" 6-12 (Median) 9 20 10 6,240 21,300

CONVEYOR 35-45 (Median) 40 50* 20 10 62,400 213,000

ROTISSERIE 4-12

(Median) 8 65" 8 12,500 42,600

"Operating hours or appliance "on lime" is the total period of time that an appliance is operated from the time it is turned "on" to the time it is turned "off'. ''The annual energv consumption calculation is based on the average energy consumption rate x the typical operating hours x 6 da\ s per week x 52 weeks per year. "Conversion Factor: I kW = 3.413 kBtu/h. dlncludes cook & hold ovens. =The duty cycle is based on monitoring a full-size electric convection oven with an input rate of 16 kW in a real-world pro• duction kitchen.1'6'An associated average energy consumption rate of 5 kW was calculated. fThe duty c\ cle is based on monitoring two half-size electric convection ovens with a rated inputs of 5 kW each in a real- world production kitchen.'' "' ' An associated average energy consumption rate of 2 kW was calculated. SA 25% duty cycle has been assumed for countertop ovens based on the assumption that the usage pattern is similar to half- size oven operations. h!ncludes bake, roast, combination and pizza ovens. 'A 20% dut\ cvcle has been assumed for deck ovens based on data from an unpublished proprietary end-use monitoring stud\. JA 50% duty cvcle has been assumed for conveyor ovens based on data from an unpublished proprietary end-use monitoring stud\ A 60% dut\ cvcle has been assumed based on PG&E laboratory rotisserie testing. m

Technology Review of Commercial Foodservice Equipment Volume II. Page 7-19 7.8 RESEARCH NEEDS Potential research areas include: • Insulation: Good insulation is a fundamental energy saving o feature that applies to all types of ovens. So, comparing the thickness of insulation in different ovens within the same category would quantify its affect on energy use, hence en• ergy efficiency. For example, increased insulation around the oven cavity will influence the idle energy consumption rate as well as the recovery time. • Enhanced temperature control: Slow recovery (i.e., the time it takes the oven to reach the temperature set point from unloading to reloading the oven) and poor temperature controls (i.e., thermostat accuracy) may result in the opera• tor setting higher than necessary cooking temperatures, thereby increasing heat losses to the kitchen. • Performance benchmarking: Apply ASTM test methods to direct-fired ovens to determine the energy efficiency as• sociated with this design versus that of the more common indirect-burner design used in the majority of ovens on the market. • Combined technologies: Identify and investigate combined technologies for gas ovens visa-vie microwave/convection technology used in electric ovens.

7.9 GAS INDUSTRY MARKET FOCUS As with other classes of cooking equipment, the primary factor determining the future average efficiency of ovens will be the factors that lead end users to purchase more efficient commer• cially available equipment and to a lesser extent on any future technology developments. There is a need for the gas indus• try to better benchmark oven energy performance for all types of ovens. Further more, an opportunity exists for the gas utilities to promote higher efficient, direct-fired ovens over the more common underfired models.

7.10 REFERENCES 1. A supplement to Restaurant Business Inc., 1995. Foodserv• ice Equipment 1000 for NAFEM. "The Baking Boom", p.53-54. 2. CP Publishing. Inc. 1994. Cooking for Profit. "Rack/Tray Ovens", September 15, No. 520, p. 14 -15.

Technology Review of Commercial Foodservice Equipment Volume II. Page 7-20 3. "Opportunities and Competition in the Food Service Equipment Industry'*: A presentation by R. Simek. Senior Consultant, Arthur D. Little to The New England Gas As• sociation, 1995, February 10. 4. Architectural Energy Corporation, 1991. Foodservice Equipment Volume 2: Ovens, Prepared for Southern Cali• fornia Edison Technology Assessment, Volume 2, Decem• ber. 5. CP Publishing. Inc. 1993. Cooking for Profit "Gas Deck/Pizza Ovens", July 15 - August 14, No. 506, p. 16 - 17. 6. CP Publishing, Inc., 1990. Cooking for Profit. "Gas Con• vection Ovens", May 15, No. 468, p. 4-5. 7. PG&E, 1995. "Appliance Testing for a Deli Operation." PG&E Products and Services Report No. 5016.95.23, April. 8. Unpublished. Increasing Profits by Using Energy Efficient Food Preparation Equipment, Processes and Procedures: a Cooking Equipment Module prepared by Fisher, D.R., The University of Manitoba for Energy. Mines & Resources Canada, March. 9. Esource Inc., 1995. "Exclusive Reports on Energy End-Use Efficiency Product Profile: The FlashBake Oven." PP-95-1, February. 10. Binder, M. in Pizza Today., published monthly by ProTech Publishing and Communications (New Albany, IN), 1995. August, Volume 13, Number 8, pp. 44 - 48. 11. ASTM Standard Test Method for Performance of Convec• tion Ovens: Designation F1496-93, 1994. In Annual Book of ASTM Standards, Philadelphia. 12. PG&E. 1994. "Development and Application of a Uniform Testing Procedure for Convection Ovens" prepared for the Research and Development Department, October. 13. Little, Arthur D. Inc., 1993. "Characterization of Commer• cial Building Appliances": Final Report for Building Equipment Division Office of Building Technologies U.S. Department of Energy, August, pp. 5-38. 14. PG&E, 1995. "Montague Model SE70AH Gas Full-Size Convection Oven: Appliance Performance in Production." PG&E Products and Services Report No.5011.95.21, Publi• cation pending.

Technologv Review of Commercial Foodservice Equipment Volume II. Page 7-21 15. PG&E, 1992. "Appliance Performance in Production Blodgett Model DFG-60 Gas Half-Size Convection Oven." PG&E Research and Development Report No.008.1 -9.11, December. 16. PG&E, 1995. "Montague Model SEK15AH Electric Full- Size Convection Oven: Appliance Performance in Produc• tion." PG&E Products and Services Report No.5011.95.22, Publication pending. 17. PG&E, 1995. "Blodgett Model CTB-1 Electric Half-Size Convection Oven: Appliance Performance in Production." PG&E Products and Services Report No.5011.95.17, Publi• cation pending. 18. PG&E, 1990. "Cooking Appliance Performance Report: PG&E Production-Test Kitchen." PG&E Research and De• velopment Report No. 008.1-90.8, May. 19. Claar, C.N., Mazzucchi, R.P., Heidell, J.A., 1985. "The Project on Restaurant Energy Performance (PREP) -End- Use Monitoring and Analysis." Prepared for the Office of Building Energy Research and Development, DOE, May. 20. ASHRAE. 1995. Applications Handbook. "Kitchen Venti• lation", Chapter 28, pp. 28.1-28.20.

Information in this module also references Manufacturers Prod• uct Literature, catalogues, and appliance specification sheets.

Technology Review of Commercial Foodservice Equipment Volume 11. Page 7-22 8. COMPARTMENT STEAMERS

8.1 INTRODUCTION Commercial compartment steamers provide an easy, fast way to prepare large quantities of food. Steaming offers good nutrient retention, short cook times, and ease of preparation: little atten• tion is needed from the chef, food can be cooked and served in the same pan and cleanup is simple. Steamers are versatile ap• pliances that can be used to prepare almost any food that does not require a crust. Delicate vegetables such as asparagus and broccoli are cooked without damage, frozen foods are defrosted and cooked in one step and meat can be wet-roasted with less weight loss than oven roasting. In appearance the steamer resembles an oven. The cavity is rectangular on atmospheric steamers, and may be oval or round on pressure steamers (atmospheric and pressure steamers are described in detail in section 8.3). The door is gasketed and windowless. Controls are front mounted. Steamers come in a variety of configurations, including counter- top models, wall mounted models and floor models mounted on a stand, pedestal or cabinet-style base. A steamer may consist of FIGURE 8-1 one to four stacked cavities or "decks". The cavity is usually Two-compartment convection steamer on self-contained base. designed to accommodate a standard 300 mm x 500 mm (12" x Photo: Market Forge Company® 20") hotel pan. Smaller steamers may be designed for use with one-third size pans, and some large steamers can hold several 460 mm x 660 mm (18" x 26") baking trays. The steam itself can be produced in several ways. Many steam• ers have an internal steam generator, generally a gas or electric boiler. In this case, there may be an additional steam takeoff to power other appliances such as a small steam jacketed kettle mounted on the steamer's cabinet base. The internal steam gen• erator may also be a well in the oven cavity heated by immersed electric elements, or water sprayed on the heated floor of the cavity. The steam may also come from an external source. If this steam is clean, it can be routed directly to the steamer compartments. Otherwise, it can be run through a heat exchanger and used to generate potable steam from clean water. Steamers generally require a drain line and a water line as well as gas, electric or direct steam connections. Self contained units typically have boilers that fill automatically. Condensate from the cavity is directed to a drain tube, where it is cooled by a

Technology Review of Commercial Foodservice Equipment Volume II, Page 8-1 stream of water before flowing into the sewer. (In many areas it is against code to drain water above a certain temperature.)

8.2 COOKING PROCESS Steam cooking exploits the fact that steam at (100°C) 212°F carries six times as much energy as water at the same tempera• ture. When steam condenses on the surface of cold food, it de• livers this latent energy to the food. If the pressure inside the steamer compartment rises, the steam can reach higher temperatures and deliver more energy to the food. This is the mechanism behind pressurized steamers, which may cook food up to twice as fast as pressureless (or atmos• pheric) steamers. As with baking, a layer of insulating vapour can form around food in a still steamer cavity. The natural convection inside the cavity tends to strip away this insulating layer of air, but it has a limited ability to do so. If food is tightly packed, or if the steamer is fully loaded with pans, convection is impeded and cooking slows down. The last few years have seen the addition of a fan to some steamers. Forced convection in a steamer has the same effect as it does in a convection oven, namely stripping away the insulating layer of vapour around food to speed cook• ing and provide even heat throughout the steamer cavity. Compartment steamers are often preheated once in the morning and left on throughout the day between uses,

8.3 TYPES OF COMPARTMENT STEAMERS There are two basic categories of steamers on the market, pres• sureless (atmospheric) and pressurized. Each type is available in gas, electric and direct steam connect models.

8.3.1 Atmospheric Steamer Atmospheric steamers are also referred to as "pressureless" steamers. The cavity is generally larger than that of a pressur• ized steamer, and the door is generally simpler. Atmospheric steamers are simpler to load, with no need to crank a door open and shut. The door may be safely opened at any point during the cook cycle to check on the food. Many atmospheric steamers employ a fan for forced convection steaming, to produce short cook times and even cooking throughout the compartment under full-load conditions.

Technology Review of Commercial Foodservice Equipment Volume H, Page 8-2 8.3.2 Pressurized Steamer Pressurized steamers are identifiable by their smaller compart• ments and heavy doors. Although these steamers cook smaller batches than pressureless steamers, cook times may be dramati• cally shorter depending on the food. Low-pressure steamers typically operate at 35 kPa (5 psi) pres• sure. These are high-volume steamers that are often used in schools and hospitals. High-pressure steamers have generally smaller compartments and operate at 70-105 kPa (10-15psi). Although they hold less food, they may cook up to twice as fast as a low pressure steamer. More precise timing is required as food cannot be checked while it is cooking, and because with faster cook times there is less room for error in removing the food before it be• comes overcooked.

8.3.3 Advanced Compartment Steamer Technologies FIGURE 8-2 8.3.3.1 Convection. Turbulent steam strips away the insulating Two-Compartment Pressure layer next to the food, for faster cooking that is more even Steamer- Direct Connected. Photo: Market Forge Company® throughout the cavity. There are two basic methods of produc• ing this forced convection. Some manufacturers inject steam into the cavity through jets in the cavity wall, others use a fan. 8.3.3.2 Standby. Some manufacturers maintain a steam gen• erator stand-by temperature just below boiling. This allows the appliance to produce steam 10-30 seconds after the steamer is loaded. This is a practical alternative to turning the steamer off between uses and incurring a 5-15 minute preheat, or using more energy to keep the entire cavity warm with circulating steam between uses. Cook times are a few minutes longer than if the steamer had been held at full input, as the cavity also ab• sorbs heat. The increase in cook time depends on when the steamer was last used (leaving residual heat in the walls of the cavity.) 8.3.3.3 Open Boiler. Another approach to steamer design uses an open well in the bottom of the steamer cavity instead of a traditional boiler. This mitigates some of the difficulties associ• ated with boiler maintenance, and allows easier access for cleaning.

8.4 CONTROLS Steamer controls are generally simple. There is usually a power switch and a timer, and there may be indicators to show readi• ness, steam pressure or water level. Steamers may also signal

Technology Review of Commercial Foodservice Equipment Volume II, Page 8-3 the need to maintain the boiler, and may automatically empty the boiler at the end of the day to reduce scale. Automatic timers on some steamers exhaust steam from the compartment at the end of the cook period, stopping the cooking process. This is especially useful for high pressure steamers, which cook rapidly and can overcook food easily. Some steamers use compensating timers, which automate de• frosting and cooking. As an example, suppose a load of frozen fish is cooked in a steamer with a compensating timer. Cavity temperature is monitored, and the timer does not begin to count down until the compartment nears 100°C (212°F), a temperature that corresponds to the frozen food having mostly thawed. At this point, the timer-preset with the desired cook time for a thawed food product-has "compensated" for the food's initial condition, whether it was frozen or thawed (as well as the cav• ity's initial condition, cold or preheated). In a pressure cooker, the drain valve would close at this point and pressurized cook• ing would begin.1

8.5 COMPARTMENT STEAMER PERFORMANCE An ASTM standard test method for steam cookers developed by PG&E allows manufacturers and users to gauge steamer pro• duction directly, and to evaluate steamer energy performance as well.12'3' The ASTM method reports several parameters of steamer per• formance, some of which are explained in the following sec• tions. The method evaluates energy efficiency under heavy-, medium- and light-loading conditions. Other factors that affect the actual performance of the steamer include ergonomics, ease of use and maintenance, and quality of construction.

8.5.1 Boiler Preheat Energy and Time Preheat energy and duration can be useful to food service opera• tors for managing power demands, and knowing how quickly the steam cooker can be ready for operation. Typical preheat times may vary between five and twenty min• utes, Table 8-1, which is enough to discourage most operators from turning the steamer off between loads. Some manufactur• ers have systems for maintaining cavity temperature between loads so that cooking can start immediately when the steamer is loaded. Otherwise the cook time may be several minutes longer because even if the boiler is maintained at full pressure between loads, the cool compartment walls are heated along with the food.[2]

Technology Review of Commercial Foodservice Equipment Volume II, Page 8-4 8.5.2 Boiler Idle Energy Rate Boiler idle energy rate is determined for the boiler while it is maintaining operating pressure or temperature when no cooking O is taking place. Idle energy rate (and pilot energy rate if appro• priate) is an important parameter for estimating energy con• sumption (Table 8-1) Gas steamers are far less efficient during idle than during cooking, due to the short cycles of the high- input burners.

TABLE 8-1 Maximum input rate, preheat and idle energy rate for compartment steamers121

Eled Elec2 Gas1 Gas 2

Measured Maximum Energy Input Rate 26.3 kW 19.1 kW 254 kBtu/h 199 kBtu/h Preheat Time: Heat-Up Time (min) 12.8 6.3 6.7 6.9 Fill Time (min) 4.2 0.5 3.9 3.6 Energy Consumption 5.3 kWh 1.0 kWh 28.1 kBtu 22.8 kBtu

Idle Energy Input Rate 1.3 kW 1.2 kW 16.8 kBtu/h 9.1 kBtu/h

8.5.3 Ice-Load Cooking Energy Efficiency Ice-load cooking energy efficiency is determined by "cooking" a capacity number of ice loads from -17°C to 82°C (0°F to 180°F). Ice load cooking energy efficiency (very similar to fro• zen vegetable cooking energy efficiencies) is a precise indicator of steam cooker energy performance under various loading conditions. This allows the food service operator to consider energy efficiency when selecting a steam cooker.[2]

8.5.4 Whole Potato Cooking Energy Efficiency Potato cooking energy efficiency is an indicator of steam cooker energy performance when cooking foods which require long cook times (e.g., potatoes, beans, rice, lasagna or casserole rethermalization). Whole potato cooking energy efficiency is determined by cooking the maximum capacity of fresh, whole potatoes to a specified doneness. The test demonstrates the dif-. ference in energy efficiency between pressure and pressureless steam cookers for this type of cooking event (see Figure 8-1). The information may help a food service operator to evaluate

Technology Review of Commercial Foodservice Equipment Volume II, Page 8-5 40

£ 35 ~) £■ 30 . c •S 25. E a Pressureless W 20 . g Pressurized $ 15 e « >o, e 2e 5J o ^ 0 Ice loads Potatoes

FIGURE 8­3 Efficiency of pressurized vs. atmospheric steaming in a gas compart­ ment steamer.

what type of steamer to select (pressure vs. pressureless vs. dual pressure mode) from an energy performance perspective.

8.1.1 Ice Load And Whole Potato Production Capacities Ice load and whole potato production capacities (lb(ice)/h or lb(potato)/h) are determined by the respective cooking energy efficiency tests. Ice load production capacity and potato pro­ duction capacity can be used by food service operators to choose a steam cooker to match their particular food output re­ quirements. Ice load production capacity is a close indicator of frozen vegetable production capacity (e.g., pounds of ice per hour is equivalent to pounds of frozen green beans per hour).'21

8.1.2 Water Consumption Water consumption (L/h) is monitored during both cooking en­ ergy efficiency tests to determine the rate of water usage. Water consumption characterization is useful for estimating water and sewerage costs associated with appliance operation.

8.1.3 Condensate Temperature

A. Condensate temperature is monitored during both cooking energy efficiency tests. Condensate temperature meas­ urement is useful to verify that the temperature does not exceed regional building code limits.

Technology Review of Commercial Foodservice Equipment Volume 11. Page 8­6 8.6 BENCHMARK ENERGY EFFICIENCY There is little published data on compartment steamer energy efficiencies. The estimated range of efficiencies for gas and electric steamers in Table 8-2 are based on data from the ratifi• o [3] cation of the PG&E test method , studies at the University of Minnesota'4, and personal experience of the authors.

TABLE 8-2 Cooking Energy Efficiency: Summary of Appliance Category (Average for atmospheric and pressureless) Gas Electric

Cooking Energy Efficiency {%) 30-40 60-80

'Average for atmospheric and prssureless steamers.

8.6.1 Full Load vs. Partial Load Efficiencies The ASTM method specifies different loading scenarios for heavy-, medium- and light-load tests. The results show a pre• dictable falling off of efficiency as the load size declines [Figure 8-2, Table 8-3]. This is largely due to the boiler. At full input, the boiler in the steamer labeled "Gasl" was working at close to 75% efficiency. However, in a real world cooking situation the boiler cycles on and off, and efficiency of the boiler at idle was only 26%. This translated into a cooking efficiency for the whole system (i.e., boiler and steamer) of 37% for a full load. When the boiler idled more often during cooking (i.e., in a light- load test) the efficiency of the steamer dropped to 25%. Obvi• ously, increasing the idle efficiency of the boiler is a major op• portunity to increase the overall efficiency of the gas compart• ment steamer.1 '

8.7 ENERGY CONSUMPTION Projected energy consumption for gas and electric compartment steamers are presented in Table 8-4 and 8-5. Based on PG&E's in-kitchen monitoring at its production test kitchen, average en• ergy consumption rates for compartment steamers reflect a duty cycle of 15% for gas units and 20% for electric units. " Daily energy consumption for steamers were calculated by multiply• ing the median rated energy input for each oven category by the respective duty cycle and the hours of operation. Duty cycle is

Technology Review of Commercial Foodservice Equipment Volume II. Page 8-7 g MoJiiittl EJMJ Q ljfKi IJUJ

FIGURE 8-4 Effect of loading on cooking energy efficiency in pressureless steam- ing'21

TABLE 8-3 Cooking Energy Efficiency, Production Capacity and Water Consumption (ice toad test-atmospheric steaming)121

Eled Elec2 Gas 1 Gas 2

Cooking Energy Efficiency (%)

Heavy Load 72 79 37 38

Medium Load 66 76 31 34

Light Load 53 66 25 27

Production Capacity (Ib/h) 129 155 156 111

Water Consumption Rate (gal/h) Heavy Load 64 68 64 5 Medium Load 34 64 34 7

Light Load 34 64 34 11

'Based on heavy load cooking scenario. 'Steamers use a flow of water to condense steam as it flows from the cavity to the drain hose. In most steamers this water flows continuously when the appliance is on. Gas2 used a solenoid linked to a thermocouple in the drain, so that cooling water flowed only when there was steam venting from the cavity (i.e. towards the end of the test when the ice in the pans had changed into hot water and was no longer con• densing all the steam that entered the cavity.)

Technology Review of Commercial Foodservice Equipment Volume II, Page 8-8 TABLE 8-4 o Projected Energy Consumption for Gas Compartment Steamers Nominal Rated Duty Avg. Energy Typical Annual Energy Size Energy Input Cycle Consumption Op. Hours Consumption a (kBtu/h) (%) (kBtu/h) (h/d) (kBtu)b

PRESSURIZED 2 Com p. 170-250 (Median) 210 15c 32 14 140,000

PRESSURELESS 2 Comp. 170-250 (Median) 210 15c 32 14 140,000

•Operating hours or appliance "on time" is the total period of time that an appliance is operated from the time it is turned "on" to the time it is turned "off'. bThe annual energy consumption calculation is based on the average energy use rate x the typical operating hours x 6 days per week x 52 weeks per year. The duty cycle is based on monitoring two gas convection steamers with input rates of 250 kBtu/h and 200 kBtu/h in a real-world production kitchen. An associated average energy consumption rate of 32 kBtu/h was calculated.'5'*'

TABLE 8-5 Projected Energy Consumption for Electric Compartment Steamers

Nominal Rated Duty Avg. Energy Typical Annual Energy Size Energy Input Cycle Consumption Op. Hours Consumption (kW) (%) (kW) {h/d)a (kWh)b (kBtu)c

PRESSURIZED 2 Comp. 36-48 d (Median) 42 12 14 21,800 74,500

PRESSURELESS 2 Comp. 18-36 (Median) 27 20" 14 21,800 74,500

"Operating hours or appliance "on time" is the total period of time that an appliance is operated from the time it is turned "on" to the time it is turned "off'. bThe annual energy consumption calculation is based on the average energy consumption rate x the typical operating hours x 6 days per week x 52 weeks per year. ■Conversion Factor: 1 kW= 3.413 kBtu/h dThe duty cycle is based on monitoring two steamers in a real-world operation1.781

Technology Review of Commercial Foodservice Equipment Volume II, Page 8-9 defined as the average rate of energy consumption expressed as a percentage of the rated energy input or the peak rate at which an appliance can use energy. Typical operating hours were gleaned from in-kitchen energy-use monitoring experiences and observations as well as on the PREP study191 and a proprietary end-use monitoring report. Projected annual energy consump• tion was determined by assuming a 6-day per week, 52-week per year operation.

8.8 VENTILATION REQUIREMENTS Compartment steamers are classified as light-duty from the per• spective of exhaust ventilation. For a side-wall canopy hood, the design ventilation rate for steam equipment would range from 75 to 100 L/s (150 to 200 cfm) per linear foot of hood.

8.9 RESEARCH NEEDS As discussed in Section 8.6, boiler idle-energy efficiency is one of the major factors in overall steamer efficiency. Improving the part-load efficiency of the boiler may be the most direct way to boost gas steamer performance. • Flue dampers. Gas fired boilers in compartment steamers often use heat exchanger tubes to carry flame through the body of the boiler. When the boiler is idling, these same tubes facilitate heat exchange out of the boiler and up the flue via naturally occurring convective air currents. Flue dampers may reduce these losses during idling. • Modulating, high-efficiency burners. Low cooking-energy efficiencies under part load conditions might be improved if the burners were designed to run efficiently at a lower input during idle, instead of toggling between zero and full input. • Insulation. The use of insulation around the cavity and the boiler should be reviewed to determine if amount or place• ment could to improve energy performance. • Windows. Evaluate the feasibility of an insulated window in the door of atmospheric steamers to reduce the heat loss associated with opening the door to check food during cooking.

Technology Review of Commercial Foodservice Equipment Volume II. Page 8-10 8.10 REFERENCES 1. Avery. A.C. 1980. A Modern Guide to Foodservice Equip• ment. CB1 Publishing Company, Inc. Boston. 2. Pacific Gas and Electric Company. 1995. Development and Validation of a Uniform Testing Procedure for Steam Cook• ers. Report 1022.95.19. 3. American Society for Testing and Materials. 1994. Standard Test Method for the Performance of Steam Cookers. ASTM F 1484-93, Annual book of ASTM Standards, Philadelphia 4. Snyder, O.P., Thompson, D.R. and Norwig, J.F., 1983. Comparative Gas/Electric Food Service Equipment Energy Consumption Ratio Study. University of Minnesota, March. 5. PG&E, 1990. "Cooking Appliance Performance Report: PG&E Production-Test Kitchen." PG&E Research and De• velopment Report No. 008.1-90.8, May. 6. PG&E. "Cleveland Model 42-CKGM-250 Gas Pressureless Compartment Steamer: Appliance Performance in Produc• tion." Publication Pending. 7. PG&E, 1991. "Production-Test Kitchen Appliance Perform• ance Report: Cleveland Electric Pressureless Steamer." PG&E Report No. 008.1-90.30 prepared for Research and Development, June. 8. PG&E. "Groen Model HY-6E HyperSteam Electric Pres• sureless Steamer Performance in Production." Publication Pending. 9. Claar, C.N., Mazzucchi, R.P., Heidell, J.A., 1985. "The Project on Restaurant Energy Performance (PREP) -End- Use Monitoring and Analysis." Prepared for the Office of Building Energy Research and Development, DOE, May.

Technology Review of Commercial Foodservice Equipment Volume II. Page 8-11 9. STEAM KETTLE o 9.1 INTRODUCTION Steam kettles are an improved version of the large stock pot used for range top cooking. And they are put to many of the same tasks. Steam kettles are often used to boil pasta, simmer sauces, stocks and stews. But steam kettles offer a huge increase in productivity, convenience and energy efficiency. As well, steam kettle cooking can be partially automated and closely controlled, far more so than cooking on a range top. Steam kettles are defined by their steam jacket, which may ex• tend half, two thirds, or the full distance from the bottom of the kettle to the rim. The circulation of steam inside the jacket in• sures that the kettle heats evenly, and the maximum temperature of the kettle is determined by the pressure of the steam, which may be from 7 kPa to 345 kPa (1 psi to 50 psi).

9.2 COOKING PROCESS FIGURE 9-1 Tabtetop mounted tilting self- Steam kettles cook by conduction: heat passes directly from the contained steam kettle. wall of the kettle into the food. This is the most common mode Photo: Groen/A Dover Industries of use for tasks like boiling and simmering. Depending on the Company pressure of the steam in the jacket, the maximum temperature of the kettle may be 100°C-148°C (212°F-298°F). At higher tem• peratures, kettles may be used for roasting and browning meat. With the addition of mesh baskets, the kettle may be used as a steamer. Some kettles have additional connections to the jacket for cold water, which allows the kettle to cook food and then chill it. Because kettles heat evenly, they need less supervision than a pot on the stove. A variety of controls allow the cooking process to be further simplified and automated. Manufacturers offer de• vices to measure the amount of water flowing into the kettle, timers to start cooking unattended and signal the end of the cook time, automatic valves to control cooking and chilling and mixers to eliminate the need to check or stir the food. Operators also use steam kettles for heating food up (e.g., rethermalizing precooked food and heating prepared sauces), for steaming foods like rice, boiling bagels and spaghetti, and for simmering long-cooking items such as chili. Cooking events may last from a few minutes to several hours, and take place at temperatures from 70°C to 150°C (150°F to 300°F).

Technology Review of Commercial Foodservice Equipment Volume II, Page 9-1 9.3 TYPES OF KETTLES Manufacturers offer a variety of steam kettles for commercial food service: direct steam and self-contained; tilting and sta• tionary; floor, wall and countertop mounted. All are available in gas and electric models. Capacity ranges from one liter to 760 liters (1 quart to 200 gal• lons). The source of steam may be a boiler built into the housing or base of a "self contained" type kettle, or for "direct steam connect" type kettles, an external steam supply. Many smaller capacity (i.e. less than 230 L (60 gal)) steam kettles are mounted on pivots so that they may be tilted for pouring. Some manufac• turers offer accessories such as timers and mixer attachments to automate steam kettle cooking. Kettles may be mounted on the wall, on a cabinet-, pedestal- or open-style base or on a counter- top.

9.3.1 Direct Steam Kettles In all kettles, steam enters the jacket and condenses on the kettle wall, transferring heat into the kettle and condensing back into water. The source of steam varies. Direct steam kettles are supplied with steam from an external boiler. While this makes the design of the kettle itself simpler, it incurs some additional maintenance. The kettle may need to be "blown down" once a day or more to eliminate condensate build-up in the steam sup• ply line. This process is usually manual, although some kettles offer systems that take care of the condensate automatically.

9.3.2 Self-Contained Kettles Self-contained kettles have a closed steam system. The jacket is filled with distilled water and steam is supplied by a gas or electric boiler contained in a housing on the kettle's stand. This complicates design and increases the price of the kettle, but makes steam kettles available to kitchens of any size and with any configuration of gas and electrical plumbing. Maintenance of the steam jacket is simple. There is generally a sight glass to inspect water level, and the jacket occasionally requires manual venting or refilling.

9.3.3 Tilting and Stationary Kettles Tilting kettles simplify the task of decanting a large volume of food from a deep kettle. Tilting kettles range in size up to 380 L (100 gal), and are available in all configurations of steam source and mounting style. The kettle is generally tilted with a hand-

Technology Review of Commercial Foodservice Equipment Volume II, Page 9-2 operated wheel, but in some cases an electric motor is used. The kettle is counterbalanced so that it may stop and remain in any position as it tilts. Tilting kettles are also provided with a pour• ing lip to guide the food into steamer pans or other serving o dishes. Additionally, they may have a tangent draw off valve at the bottom of the kettle. This allows foods such as spaghetti to be drained before decanting. Stationary kettles do not tilt, but are usually equipped with a draw-off tangent valve at the bottom of the kettle. The largest steam kettles, those between 380 and 760 L (100 and 200 gal) capacity, are available only as stationary models.

9.3.4 Mounting Style Smaller steam kettles, generally less than 40 L (10 gal)capacity, may be available in countertop models. Countertop kettles are available in gas heated, electric heated and direct steam configu• rations, and are generally tilting type kettles. Wall mounted kettles may be stationary or mounted on trun• nions for tilting. They are generally direct steam kettles, and are often installed as part of a battery of appliances. Kettles of 1- 400 L (0.25-100 gal) capacity are available in wall mounted configurations. Floor mounted models may be from 40-800 L (10-200 gal), di• rect or self contained, tilting or stationary. The kettle may be mounted on a pedestal or on an open or cabinet-style base.

9.4 ADVANCED STEAM KETTLE TECHNOLOGY In the last year two innovative steam kettle designs have emerged.

9.4.1 Insulated Steam Kettles One manufacturer has introduced a line of insulated steam ket• tles. The insulated jacket will reduce heat losses from the bot• tom and sides of the kettle, which in turn increases efficiency, lowers energy consumption and reduces heat flow into the kitchen.

9.4.2 Thermal Fluid Kettles This type of kettle circulates a thermal fluid through the jacket instead of steam. This increases the temperature range of kettles significantly; the manufacturer reports cooking temperatures of

Technology Review of Commercial Foodservice Equipment Volume II. Page 9-3 up to 182°C (360°F). This may make it possible to cook new items such as braised meats in a steam kettle. o 9.5 CONTROLS Steam kettle controls are generally simple, consisting typically of a power switch and a temperature dial. Smaller kettles may use thermostats to control cycling, while larger kettles use a pressure sensor in the jacket. Some manufacturers offer optional lines of accessories includ• ing electronic controls that start and stop kettle cooking and/or chilling operations automatically. Systems are also available to automate boiler maintenance operations.

9.6 STEAM KETTLE PERFORMANCE There is little published data for this category of appliances. An ASTM standard test method for steam cookers is under devel• opment at PG&E. When completed it will allow manufacturers and users to gauge steam kettle production directly, and to evaluate steam kettle energy performance as well. The ASTM method reports several parameters of steamer per• formance including maximum input rate, production capacity, cooking energy efficiency and rate of energy use while simmer• ! ing. Other factors that affect the actual performance of the steamer include ergonomics, ease of use and maintenance, and quality of construction.

9.6.1 Maximum Energy Input Rate Maximum energy input rate is determined for kettles while the controls are set for maximum heating and the burners are on, Maximum input rate can be useful to food service operators for managing power demands and estimating a kettle's energy cost.

9.6.2 Production Capacity Production capacity is determined during a heatup test that brings water from 20°C to 70°C (70°F to 160°F). It is a close indicator of how fast the kettle can bring soups, sauces, or other liquids up to temperature. Production capacity can be used by food service operators to choose a steam kettle to match their particular food output requirements.

Technology Review of Commercial Foodservice Equipment Volume II, Page 9-4 9.6.3 Heatup Energy Efficiency The heatup test is used to determine both production capacity and efficiency of the steam kettle. Efficiency of the steam kettle during heat up enables the food service operator to consider en• O ergy performance when choosing a steam kettle.

9.6.4 Simmer Energy Rate The simmer test determines the energy rate while simmering foods. Simmer rate is an indicator of kettle performance while cooking foods that demand long cook times, such as soups and chili. This information also allows the food service operator to consider energy performance when choosing a steam kettle. Table 9-1 presents performance characteristics for three differ• ent kettles based on data generated by PG&E from its develop• ment of the ASTM standard for kettles.

TABLE 9-1 Sfeam Kettle Performance Comparison Based on Preliminary Data for Three Steam Kettles111 Elec 10 Gas 10 Gas 40

Maximum Energy Input Rate (kBtu) 35 55 203 Heatup Energy Efficiency (%) 87 39 54 Production Capacity (gal/h) 41 29 131 Simmer Energy Rate (kBtu/h) 3 7 9

Note: Electric 10 and Gas 10 are a matched pair of 40 L (10 gal) tilting, tabletop ket• tles. Gas 40 is a tilting 150 L (40 gal) kettle.

The heatup energy efficiencies in Table 9-1 are derived from a period when the burners or elements of the steam kettle boiler are at full input and have been running for several minutes. At this point any significant work of heating the kettle system has been done; most of the energy is going into the water inside the boiler. Therefore heatup efficiency is a close indicator of boiler efficiency. Gas 10's lower efficiency, 39% vs. 54%, is probably not due to a smaller kettle or more surface area to volume, but a less efficient boiler design. Operating within "spec", Gas 10's exhaust temperature was over 425°C (800°F).

J

Technology Review of Commercial Foodservice Equipment Volume II, Page 9-5 9.7 BENCHMARK ENERGY EFFICIENCY Benchmark energy efficiencies for steam kettles are based the personal experience of the authors from work associated with test method development for steam kettles at PG&E,1'1 and on o 23 data fromth e University of Minnesota.'

TABLE 9-2 Benchmark Steam Kettle Cooking Energy Efficiency

Gas Electric

Cooking Energy 40 - 60 80 - 95 Efficiency (%)

9.8 STEAM KETTLE ENERGY CONSUMPTION Projected energy consumption for gas and electric steam kettles are presented in Table 9-3 and Table 9-4. The information is based on test method development work for steam kettles at PG&E, on data from the University of Minnesota Study[2], and from an unpublished proprietary end-use monitoring study. Daily energy consumption for kettles was calculated by multi• plying the median rated energy input for each kettle type by the respective duty cycle and the hours of operation. The duty cycle for the gas kettle is based on data from proprietary end-use monitoring reports; the duty cycle for the electric kettle is based on an energy consumption ratio of 1.8 for tilting skillets and assumes that kettles and skillets have similar energy use pat• terns. The duty cycle is defined as the average rate of energy consumption expressed as a percentage of the rated energy input or the peak rate at which an appliance can use energy. Typical operating hours were gleaned from the PR£P study. The pro• jected annual energy consumption was determined by assuming a 6-day per week, 52-week per year operation.

9.9 VENTILATION REQUIREMENTS Steam kettles are classified as light-duty from the perspective of exhaust ventilation. For a wall-mounted canopy hood, the de• sign ventilation rate for steam equipment would range from (75 to 100 L/s (150 to 200 cfm) per linear foot of hood.

Technology Review of Commercial Foodservice Equipment Volume II, Page 9-6 TABLE 9-3 Projected Energy Consumption for Gas Steam Kettle Nominal Rated Energy Duty Avg. Energy Typical Annual Energy Size Input Cycle Consumption Op. Hours Consumption a b (kBtu/h) (%) (kBtu/h) (h/d) (kBtu) Steam Kettle 10-100 gal 50 -125 (Median) 60 125 40c 50 4 62,400

"Operating hours or appliance "on time" is the total period of time that an appliance is operated from the time it is turned "on" to the time it is turned "off". bThe annual energy consumption calculation is based on the average energy consumption rate x the typical operating hours x 6 days per week x 52 weeks per year. cThe duty cycle of 40% is based on data from unpublished proprietary end-use monitoring studies An associated average energy consumption rate of 50 kBtu h was calculated.

TABLE 9-4 Projected Energy Consumption for Electric Steam Kettle Nominal Rated Duty Avg. En. Typical Annual Energy Size En. Input Cycle Consum. Op .Hrs. Consumption (wxd) (kW) (%) (kW) (h/d)a (kWh)b (kBtu)c

Steam Kettle 10-100 gal 6-36 (Median) 60 21 40° 9,980 34,000

"Operating hours or appliance "on time" is the total period of time that an appliance is operated from the time it is turned "on" to the time it is turned "off. ''The annual energy consumption calculation is based on the average energy consumption rate x the typical operating hours x 6 days per week x 52 weeks per year. 'Conversion Factor: 1 kW = 3.413 kBtu/h. ''The duty cycle of 40% is based on an energ\ consumption ratio of 1.8 for tilting skillets with an assumption that energy usage is similar for the two appliance types. An associated average energy consumption rate of 8 kW was calculated.

Technology Review of Commercial Foodservice Equipment Volume II. Page 9-7 9.10 RESEARCH NEEDS Consideration for R&D projects include: • Evaluate the benefit of upgraded kettle insulation. • Development/application of high-efficiency boilers. • Evaluate thermal fluid kettle.

9.11 GAS INDUSTRY MARKET Focus • Support benchmarking of steam kettle energy efficiency. • Encourage the use of lids for steam kettles (60% simmer energy use reduction).

9.12 REFERENCES 1. Unpublished experience of authors from developing and applying the standard test method to three steam kettles. 2. Snyder, O.P., and J.F. Norwig. March 1983. "Comparative Gas/Electric Food Service Equipment Energy Consumption Ratio Study. University of Minnesota. 3. Claar, C.N., Mazzucchi, R.P., Heidell, J.A., 1985. "The Project on Restaurant Energy Performance (PREP) -End- Use Monitoring and Analysis." Prepared for the Office of Building Energy Research and Development, DOE, May,

Technology Review of Commercial Foodservice Equipment Volume II, Page 9-8 o 10. BRAISING PANS

FIGURE 10-1 A 150 liter tilting braising pan. Photo Groen Inc.

10.1 INTRODUCTION Braising pans, also known as tilting skillets or tilting frying pans, are among the most versatile appliances found in the commercial kitchen. They are used to braise, saute, broil, roast, boil, fry, griddle, proof, hold, simmer and steam. In appearance, a braising pan resembles a flat-bottomed kettle. In practice, it combines the characteristics of a steam kettle and a griddle. The cooking surface is like a griddle plate, heated from beneath by atmospheric gas burners or electric elements. But this "griddle" plate has walls on all four sides so as to form a shallow rectangular pan. Energy input ranges from 6 to 18 kW for electric appliances and 6 to 120 kBtu/h for gas units. Ca• pacities vary from 38-190 liter (10-50 gallon). The appliance is commonly freestanding, on an open frame of tubular steel, or on a cabinet-style base. It may also be wall- mounted on trunnions, or equipped with casters. Smaller models come in tabletop configurations. Since they are often used for simmering, braising pans are typically equipped with a lid, which is usually mounted on the frame and counterbalanced.

Technology Review of Commercial Foodservice Equipment Volume II, Page 10-1 One characteristic feature of braising pans is the ability to tilt forward between 10° and 110° for pouring and cleaning. A lever or hand wheel, or more rarely an electric motor, brings the pan forward and holds it in a tilted position. A safety switch cuts off power to the burner or elements when the tilt exceeds a certain angle. Some cooking is done at a slight incline: grease from ba• con and ground beef can be drained as it forms. The front rim of the pan has a lip to guide food into serving pans when the skillet is tilted for pouring, and a common feature of many tilting skillets is a rack positioned to hold steam table trays just below this spout for filling. Some braising pans are also equipped with a draw-off valve, so that food can be de• canted from the bottom of the pan while it is horizontal. FIGURE 10-2 The braising pan can provide commercial kitchens with savings A 40 L (10 gal) countertop skillet. in time, money and line space by doing the job of several differ• The size of a tilting skillet affects en• ergy use directly and indirectly. As ent appliances. Throughout the day, the braising pan may pro• the amount of surface area relative vide extra griddle space for breakfast or lunch; be used as a ket• to volume increases, radiant losses tle to prepare rice or pasta; be rolled to the serving line and used from the appliance grow and effi• ciency declines. as a holding cabinet; be fitted with steamer baskets to prepare A skillet that is the right size for the vegetables or rethermalize frozen food, with a rack to wet-roast kitchen will be used more often. A meat, or with fry baskets to prepare French fried potatoes and study by PG&E at their production m other foods usually prepared in a deep fat fryer. test kitchen showed that the food- service staff began to use the brais- This appliance is particularly well suited to moving from one \ ing pan regularly only after a 32 gat- i Ion pan was replaced with a smaller mode of cooking to another. The procedure for making stew 18 gallon pan. provides a distinctive example. A cook can braise the meat in Photo: Groen the hot pan, allowing the juices to remain in the bottom. When the meat is cooked, he adds water, vegetables and spices into the pan. With the lid down, the stew is left to simmer for several hours. When it is done, the cook tilts the skillet to fill pans for the serving line and keeps the rest warm through mealtime.

10.2 BRAISING PAN PERFORMANCE There is very little data published on the performance of brais• ing pans. PG&E is developing an ASTM standard test method for brasing pans along side the kettle test method. When com• pleted it will allow manufacturers and users to gauge production directly, and to evaluate energy performance as well. Closely following the kettle standard, discussed in Section 9, the ASTM method for braising pans will report similar parame• ters including maximum input rate, production capacity, cook• ing energy efficiency and rate of energy use while simmering.

Technology Review of Commercial Foodservice Equipment Volume II, Page 10-2 10.3 BENCHMARK ENERGY EFFICIENCY Based on the personal experience of the authors from work as• sociated with the test method development and on data from the o University of Minnesota, J a range of energy efficiencies for both gas and electric skillets are presented in Table 10-1

TABLE 10-1 Braising Pan Cooking Energy Efficiency Gas Electric

Cooking Energy 30-50 80-95 Efficiency (%)

The Minnesota study compared two 68 L (18 gal) braising pans, one electric and one gas. They found a cooking efficiency of 52% for the gas braising pan vs. 79% for the electric. The gas pan heated water much faster than the electric pan, using 1.8 times more energy The gap between gas and electric performance should narrow as better technology is applied to gas tilting skillets. Most skillets in use now are older models that don't take advantage of stan• dard efficiency measures such as insulation or advanced burner design.

10.4 ENERGY CONSUMPTION Projected energy consumption for gas and electric braising pans are presented in Table 10-2 and Table 10-3. Daily energy con• sumption for braising pans was calculated by multiplying the median rated energy input for each skillet by its duty cycle and the hours of operation. The duty cycles are based on monitoring two gas and two electric tilting skillets in PG&E's production test kitchen.1 ] The duty cycle of an appliance is defined as the average rate of energy consumption expressed as a percentage of the rated energy input or the peak rate at which an appliance can use energy. Typical operating hours were gleaned from in- kitchen observations along with data from an unpublished pro• prietary end-use monitoring study. Projected annual energy con• sumption was determined by assuming a 6-day per week, 52- week per year operation.

Technology Review of Commercial Foodservice Equipment Volume 11, Page 10-3 TABLE 10-2 o Projected Energy Consumption for Gas Braising Pan Nominal Rated Energy Duty Avg. Energy Typical Annual Energy Size Input Cycle Consumption Op. Hours Consumption a b (kBtu/h) (%) (kBtu/h) (h/d) (kBtu)

Braising Pan 10-50 gal 60-120

(Median) 30 90 4SC 40 49,900

'Operating hours or appliance "on time" is the total period of time that an appliance is operated from the time it is turned "on" to the time it is turned "off'. bThe annual energy consumption calculation is based on the average energy consumption rate x the typical operating hours x 6 days per week x 52 weeks per year, cThe duty cycle is based on monitoring two gas braising pans with input rates of 85 kBtu/h and 62 kBtu/h in a real-world pro• duction kitchen (PG&E unpublished data). An associated average energy consumption rate of 40 kBtu/h was calculated.

TABLE 10-3 Projected Energy Consumption for Electric Braising Pan

Nominal Rated Duty Avg. En. Typical Annual Energy Size En. Input Cycle Consum. Op Hrs. Consumption a b c (wxd) (kW) (%) (kW) (h/d) (kWh) (kBtu)

Braising Pan 10-50 gal 6-18 (Median) 30 12 60d 7 4 8,730 29,800

'Operating hours or appliance "on time" is the total period of time that an appliance is operated from the time it is turned "on" to the time it is turned "off". bThe annual energy consumption calculation is based on the average energy consumption rate x the typical operating hours x 6 days per week x 52 weeks per year. 'Conversion Factor: 1 kW = 3.413 kBtu/h. dThe duty cycle is based on monitoring two electric tilting skillets with input rates of 9 kW and 11 kW in a real-world pro• duction kitchen.'1' An associated average energy consumption rate of 7 kW was calculated.

Technology Review of Commercial Foodservice Equipment Volume 11, Page 10-4 10.5 VENTILATION REQUIREMENTS Braising pans are classified as light-duty from the perspective of exhaust ventilation. For a wall-mounted canopy hood, the de• o sign ventilation rate for this equipment would range from 75 to 100 L/s (150 to 200 cfm) per linear foot of hood.

10.6 RESEARCH NEEDS

10.6.1 Atmospheric Burners All braising pans now on the market use atmospheric burners. These are the simplest and least expensive type of burner, and using them helps keep the initial cost of the appliance low. In studies on deep-fat fryers, well designed atmospheric burners are associated with cooking energy efficiencies that approach those of some fryers with more efficient infrared burners. How• ever, the same studies show that poorly designed atmospheric fryers have the lowest cooking efficiencies of any tested. Design of the burners and the heat transfer system can have a signifi• cant impact on appliance efficiency. One manufacturer of braising pans, Groen, uses a heat transfer system which incorporates heat exchanger fins on the bottom of the pan and an insulated combustion chamber. All of these are simple, reliable and inexpensive to implement with a relatively good increase in cooking efficiency.

10.6.2 Infrared Burners High efficiency infrared burners have not yet been applied to braising pans, but they have been associated with high overall efficiency in appliances such as fryers and griddles. Griddles using infrared burners show higher cooking efficiency than griddles using atmospheric combustion burners, and by analogy, a braising pan heated with infrared burners would enjoy a simi• lar increase in efficiency. Infrared burners would increase the purchase price of a new braising pan, but reduced energy con• sumption could offset the cost.

10.6.3 Thermal Fluid Lang, Inc. has developed a thermal fluid griddle in conjunction with GRI. This technology uses gas burners to heat oil, which is circulated through pipes to heat the griddle plate. It may prove more efficient to transfer heat into a thermal fluid than to use burners under the griddle plate. This systern also promises better temperature uniformity on the bottom of the pan, which would

Technology Review of Commercial Foodservice Equipment Volume II, Page 10-5 be an advantage for those operators who use the braising pan as a backup griddle.

10.6.4 Insulation Appliances like braising pans spend much of their duty cycle holding food at temperature, as in proofing and simmering. If the lid is open and the food is losing moisture freely, as much as half the energy into the appliance is working to evaporate water. Closing the lid can reduce energy use by 40% to 60%. With the lid down, the major energy loss from the appliance is radiant heat lost to the room. Insulation can reduce this loss, however it is rarely used in braising pans. Only one manufacturer, Legion Industries, Inc. makes a braising pan-the Skittle™-with insulated sides and under body. The outside of the pan is only warm to the touch when it is filled with 160°C (320°F) oil, indicating reduced radiant heat losses due to insulation. The manufacturer also offers a model with a tall, capsule lid that is fully insulated. FIGURE 10-3 The manufacturer contends their Skittle works well as a The revolutionary Skittle™ The only fully insulated braising pan steamer, utilizing gentle closed-cycle steaming and is just as fast manufactured in North America. The as convetional steamers, but with the added plus that there is no sides and bottom of the pan are insu boiler. As a griddle surface, it is as hot at the very edges as it is lated. The insulated "capsule" lid ^reates a large volume for steaming, in the center. It can also be used as a deep fat fryer; and when .holding and wet roasting. This model not it use, the capsule lid can be lowered to keep virtually all is electric; a gas model is under de• heat from warming up the kitchen because of its insulation. velopment. Shown with racks and pans for steaming. A fully insulated pan with an insulated lid, combined with the Photo: Legion Industries insulated burner chamber that Groen uses, would greatly reduce radiant losses from the pan. Considering that braising pans do much of their cooking in boiling or simmering mode, this would result in lower energy costs and less heat into the kitchen.

10.7 GAS INDUSTRY MARKET FOCUS • Support benchmarking of braising pan energy efficiency. • Support development of advanced burner options for gas braising pans. • Encourage insultating pan body and lid.

10.8 REFERENCES 1. PG&E, 1990. "Cooking Appliance Performance Report- Production Test Kitchen." PG&E Research and Develop• ment Report No. 008.1-90.8, Section 10, May.

Technology Review of Commercial Foodservice Equipment Volume II, Page 10-6 Snyder, O.P., and Norwig, J.F. March 1983. "Comparative Gas/Electric Food Service Equipment Energy Consumption Ratio Study". University of Minnesota. Legion Industries, Inc., Pennsylvania. "The Legion Line", Newsletter, Special Edition, Vol. 1 No. 5.

Technology Review of Commercial Foodservice Equipment Volume II, Page 10-7 11. BIBLIOGRAPHY

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Technology Review of Commercial Foodservice Equipment Volume II, Page 11-2 Gas Research Institute, "Advanced Residential and Light Commercial Cooktop Burner: a GRI Field Test Status Re• port." Gaz de France, Gas Utilization Research Centre, Research o and Development Division CERUG Activities Report, pp.24, 1992. Giammer, R.D., D.W., Locklin, S.G., Talbert, Preliminary Study of Ventilation Requirements for Commercial Kitch• ens, ASHRAE Journal. 1971. Gordon, E., and D.J. Horton, D, If You Can't Stand the heat, Get IT Out of the Kitchen. Cooking for Profit. May, 1995. Gordon, E., V. Kam, and F., Parvin, Topical Paper: Emis• sions from Commercial Cooking Operations and Methods for Their Determination, prepared for the American Gas As• sociation Laboratories, December, 1994. Hildemann, L.M., D.B. Kilnedinst, G.R. Casset, et.al., Sources of Urban Contemporary Carbon Aerosol, Environ. Sci. Technol.. Vol. 28, NO. 9, 1994. Himmel, R.L. and RE. Stack, Application of Intermittent Ignition Devices to Commercial Cooking Equipment, pre• pared by American Gas Association Laboratories for the Gas Research Institute, GRI-78/0050, October, 1981. Himmel, R.L. and RE. Stack, Commercial Cooking Equip• ment Improvement, Volume I: Range Ovens, prepared by American Gas Association Laboratories for the Gas Re• search Institute, GRI-80/0079.1, October, 1981. Himmel, R.L. and R.E. Stack, Commercial Cooking Equip• ment Improvement, Volume II: Deep Fat Fryers, prepared by American Gas Association Laboratories report for the Gas Research Institute, GRI-80/0079.2, October, 1981. Marbek Resource Consultants Ltd. and K.P. Engineering and Design, Strategic Market Assessment of the Commercial Cooking Sector, prepared for Consumers' Gas, January, 1987. New England Gas Association, Opportunities and Competi• tion in the Food Service Equipment Industry, presentation by R. Simek, Senior Consultant, Arthur D. Little, 1995. Pacific Gas and Electric Company, Appliance Performance in Production: Hobart Electric Char Broiler Model CBS I,

Technology Review of Commercial Foodservice Equipment Volume II, Page 11-3 Report No. 008.1-92-4, prepared by Food Service Technol• ogy Center, 1992. • Pacific Gas and Electric Company, Appliance Performance Report: Vulcan-Hart Electric Range, Model VR-4, Report 008.1-90.24, prepared by Food Service Technology Center, June, 1991. • Pacific Gas and Electric Company, Cooking Appliance Per• formance Report: PG&E Production-Test Kitchen, Report No. 008.1-90.8, prepared by Food Service Technology Center, May, 1990. • Pacific Gas and Electric Company, Custom Electronics En• ergy Saver Gas Control System for Commercial Broilers, Report No. 5011.95.27, prepared by Food Service Technol• ogy Center, 1995. • Pacific Gas and Electric Company, Dean Decathalon ™-35 Gas Fryer Performance Report, Report 008.1-91.8 prepared by Food Service Technology Center, 1991. • Pacific Gas and Electric Company, Development and Appli• cation of a Uniform Testing Procedure for Griddles, Report 008.1-89.2, prepared for Research and Development, San Ramon, California 1989. • Pacific Gas and Electric Company, Development and Appli• cation of a Uniform Testing Procedure for Open, Deep-fat Fryers. Report 008.1-90.22, prepared for Research and De• velopment, San Ramon, California, 1989. • PG&E, Development and Validation of a Uniform Testing Procedure for Ovens, Report 1-22.95.20, prepared for Re• search and Development, San Ramon, California October, 1995. • Pacific Gas and Electric Company, Development and Vali• dation of a Uniform Testing Procedure for Range Tops Re• port 1-22.95.20, prepared for Research and Development, San Ramon, California October, 1995. • Pacific Gas and Electric Company (PG&E), Development and Validation of a Uniform Testing Procedure for Steam Cookers, Report 1022.95.19, prepared for Research and De• velopment, San Ramon, California, 1995. • Pacific Gas and Electric Company, Frying Medium Qualify Life Determination, Report 008.1-90.20 prepared by Food Service Technology Center, 1990.

Technology Review of Commercial Foodservice Equipment Volume n, Page 11-4 • Pacific Gas and Electric Company, Frymaster®Model MJH50 Gas Fryer Performance Report, Report 008.1 -91.5 prepared by Food Service Technology Center, 1991. o • Pacific Gas and Electric Company, In-Kitchen Frying Me• dium Life Study, Report 008.1-92.16 prepared by Food Service Technology Center, 1993. • Pacific Gas and Electric Company, Keating MIRACLEAN Model 36 x 30IBLD Gas Griddle: Application of ASTM Standard Test Method, Report 5017.93.3, prepared by Food Service Technology Center, 1993. • Pacific Gas and Electric Company, Montague Model VI36-5 Heavy-Duty Open Top Gas Range: Appliance Performance in Production, PG&E Report 5011.93.7, prepared by Food Service Technology Center, December, 1993. • Pacific Gas and Electric Company, Montague Model V136-5 Heavy-Duty 30,000 Btu/h Open Top Gas Range: Applica• tion of ASTM Standard Test Method F1521-94, prepared by Food Service Technology Center, October, 1995. • Pacific Gas and Electric Company, Pitco Frialator® Model El4 Electric Fryer Performance Report, Report 008.1-91.7 prepared by Food Service Technology Center, 1991, • Pacific Gas and Electric Company, ToastmasterModel RA36C1: Electric Range Performance Report, Report 008.1-92.10, prepared by Food Service Technology Center, September, 1992. • Pacific Gas and Electric Company, U.S. Range Model RGTA-2436-1 Gas Griddle: Application of ASTM Standard Test Method. Report 5017.93.1, prepared by Food Service Technology Center, 1991. • Pacific Gas and Electric Company, Vulcan-HartFrycat™ Model CCFD-2 Gas Fryer Performance Report, Report 008.1-91.6, prepared by Food Service Technology Center, 1991. • Pacific Gas and Electric Company, Wells Model B-50 Elec• tric Broiler: Appliance Performance in Production, Report No. 5011.94.3, prepared by Food Service Technology Cen• ter, 1994. • Pacific Gas and Electric Company, Wolf Commander Range- Match SUPER Char-Broiler: Appliance Performance in Production, Report No. 008.1-91-28, prepared by Food Service Technology Center, 1993.

Technology Review of Commercial Foodservice Equipment Volume H, Page 11-5 • "Profit by Conserving Energy in Your Restaurant", A pub• lication of the Buildings Energy Technology Transfer Pro• gram, Energy Mines and Resources Canada, ISBN 0-622- 13223-8, 1984. • ProTech Publishing and Communications (New Albany, IN), "New Technology Ovens at Work", Pizza Today.. Vol. 13, Number 8, August, 1995. • Raloff, J., "Cholesterol: Up in Smoke; Cooking Meat Dirties the Air More Than Most People Realize", Science News. Vol. 140, July, 1991. • Scriven, C. and J. Stevens, Food Equipment Facts: A Hand• book for the Foodservice Industry". Van J. Reinhold (NY), Revised Edition, 1989. • Smith, V.A., R.T. Swierczyna, and C.N. Claar, "Application and Enhancement of the Standard Test Method for the Per• formance of Commercial Kitchen Ventilation Systems." ASHRAE Transactions. V. 101, Pt. 2, 1995. • Soling, S.P., and J.Knapp, "Laboratory Design of Energy Efficient Exhaust Hoods", ASHRAE Transactions. 1985. • Stack, R.E., "Application of Pulse Combustion to Closed Top Commercial Cooking Equipment". American Gas As• sociation Laboratories report to the Gas Research Institute, GRI-88/0300, August, 1988. • Talbert, S.G., L.B. Flanigan, J.A. Fibling, "An Experimental Study of Ventilation Requirements of Commercial Electric Kitchens". ASHRAE Transactions. 1973. • UL. [Underwriters laboratories, Northbrook, IL.], Standard for Safety Exhaust Hoods for Commercial Cooking Equip• ment, Standard 710-90, 4th edition, 1990. • University of Manitoba, Increasing Profits by Using Energy Efficient Food Preparation Equipment, Processes and Pro• cedures, prepared by Office of Industrial Research, Depart• ment of Mechanical Engineering for the BETT Program Restaurant Sector, Second Draft, March, 1985. • University of Manitoba, Hie Better Restaurant Kitchen: An Analysis of the Energy Usage and Conservation Potential for Restaurant Food Preparation Equipment, Processes and Procedures, prepared by the Office of Industrial Research, Department of Mechanical Engineering, for the BETT Pro• gram - Restaurant Sector, September, 1984. • ASTM Standard Test Methods

Technology Review of Commercial Foodservice Equipment Volume n, Page 11-6 ASTM Standard Test Method for the Performance of Steam Cookers, Designation: F 1484-93. ASTM Standard Test Method for the Performance of Convec• tion Ovens, Designation: F 1496-93. ASTM Standard Test Method for the Performance of Range Tops, Designation: F 1521-94. ASTM Standard Test Method for the Performance of Grid• dles, Designation: F 1275-95. ASTM Standard Test Method for the Performance of Open Deep-Fat Fryers, Designation: F 1361-95. ASTM Standard Test Method for the Performance of Dou• ble-Sided Griddles, Designation: F 1605-95. ASTM Standard Test Method for the Performance of Com• bination Ovens, Designation: F 1639-96. ASTM Standard Test Method for the Performance of Ex• haust Ventilation Systems (Energy Balance Protocol). Pub• lication pending. 1995.

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