Table of Contents

Introduction ...... 1 Major Seminar Topics ...... 1

Issues for Refrigeration Facilities ...... 3 Users of Refrigeration ...... 3 Refrigeration Classifications ...... 4 Typical Supermarket Electrical Usage ...... 5 Typical Commercial and Industrial Electrical Usage ...... 5 Integrated Demand Side Management (IDSM) ...... 6 What is Title 24?...... 22 Reasons for Using Refrigeration ...... 23 Refrigeration Units in California ...... 27 Benefits of Refrigeration ...... 27 AHRI Standard 1200 ...... 28

Fundamentals of Refrigeration ...... 39 A Few Terms and Concepts ...... 39 Refrigeration Basics ...... 40 Vapor Compression System ...... 43 Refrigeration System Divided Into Two Parts ...... 49 Refrigeration Cycle ...... 50 A Conventional Refrigeration System ...... 53 Parallel or Multiplex Refrigeration System ...... 54 It’s Only A Matter Of Size ...... 56 Sizing Multiple Compressors in Parallel Rack Systems ...... 57 Check Your Understanding ...... 58

Refrigeration System Components ...... 59 Compressor Design...... 60 Reciprocating Compressors ...... 62 Screw Compressors ...... 63 Scroll Compressors ...... 65 Compressor Summary ...... 70 Condensers and Heat Rejection Techniques ...... 73 Air-Cooled Condensers ...... 74 Water-Cooled Condensers ...... 75 Evaporative Condensers ...... 76 Condenser Efficiency ...... 78 Exercise: Condenser Financial Analysis ...... 83 Evaporators ...... 89 Evaporator Fan Controller for Walk-in Coolers ...... 92 Expansion Valves ...... 94

Refrigerants ...... 97 A Brief Chemistry Lesson...... 97 Refrigerant Chemical Composition ...... 98 Safety Classifications ...... 100

Efficient Technologies for Commercial Refrigeration i

Naming the Refrigerants ...... 101 Pure Refrigerants and Blends ...... 108 Glide ...... 109 Refrigerant Choices for Commercial Refrigeration ...... 111 Interim Refrigerant Alternatives ...... 112 R-22 Compared with R-404A and R-507 ...... 122 New Refrigerant: Hydrofluoroolefins (HFOs) ...... 123 Retrofit Options for Existing Systems ...... 124 Options for New Refrigeration Equipment ...... 128 Natural Refrigerants ...... 130 Indirect Refrigeration Systems ...... 131 Carbon Dioxide in Indirect Cascade Refrigeration Systems ...... 132

Refrigerant Management Program Rules ...... 135 Regulated Refrigerants ...... 139 Commercial Refrigerant Research Project (A Case In Point) ...... 140 Test Result Tables ...... 145 Refrigerant Tables ...... 146

Methods For Improving Refrigeration System Efficiency ...... 153 A Brief Physics Lesson...... 154 Condensate Flashing (Flash gas) or Incomplete Condensing ...... 161 Subcooling ...... 162 Floating Head Pressure ...... 169 How to Measure Floating Head Pressure and Condensing Temperature Difference...... 175 Floating Suction Pressure ...... 180 Heat Recovery System Design ...... 185 Check Your Understanding ...... 186 Energy Management Systems ...... 188 Demand Response ...... 192 How Refrigeration Facilities Can Reduce Energy Costs ...... 196 Small Factors in Design Efficiency ...... 197 Big Factors in Design Efficiency ...... 197 California’s Title 24 Energy Code ...... 199 What Is Zero Net Energy? ...... 204 Title 24 Compliance for Commercial Refrigeration ...... 206

ii Efficient Technologies for Commercial Refrigeration Speaker’s Bio, David M. Wylie, P.E. During the oil crisis of the early 1970’s, David was finishing engineering school at Cal Poly San Luis Obispo and subsequently achieved a Registered Professional Engineer License in California. Energy efficiency was getting more attention and an interest in cost analysis led David to completing an MBA at National University which provided him with even more tools to analyze energy efficiency investment from both a mechanical and financial perspective. David and his two partners began working together in 1976 and the Engineering Management Consulting firm of ASW (now ASWB Engineering), located in Tustin, California, today has a staff of over 25. The work experience covers the range of energy engineering including research, development, program design, measurement, feasibility study of electrical and mechanical systems, and energy supply for commercial and industrial facilities. David, who holds a college teaching credential, teaches what he does and knows about, and has developed over 20 courses that address energy-efficient systems. He has an ability to take sophisticated engineering concepts and relate them in a way you can understand, and the materials are presented in a friendly and practical way. Several of David’s articles have been published in trade magazines and he has written a book titled “New Refrigerants for Air Conditioning and Refrigeration Systems” that was published in 1996. ASW Engineering has received awards for innovations in engineering from the American Society of Heating, Refrigerating, and Air-Conditioning Engineers, Southern California Edison, and California’s Governor.

 ASWB Engineering January 2015

Prepared by: David M. Wylie, P.E. ASWB Engineering Tustin, California

Tel: (714) 731-8193 Fax: (714) 731-1921 Email: [email protected] Web site: www.aswb-engineering.com

Important:

These materials are meant to examine commercial refrigeration systems and energy efficiency issues. They are meant to clarify and illustrate typical situations and must be appropriately adapted to individual circumstances. Moreover, the materials are not intended to provide legal advice or establish legal standards of reasonable behavior.

Efficient Technologies for Commercial Refrigeration iii

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iv Efficient Technologies for Commercial Refrigeration

Introduction

Efficient Technologies for Commercial Refrigeration is a class that introduces elementary refrigeration concepts and various energy efficiency techniques and technologies that, when properly applied, can save on energy costs.

Refrigeration uses a significant amount of electricity on a year-round basis.  Refrigeration uses more kWh per ton of refrigeration than HVAC systems  Refrigeration makes up 5 to 8% of the commercial sector electrical end use in California  Many systems are old, operate inefficiently, and have few (if any) system improvements

Major Seminar Topics

In this seminar, we will discuss:  Issues for refrigerated facilities, including a description of users of refrigeration  Typical supermarket, commercial, and industrial electrical usage, and reasons for and benefits of refrigeration  Fundamentals of refrigeration, including vapor compression systems and the refrigeration cycle  Refrigeration system components  Refrigerants  An overview of ways refrigeration facilities can improve refrigeration system efficiency and reduce energy costs

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2 Efficient Technologies for Commercial Refrigeration Issues for Refrigeration Facilities

This section discusses the following topics:  Users of refrigeration including general classifications  Typical supermarket electrical usage  Typical commercial and industrial electrical usage  Reasons for using refrigeration  AHRI Standard 1200-2010  Integrated Demand Side Management Users of Refrigeration

Commercial business establishments that use refrigeration vary in size from small “mom-and-pop” convenience stores, to supermarkets of all sizes, to larger industrial and commercial applications.

Members of the broad category of “retail food stores,” which includes supermarkets, consume 85% of commercial refrigeration energy.

There are a wide variety of facilities and applications that use refrigeration to process, freeze, store, transport, prepare, and display perishable food products that are for sale.

Mechanical refrigeration is also used in comfort air conditioning and to process or manufacture almost every product or commodity on the market today.

Refrigeration has made possible many manufacturing industries, including the production of plastics, synthetic rubber, textiles, paper, and many other useful materials and products.

Efficient Technologies for Commercial Refrigeration 3 Refrigeration Classifications

Let’s take a look at the six general classifications typically used to describe the various uses of refrigeration.

Classification Typical Facilities and Uses Domestic refrigeration Includes your small home refrigerator and freezer, ranging in size from 1/20 to 1/2 horsepower. Commercial refrigeration Food Services Group I Grocery stores, small and large supermarkets, meat markets, delicatessens, food locker storage units Food Services Group II Restaurants, cafes, drug stores, taverns, cafeterias, dining rooms, carry-out vendors, stadium concession stands Beverage and Water Cooling Service stations, offices, employee break rooms, public buildings, recreational facilities, theaters, retail stores Institutions Hotels, hospitals, libraries, schools Industrial refrigeration Applications larger than commercial refrigeration; examples include ice plants, large food-packing plants, breweries, creameries, and industrial plants, such as oil refineries, chemical plants, rubber plants, etc. Cold Storage Products and applications such as flowers, medicine, candy, fresh fruit and vegetables, photo processing, morgues, laboratory supplies Agriculture Milk cooling, fresh vegetable storage, produce packing, meat and egg storage Marine and transportation Specialized commercial and industrial applications; Marine refrigeration refrigeration refers to ship-board refrigeration for fishing boats vessels transporting perishable cargo; transportation refrigeration applies to refrigerated trucks and railway cars Comfort air conditioning Applications for providing air conditioning for human comfort, including temperature and humidity control, air motion, and filtering Industrial air conditioning Applications that have a primary function other than to provide human comfort

Convenience Stores

Convenience stores range in size from 800 to 4,000 square feet, with the average store about 2,500 square feet. Many are open for business 24 hours per day, and others are open between 18 and 24 hours. For a “traditional” convenience store, about 14% of their operating expenses are for refrigeration. This percentage will vary depending on the location.

4 Efficient Technologies for Commercial Refrigeration Typical Supermarket Electrical Usage

The supermarket industry is a very competitive field.  Supermarkets operate at very thin profit margins—on average, profit margins are less than one percent, which is about the same as their average utility costs.  Supermarkets should be interested in finding ways to reduce their equipment energy costs. The most savings potential lies with the refrigeration systems.

Lighting 25%

Other Refrigeration 10% 50%

HVAC 15% Typical supermarket electrical usage Typical Commercial and Industrial Electrical Usage

In commercial and industrial refrigerated facilities, up to 30% or more of electrical use is consumed by refrigeration systems. The pie chart below shows electrical usage for a typical brewery where the brewing process operates 24 hours a day, seven days a week.

Refrigeration Lighting 30% 15%

Other Compressed 15% air Packaging 15% Water 5% CO2 collection pumping 10% 10%

Typical industrial facility electrical usage

Efficient Technologies for Commercial Refrigeration 5 Integrated Demand Side Management (IDSM)

Sustainable?

One objective of this class is to learn how we can maintain our momentum toward achieving a sustainable planet. Without a livable planet, there wouldn’t be any refrigeration systems to optimize!

There are many challenges when it comes to preserving the quality of the air, water, and land needed to sustain life on this planet, and many of these challenges involve the way we produce and use energy. Our success will rely on thousands of individuals making the decision to use energy in a smarter way at their facilities.

Compared to 20 years ago, today’s generation, distribution, and use of energy is more complex. The emergence of the smart grid and other advanced technologies have enabled new and innovative energy management strategies, providing us with more opportunities for system control.

Making smarter use of energy in our facilities means approaching energy from several perspectives, including efficiency, load management, and distributed generation, to name a few. These different perspectives may have interactive effects and warrant a more holistic approach to managing energy use.

This multi-faceted approach to energy demand management is known as IDSM (Integrated Demand Side Management).

6 Efficient Technologies for Commercial Refrigeration

As demonstrated in the graphic above, IDSM includes much more than the numerous categories of demand management strategies described within this course.

The vision of IDSM calls for us to look at facilities from a holistic perspective and manage the use of all our resources, including water. It challenges us to look forward, to continuously identify and adopt new strategies and advanced technologies as they become available, and to use every tool available to gain greater control over how and when our facilities use energy.

Implementing and integrating DSM strategies should become more and more feasible in the coming years. We are likely to see improved payback periods for IDSM investments, driven by increased affordability of equipment, rising energy costs, and the availability of financial incentives.

Improvements in IDSM feasibility and assistance with implementation will also be driven, in large part, by the ambitious emission reduction goals set out in recent years by government agencies. Widespread adoption of IDSM is vital to meeting these goals.

Efficient Technologies for Commercial Refrigeration 7 Supply vs. Demand Side Management

To best understand IDSM, it is important to distinguish demand side management (DSM) from its counterpart, supply side management (SSM).

Maintaining stability on the electricity grid requires supply and demand to be balanced. As electrical demand rises, grid operators compensate by bringing additional power generation online.

Meeting demand by adjusting the generation, transmission, and distribution of electricity is referred to as supply side management.

Demand side management works from the other side of the equation; it works to balance supply and demand by adjusting electrical load at the facilities that use electricity rather than the output of power plants.

From the perspective of grid operators, it is more effective to pay consumers to adjust the amount or timing of their electrical demand rather than relying on peak generation or building additional power plants.

A range of programs are available to support the implementation of DSM strategies.

Generation (supply) Load (demand)

8 Efficient Technologies for Commercial Refrigeration DSM Strategies

The graphic below provides an overview of the major categories of strategies that can be used to control the level or timing of electrical demand.

Electricity DSM refers to the redistribution of electricity load, such as shifting the load from one time period to another. This may be accomplished by means of load management or demand response, for example. Unlike demand reduction, DSM does not necessarily reduce the total energy consumed.

DSM can contribute to improving the efficiency of the electricity system, and can benefit the generation, transmission, and distribution networks. DSM can be implemented using renewable and low-carbon generation technologies.

There are many possible means for achieving energy management and DSM, including:  Energy audits  Enhanced facility design and processes  Energy efficient equipment  Energy conservation programs  and more

DSM also can refer to utility-sponsored programs that increase energy efficiency or the management of demand, including load management techniques.

Efficient Technologies for Commercial Refrigeration 9 Energy Efficiency (EE) and Energy Conservation (EC)

In today’s business environment, saving on energy costs is essential. Owners, managers, or operators of commercial and industrial facilities are always searching for ways to improve the efficiency of their operations. Facility management must consider energy efficiency and energy conservation as a business opportunities—ways to reduce energy costs, save money, and increase profit.

Throughout this course we will discuss various strategies of operation which include energy efficiency (EE) measures as well as energy conservation (EC).

Traditional energy efficiency (EE) measures involve reducing energy use without sacrificing the level of product, service, or output provided, and often entail replacing equipment or upgrading controls.

Energy conservation (EC) refers to reducing energy as well as the associated output, and can be as simple as turning off a light when it is not needed. EC strategies are typically behavioral in nature and involve conscious decisions to avoid energy waste.

10 Efficient Technologies for Commercial Refrigeration Distributed Generation (DG)

Distributed Generation (DG) is the generation of power at the location where it is used, and includes renewables such as wind, solar, energy storage such as batteries, as well as fuel-based generation including combined heat and power.

DG can be described as any technology that produces power, either outside or connected to the utility grid. DG devices are usually installed for an economic or system benefit that the distribution system or central generating plant cannot provide.

Use of small-scale renewables provides a direct benefit in reducing demand on the grid and as well as emissions from non-renewable sources.

Fuel-based onsite generation supports efficient energy use by avoiding losses associated with power distribution over long distances and, in the case of combined heat and power systems, allows more energy to be extracted from the fuel by recovering waste heat. Distributed generation technologies are often paired with energy storage (ST) technologies such as batteries.

DG applications can consist of:  Installations on utility company sites, such as sub-stations or power poles  Installations on the system or supply side of the meter at a customer site or other locations other than utility company sites  Installations on the customer side of the meter such as micro-cogeneration, standby generation, and self-generation

Efficient Technologies for Commercial Refrigeration 11 Controlling the Timing of Demand

In addition to reducing total energy consumption, we can use energy in a smarter way by controlling when it is used. We can adjust the timing of electrical demand at our facilities to take advantage of availability and price factors to the benefit of all. There are several types of strategies to help us achieve this.

Load Shifting (LS)

Load shifting (LS) strategies involve the shifting of electrical load from the peak hours to off-peak, when the cost of generating that electricity is much lower.

Businesses save money by taking advantage of the lower off-peak electricity rates. When this is performed automatically on a daily basis, it is called permanent load shifting (PLS). Storage (ST) technologies play an important role in many load shifting strategies, such as with thermal energy storage (TES). With TES, ice or chilled water is produced off-peak periods and used for cooling during on-peak periods.

Permanent Load Shifting (PLS) is type of load shifting, where on a recurring basis businesses agree to shift energy usage for cooling during the summer peak hours to off-peak hours. A few PLS technologies include thermal energy storage, batteries, and flywheels. Implementing these types of technologies can also allow businesses to qualify for grid operator incentive programs.

12 Efficient Technologies for Commercial Refrigeration Peak Management (PM)

Peak management (PM) strategies involve the reduction of energy use during on-peak hours, where equipment is controlled automatically to avoid peaks in the facility’s overall energy use. Peak Management is a category of DSM strategies that includes peak pricing, time-of-use (TOU) rates, and demand limiting.

Businesses save money by avoiding high demand charges, which make up a large portion of a facility’s energy bill. These strategies are also commonly referred to as “peak shaving” or “demand limiting.”

In order to avoid peak electrical demand at the facility, grid operators have to build capacity to serve maximum load. Energy peaks are often seen during summer months, when high temperatures drive greater air conditioning loads. To encourage less on-peak usage, energy suppliers charge time-of- use rates that vary with time of day, day of week, and season.

Efficient Technologies for Commercial Refrigeration 13 Demand Response (DR)

Demand response (DR) involves occasional and temporary reductions in facility electrical demand when a signal is received from the utility company or grid operator. Businesses receive financial incentives based on the amount of demand reduced.

DR events are temporary and can be as short as two hours. Events are called for various reasons, such as high electrical demand, spikes in electricity prices, or when power grid integrity may be at risk. Participating businesses are rewarded through installation incentives and energy bill reductions.

In a following section, we will discuss demand response in greater detail and highlight strategies that are commonly used for industrial facilities.

14 Efficient Technologies for Commercial Refrigeration Regulatory Goals

In 2014, the U.S. Environmental Protection Agency proposed a Clean Power Plan for the country, in which carbon emissions from the power sector are to be reduced by 30 percent from 2005 levels by the year 2030. As part of this plan, each state will be given specific goals based on their mix of emissions and power sources.

One state that has been pursuing energy efficiency for decades is California. In fact, California set similar targets for itself and wrote them into law several years before the EPA released its national plan.

In 2006, the California Air Resources Board passed Assembly Bill 32 (AB 32) — the first mandatory greenhouse gas reduction law in the United States.

A few of AB 32’s direct emission-reduction measures include promoting:  Energy efficiency  Combined heat and power  Reaching 33% renewable electricity

Through these strategies, AB-32 aims to reduce California’s emissions to:  1990 levels by 2020  80% below 1990 levels by the year 2050

Implementing IDSM

Rather than evaluating potential DSM strategies one at a time, businesses can elect to explore a range of potential strategies through a comprehensive IDSM evaluation.

With this approach, synergies between DSM strategies can be recognized, such as equipment or controls with the potential to enable multiple DSM strategies at little or no additional cost. For instance, an energy management system implemented for energy efficiency and conservation purposes could likely enable demand response and peak management as well. It is also inherently more efficient to perform a single comprehensive site inspection rather than several limited-scope inspections.

A major advantage of this approach is that it better empowers businesses to make informed decisions. By providing data on the estimated costs, benefits, and payback periods for various IDSM packages, businesses can confidently select the strategies that best suit their operations, preferences, and budget.

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16 Efficient Technologies for Commercial Refrigeration Benefits of IDSM

As efforts to implement IDSM progress, we will see multiple benefits to our electrical grid, environment, and society.

Widespread IDSM implementation will:  Enable grid operators to better forecast demand, enabling more efficient use of generation resources.  Reduce peak load on the grid, reducing reliance on peak generators.  Help avoid the need to construct new power plants.  Mitigate energy losses from transmitting electricity over long distances.  Expand the green energy economy, creating new jobs.  Overall, IDSM implementation will provide for a more cost-effective, flexible, sustainable, and resilient approach to meeting our energy needs. The reduction in emissions resulting from this approach will help us to minimize impacts to our air, water, and land.

Businesses who implement IDSM at their facilities can also benefit tangibly in several ways:  Save money on a year-round basis by permanently reducing energy consumption, implementing onsite generation, or shifting demand to off-peak periods with lower rates.  Additional cost savings in summer months by temporarily reducing demand when called by utility companies or grid operators (demand response).  Benefits to the health and comfort of facility occupants and productivity improvements resulting from better indoor air quality.

Efficient Technologies for Commercial Refrigeration 17 Example IDSM Implementation – Commercial Building

Implementing IDSM at your facility will mean selecting a combination of demand management strategies that are right for your business. The graphic below displays an example package of IDSM strategies for a large commercial office building.

Energy Efficiency (EE) Load Shifting (LS)  Utilize more efficient lighting  Add chilled water tank and utilize  Add variable frequency drives to air thermal energy storage (TES) to handlers shift load  Replace chillers with higher efficiency Peak Management (PM) Energy Conservation (EC)  Program the building energy management system (EMS) to  Install occupancy sensors avoid peaks in demand:  Enable sleep settings for office  Limit air handler speeds equipment  Adjust thermostat settings  Program thermostats to turn off during Demand Response (DR) vacancy  Program EMS for DR: Distributed Generation (DG)  Dim common area lighting  Add an array of photovoltaic (PV) rooftop panels  Limit air handler speeds  Adjust thermostat settings  Add fuel cells or engine-driven generators

18 Efficient Technologies for Commercial Refrigeration Example IDSM Loadshapes

The graphic above illustrates how implementing several DSM strategies can interact to affect a facility’s loadshape.  The baseline load shape represents a large commercial office building that operates from 6 am to 8 pm.  With Energy Efficiency (EE) and Conservation (EC) measures in place, we see a large reduction in overall energy use.  Adding Distributed Generation (DG), in the form of roof-mounted photovoltaics (PV), provides enough energy to flatten or possibly invert the load shape during daytime hours.  Adding Load Shifting (LS) using a thermal energy storage system creates a permanent shift in demand away from the peak hours of noon to 4 pm. The system charges again each night from midnight to 4 am.  And lastly, on a Demand Response (DR) event day, non-critical demand is reduced even further for a short period of time, typically two to four hours.

Efficient Technologies for Commercial Refrigeration 19 Example IDSM Strategies for Commercial Refrigeration

The following provides an example of demand-side management strategies that can be used with commercial refrigeration.

 Energy Efficiency (EE):  Use energy efficient display cases  Install night covers  Use efficient condensers and evaporators  Energy Conservation (EC):  Use anti-sweat heaters  Implement floating head pressure and floating suction pressure  Distributed Generation (DG) – Integrate photovoltaic (PV) rooftop panels and fuel cells  Load Shifting (LS) – Thermal energy storage (TES)  Peak Management (PM) – Use dimmers on lighting; use defrost controls  Demand Response (DR) – Use dimmers on lighting; use defrost controls; apply ventilation control

20 Efficient Technologies for Commercial Refrigeration The Efficiency and Demand Hierarchy

There are differences in conservation measures:  Energy efficiency measures (and energy conservation measures), produce a reduction of energy use (kWh) throughout the year.  A daily load shift involves taking actions to reduce or shift load specifically during the summer on-peak hours. This saves both on energy costs (kWh) and reduces demand (kW).  Demand response is an occasional, short-term reduction in load when requested by the utility companies during unusual events.

Energy Daily Demand Efficiency Load Shift Response

A reduction in kWh Actions taken to Reduce load (kW) throughout the year reduce or shift load when requested during summer during unusual 8,760 hours on-peak hours events (kWh and kW) Occasional, called Up to 900 hours by the utility during the summer

Efficient Technologies for Commercial Refrigeration 21 What is Title 24?

The California Code of Regulations (CCR) is the official compilation and publication of the state’s regulations. Properly adopted regulations that have been filed with the Secretary of State have the force of law. These are known as Title 24.

We will discuss Title 24 in more detail later; the following aspects of commercial refrigeration are affected by the code.

Condensers Fans Continuously variable speed

Controls Variable setpoint control logic to reset the condensing temperature setpoint

Specific efficiency Air-cooled: ≥ 65 Btuh/Watt Evaporative-cooled: ≥ 160 Btuh/Watt

Fin density ≤ 10 fins per inch Compressors Controls Floating suction pressure logic to reset the target saturated suction temperature (SST)

Liquid subcooling For low temperature compressor systems with design: . Cooling capacity ≥ 100,000 Btuh . Saturated suction temperature of ≤ -10°F Refrigerated display cases

Lighting Automatic controls required for walk-in coolers and freezers

Heat Recovery Heat for space heating ≥ 25% of sum of design Total Heat of Rejection for all refrigeration systems that have individual Total Heat of Rejection ≥ 150,000 Btuh at design conditions

22 Efficient Technologies for Commercial Refrigeration Reasons for Using Refrigeration

The main use of refrigeration is to preserve perishable commodities, particularly food, in edible condition. Almost half of retail food sales is made up of perishable or semi-perishable foods.

Food simply keeps longer when it is kept cold or frozen. Refrigeration is the only way to preserve food at “the peak of its quality” in its original fresh state—maintaining its appearance, odor, taste, and vitamin content.

To avoid product deterioration and spoilage, food products must be kept at safe temperatures during storage, processing, and while on display. The optimum temperature range for refrigerating fresh food is between 35 and 45 F.

Deterioration and Spoilage

The two major causes of product deterioration and spoilage can be classified as:  Internal agents  External agents

Internal agents refer to the natural enzymes found in all organic materials. These produce chemical changes in food after harvesting or killing that naturally cause deterioration and spoilage.

External agents describe the wide variety of microorganisms that grow inside and outside food and cause spoilage.

Both of these agents are involved in most cases of food spoilage and both must be destroyed or controlled in order to preserve food.

Efficient Technologies for Commercial Refrigeration 23 Microorganisms

The most common external agents of deterioration and spoilage are classified as microorganisms, which includes a large variety of microscopic minute plants and animals.

These tiny organisms are agents of fermentation, putrefaction, and decay. They are found in large numbers everywhere—in the air, the ground, water, and in the bodies of plants and animals.

The “top three” of particular interest within the context of preserving food are:  Bacteria  Yeasts  Molds

Let’s concentrate for a minute on bacteria. Bacteria are very simple forms of plant life made up of one single living cell. They reproduce by cell division. Bacteria growth rate varies based on many environmental conditions such as temperature, the amount of light, etc.

Given ideal conditions, bacteria can reproduce and grow to maturity in as little as 20 to 30 minutes. At this rate a single bacterium is capable of producing as many as 34,000,000,000,000 (34 trillion) descendants in a 24-hour period.

The good news is that the life cycle of bacteria is relatively short; from a few minutes to a couple of hours. This means that even under ideal conditions, they cannot multiply at anywhere near this rate.

The table below shows bacteria growth rate for milk, at various temperatures over different time periods.

The Growth of Bacteria in Milk in Various Periods

Temperature, F Time, in hours: 24 48 96 168 32 2,400 2,100 1,850 1,400 39 2,500 3,600 218,000 4,200,000 46 3,100 21,000 1,480,000 50 11,600 540,000 60 180,000 28,000,000 86 1,400,000,000

From ASRE Data Book, Applications Volume, 1956-57. Reproduced by the American Society of Heating, Refrigerating, and Air-Conditioning Engineers

24 Efficient Technologies for Commercial Refrigeration Required Storage Temperatures

The table on the previous page demonstrated that to keep bacteria growth controlled in milk, the colder the storage temperature the better.

Storage temperatures for frozen and non-frozen products will vary by type.  Cold storage (non-frozen product) temperatures vary from 34 through 50 F.  Frozen foods are stored at temperatures ranging from -35 up to 32 F. Frozen vegetables are stored at temperatures from 10 to 20 F. Lower than 10° causes vegetables to dehydrate and lose their flavor.  Pre-prepared meals, which are partially cooked, can be stored at zero to 15° for months without dehydrating.  Ice cream and citrus concentrates must be stored between -10 to -25° F for best results. Because ice cream is about 65% air, it will shrink nearly 60% if stored above zero degrees for 30 days or more. Premium ice creams have higher butterfat content and less air. They can be stored for longer periods at -5°.

There are a wide variety of display fixtures that can provide a range of storage temperatures.

Typical Storage Temperatures in Display Refrigerators Temperatures ° F Type of case Application Evaporator Discharge air Product Return air Open multi-deck Dairy 22 35 37 47 Deli 17 31 35 43 Meat 12 28 33 37 Produce 17 30 37 45 Frozen food -18 -5 0 0 Open single-deck Dairy/Deli (27” front sill height) 12 22 36 37 Dairy/Deli (31” & 33” front sill ht.) 17 26 35 35 Meat 17 26 35 35 Produce (bulk produce) 27 30 41 50 Produce (cut produce) 22 27 37 45 Frozen food -18 -8 1 2 Ice cream -28 -18 -8 -8 Tub Deli (narrow island) 17 28 36 37 Deli (wide island) 17 28 36 33 Meat (narrow island) 12 25 33 34 Meat (wide island) 12 26 34 31 Produce 22 34 40 48 Frozen food -23 -12 -1 0 Ice cream -33 -22 -11 -9 Glass door reach-in Frozen food -13 -2 0 2 Ice cream -23 -12 -10 -8

Efficient Technologies for Commercial Refrigeration 25

Walk-in cooler

Single-deck meat display refrigerator Multi-deck meat refrigerator Glass door, frozen food reach-in display case

26 Efficient Technologies for Commercial Refrigeration Refrigeration Units in California

There are approximately 700,000 refrigeration units in California. Over half are the reach-in type.

Type Approximate units in California Reach-in 405,000 Walk-in 125,000 Under counter storage 95,000 Display cases 35,000 Roll-in 25,000 On counter displays 18,000 (SCE, RTTC)

Benefits of Refrigeration

Refrigeration provides many benefits:  Reduces product shrinkage and spoilage losses  Provides automatic, constant, and consistent temperature control  Provides improved sanitation  Allows an attractive display of foods  Maintains the fresh appearance of food products  Is overall an economical operation  Refrigerated storage and distribution offers almost year-round availability of products

Efficient Technologies for Commercial Refrigeration 27 AHRI Standard 1200

The Air-Conditioning, Heating, and Refrigeration Institute (AHRI) is a trade organization that represents most of the North American manufacturers of central air-conditioning and commercial refrigeration equipment.

Among many other things, AHRI develops and publishes technical standards for industry products. According to AHRI, the “standards establish rating criteria and procedures for measuring and certifying product performance.”

AHRI Standard 1200, Performance Rating of Commercial Refrigerated Display Merchandisers and Storage Cabinets, was developed by the Commercial Refrigerator Manufacturers Division and is the latest standard for commercial refrigerated display cases.

This standard applies to the following standard Commercial Refrigerated Display Merchandisers and Storage Cabinets, provided that the cases are equipped and designed to work with electrically driven, direct expansion type systems:  Self-contained and remote commercial refrigerated display merchandisers and storage cabinets  Open and closed commercial refrigerated display merchandisers

This This standard does not apply to the following:  Refrigerated vending machines  Ice makers  Soft serve extruders  Secondary coolant applications

The purpose of this Standard is to establish definitions, test requirements, rating requirements, symbols, minimum data requirements for published ratings, marking and nameplate data, and conformance conditions.

This standard documents a method for determining energy consumption values for display cases (merchandisers) and freezers. The standard covers self-contained units with a factory-equipped condensing unit as well as cases with remote condensing units.

The standard’s methodology calculates the energy consumption of the electrical components that is required to maintain a specific temperature within the case. The components include those found within the case, including the lights, evaporator fan motors, etc., and the compressor unit.

Results are expressed in kWh per day per unit length of refrigerated space:  “Total Daily Energy Consumption (TDEC) for Self-contained Commercial Refrigerated Display Merchandisers and Storage Cabinets” and  “Calculated Daily Energy Consumption (CDEC) for Remote Commercial Refrigerated Display Merchandisers or Storage Cabinets.”

28 Efficient Technologies for Commercial Refrigeration

High-efficiency display case (Hussmann)

High Efficiency Refrigeration Display Cases

Newer, reach-in display cases have certain energy-efficient features:  Super T-8 or T-5 lamps with electronic ballasts  Brushless DC motors (BLDC) for evaporator fan motors, compressors, and condensers  Low or no anti-sweat glass, double pane doors

Efficient Technologies for Commercial Refrigeration 29 Night Covers for Display Cases

An important energy efficiency measure for refrigeration display cases is the use of night covers.

In an open refrigerated display case, the cold air spills out, and warm ambient air is drawn into the case. Film or blanket-type night covers for open vertical and horizontal display cases can help reduce infiltration and radiation heat losses—these covers help keep warm air out and refrigerated air in— which saves energy by reducing compressor run time. These covers reflect the heat that would normally enter open refrigerated display cases, and maintain even temperatures throughout the display case.

Refrigeration case covers help lower refrigeration equipment maintenance and grocery store heating costs. Compressors and store heating systems will operate more efficiently, less frequently, and will require less energy.

The best night covers for display cases have small perforated holes to decrease moisture buildup. Covers made of aluminum work better than those made of plastic.

One example is the aluminum thermal shields from Econofrost. Southern California Edison's Refrigeration and Thermal Test Center (RTTC) conducted tests with open refrigeration display cases, which concluded that aluminum thermal shields reduced energy use and lowered operating costs. The shields were closed for 6 hours and the results were approximately:  9% reduction in compressor power demand  6% reduction in total cooling load for the case  1 F reduction in average product temperature

ECONO-COVER® self-storing night covers for open refrigerated display cases and freezers (Econofrost)

30 Efficient Technologies for Commercial Refrigeration

More covers for display cases, horizontal and vertical (Eliason Corp.)

Glass Doors on Display Cases

Medium-temperature supermarket display cases are the most common type of fixture. Open multi- deck cases account for about 50% of the fixtures found in supermarkets. These cases are typically used to refrigerate and display meat, dairy, and deli products—the Food and Drug Administration (FDA) strictly regulates the temperature of these products.

This type of open case is vulnerable to infiltration of warm and moist air from the surrounding environment. This infiltration dramatically increases the cooling load and food product temperatures—infiltration accounts for more than 75% of the total cooling load of these display cases.

Efficient Technologies for Commercial Refrigeration 31 Retrofitting Display Cases with Glass Doors

Some open multi-deck medium-temperature display cases can be retrofitted with glass doors, which can help save on energy costs and can improve food quality.

Southern California Edison engineers conducted a study of the performance of an open five-deck fixture to see the benefits of retrofitting this type of case with glass doors with anti-sweat heaters. The significant findings of this study include:  Compressor power demand decreased by 87%  Cooling load decreased by 68%  Mass of collected condensate reduced by 88%  Product temperature decreased by 4.6 F  Refrigerant mass flow rate decreased by 71%

Base case Glass door retrofit

Test scenarios (SCE)

32 Efficient Technologies for Commercial Refrigeration Strip Curtains for Walk-in Boxes

Strip curtains or plastic swinging doors installed on doors of walk-in boxes or doorways of refrigerated warehouses can help reduce heating and cooling costs. These curtains consist of overlapping clear vinyl strips.

Benefits include:  Reduce moisture and frost build-up in coolers and freezers  Cuts compressor running time, increases efficiency  Eliminate temperature fluctuations  Prevent premature food spoilage

Examples of strip curtains

Efficient Technologies for Commercial Refrigeration 33 Auto-Closers for Main Cooler or Freezer Doors

An automatic closer is an easy way to save energy by making sure cooler and freezer doors stay closed. Research has shown that an average freezer tends to be left open or ajar, either intentionally or unintentionally, up to 1,000 hours per year. This wastes a lot of electricity. Auto-closers make sure that the door is fully closed every time it is opened. An auto-closer should be applied to the main insulated opaque door of a walk-in cooler or freezer. It must be able to firmly close the door when it is within one inch of full closure.

Below are some examples of auto-closers for cooler or freezer doors.

Self-closing, spring-assisted Spring-activated door closer Hydraulic door closer hinge for walk-in cooler (Kason) (Kason) (Kason)

Door Gaskets

Worn-out gaskets on the doors to walk-in or reach-in coolers or freezers can allow cooling energy to escape and increase your energy costs. Door gaskets are designed to keep air leakage to a minimum and they are easy to install and maintain. The seals around the perimeter of these doors should be checked regularly and replaced when they are deformed or torn.

Replacement gaskets should meet the manufacturer’s installation specifications regarding dimensions, materials, attachment method, style, compression, and magnetism (some gaskets are magnetic). Some freezer doors are designed with a channel in the door that is designed to accept replaceable snap-in and snap-out magnetic gaskets.

Gaskets

34 Efficient Technologies for Commercial Refrigeration Anti-Sweat Heater Controls

Anti-sweat, or anti-condensate heaters are typically installed in the glass doors of low-temperature refrigerated display cases to prevent a buildup of condensation on the glass and frame. They do this by heating the glass doors and case frame surfaces to a temperature above the dew point. These resistance heaters typically operate continuously, 24 hours a day, 7 days a week and use a lot of energy.

Anti-sweat heater controllers monitor the display case anti-sweat door heaters, and turn them off when they are not required.

Some types of these devices have sensors that measure the relative humidity in the air outside of the display case. At low humidity conditions, the controller reduces or turns off the anti-sweat heaters, which reduces energy use.

Other types of these controllers reduce or turn off the anti-sweat heaters based on the amount of condensation formed on the inner glass pane of the door. When the condensation has been removed by the heaters, the controller shuts them off.

Some of the controllers can be retrofitted to reach-in cooler or freezer glass display cases and can substantially reduce energy costs.

Anti-sweat heater controller (Door Miser)

Efficient Technologies for Commercial Refrigeration 35 Energy Efficient Solutions for Anti-Sweat Heaters on Refrigerated Display Cases  Pulse modulation control (PMC) mechanism controls the run time of the anti-sweat heater as a function of indoor relative humidity (RH). Power usage decreases proportionally as indoor RH is reduced.  Special polymer doors—glass heating is eliminated and electric resistance heaters are only used for the case frames. Special polymer doors eliminate the need to heat the glass doors, or door sash. The door frame continues to receive heat.

SCE tests using a typical frozen food reach-in display case in three scenarios: a) no anti-sweat heaters (base case), b) with PMC, and c) with special polymer doors:  In the test, RH was reduced from 55% to 35% total cooling load was reduced about 6% (solely due to changes in latent load).  However, with PMC, power usage decreased proportionally as RH was reduced, and total cooling load was reduced up to 17% (due to changes in latent load and anti-sweat heater heat dissipation into the case).  With special polymer doors, power usage was reduced by 7%. The cooling load reduction can be attributed to less latent load and partial reduction in anti-sweat heater heat, as well as possibly reduced heat conduction through the glass door.

The reduction in total cooling load reduced compressor power use:  With PMC, lowering the RH resulted in a decrease in compressor power of 18%  With the special polymer doors, a decrease in compressor power of 11%.

Both technologies prevented condensation from taking place at the exterior surface of the door glass.

Both technologies reduced:  Anti-sweat heater power use  Cooling load  Refrigerant mass flow rate  Compressor energy

The only apparent drawback was an increased fog recovery time of the glass door.

36 Efficient Technologies for Commercial Refrigeration Suction Line Insulation

Adding insulation to bare refrigeration suction lines, for lines that are accessible, is a very cost- effective upgrade. The suction line returns the cold refrigerant vapor to the compressor. Insulating this line prevents the vapor from heating up prematurely and maximizes the efficiency of the system by reducing the compressor’s energy use. Insulation that is exposed to outside weather should be covered with an aluminum jacket or protected in some other way.

Insulation that has deteriorated

Well insulated suction lines

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38 Efficient Technologies for Commercial Refrigeration Fundamentals of Refrigeration

This section includes the following topics:  A few refrigeration terms and concepts  Refrigeration basics and heat loads  Vapor compression system and the refrigeration cycle

A Few Terms and Concepts

Before we begin the explanation of refrigeration, let’s go over a few terms and concepts.  Heat is expressed in BTUs (British Thermal Units). A BTU is about the amount of heat emitted from a common kitchen match. Refrigeration moves heat (BTUs) from one place to another.  Capacity of a refrigeration system is expressed in tons of cooling. A ton of cooling is equal to 12,000 BTU/hr.

Ways that refrigeration system efficiency may be described include:  COP (Coefficient of Performance)—The cooling that the refrigeration system delivers divided by the input energy supplied to the compressor. Or simply BTU out/BTU in; or, equivalently, the heat absorbed from the refrigerated space divided by the energy supplied to the compressor (electricity converted to BTU). The higher the COP, the more efficient the refrigeration system. COP may be expressed at full or partial loads (e.g., COP at 50% load).   kW/ton (kilowatts per ton)—The kW needed to operate the compressor’s motor divided by the tons cooling the refrigeration system delivers. kW/ton is a common method of expressing system efficiency among engineers in the U.S. The lower the kW/ton, the more efficient the refrigeration system. kW/ton typically refer to the unit’s efficiency at the full rated cooling load. Efficiency at partial loads may be significantly different.  EER (Energy Efficiency Ratio)—The BTU/hours of cooling divided by Watts of electric input. EER and SEER (Seasonal Energy Efficiency Ratio), which measures the same ratio at different temperatures) are common methods of expressing efficiency for small air conditioning and refrigeration units. The higher the EER (or SEER), the more efficient the refrigeration system.

Efficient Technologies for Commercial Refrigeration 39 Refrigeration Basics

Refrigeration, in general terms, is a process that removes heat from one place to another in order to keep things cold. Refrigeration reduces and maintains the temperature of a space or material below the temperature of the surroundings.

To do this, heat is removed from the thing being refrigerated and is transferred to something else. For example, heat is moved from the inside of a refrigerator to the air outside.

Refrigeration works because it takes advantage of scientific laws that deal with:  Heat and the way it behaves  States of matter such as liquids and gases  The relationship between pressure and temperature

40 Efficient Technologies for Commercial Refrigeration The Heat Load

The heat load on refrigerating equipment is the heat that must be removed from the refrigerated space in order to produce and maintain the desired temperature .

There are several different kinds of heat loads that add up to the total heat load for a given piece of refrigerating equipment:  Heat from transmission: warm air that enters the refrigerated space through the walls, floor, and ceiling. Heat will always travel from a region of high temperature to a region of lower temperature. This means there is always a continuous flow of heat into the refrigerated region from warmer regions. To offset this flow of heat, insulation material is needed between the two regions.  Heat from air infiltration: heat that enters the space whenever the door is opened. Warm air from outside displaces the cooler air inside and must be replace.  Product load: the heat carried into the unit by the refrigerated product. For example, bringing in a case of warm, room-temperature sodas into a walk-in introduces product load into the cooler. Product load also includes the heat of respiration, which is the heat generated by fruits and vegetables as they ripen.  Other miscellaneous loads that also contribute to the load on refrigeration equipment: These include heat from workers entering the cooler, evaporator fan motors, heaters, lights, and other electrical equipment.

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42 Efficient Technologies for Commercial Refrigeration Vapor Compression System

The graphic below shows the basic components of a refrigeration system. The major components include the evaporator, compressor, condenser, and refrigerant flow control device (expansion valve). Heat is absorbed at the evaporator and is rejected at the condenser.

Basic refrigeration system components

Evaporator: provides a transfer surface for the heat being absorbed. The refrigerant absorbs heat from the refrigerated space in the evaporator.

Compressor: removes the refrigerant from the evaporator and raises the temperature and pressure of the vapor to a point where refrigerant vapor can be condensed.

Condenser: provides another heat transfer surface. Heat passes from the hot refrigerant vapor to the condensing medium (air or water).

Refrigerant flow control device: the expansion valve meters the proper amount of refrigerant into the evaporator.

Efficient Technologies for Commercial Refrigeration 43 Liquid Refrigerants

The basis of mechanical refrigeration is the ability of liquids to absorb enormous quantities of heat as they vaporize.

The refrigerant, sometimes called the working fluid, is merely a heat transfer agent. The refrigerant absorbs heat from the refrigerated space in the evaporator, carries it out of the space, and rejects it to the condensing medium in the condenser.

As it makes the cycle through the system, the refrigerant continuously changes state from a vapor to a liquid and back again.

As refrigerants, vaporizing liquids are easily controlled and the refrigerating effect can be started and stopped at will.

Also, the vapor can be easily collected and condensed back into the liquid state so that the same liquid can be used over and over again to provide a continuous supply of liquid for vaporization.

By controlling the pressure the vapor is under, the temperature at which the liquid vaporizes can be controlled.

The pressure can be controlled by regulating the rate at which the vapor escapes from the evaporator.

44 Efficient Technologies for Commercial Refrigeration As shown in the graphic below, different liquids evaporate at different temperatures. Common refrigerants evaporate at temperatures well below zero degrees Fahrenheit.

Evaporation Temp. Liquid (at normal pressure)

Water 212° F

Alcohol 152° F

Ammonia - 28° F

R-22 - 41° F R-404A - 52° F R-410A - 60° F

Maintaining a Constant Amount of Liquid in the Evaporator

Liquid refrigerant is continuously vaporized in the evaporator and must have a constant supply of liquid.  Refrigerant vaporizes in the evaporator because it absorbs heat from the refrigerated space.  To condense the vapor back into liquid only requires that the heat flows out of the vapor into another medium.

The material used to absorb the heat from the vapor is called the condensing medium. Water and air are the most common condensing media.

Efficient Technologies for Commercial Refrigeration 45 The Household Refrigerator

One way to understand the refrigeration process is to describe it using a typical household refrigerator. The diagram below shows the major inner components of a typical “over and under” household refrigerator.

This diagram shows the evaporator cooling coils located at the back of the freezer section and the condenser coils located underneath the refrigerator. The compressor also is located at the bottom of the refrigerator next to the condenser coils.

Other major components include the condenser fan, evaporator fan, thermostat, and the defrost (or condensate) drip pan.

Household refrigerator

46 Efficient Technologies for Commercial Refrigeration In simple terms, a refrigerator moves heat from the evaporator located in the freezer section and moves it through the condenser to the ambient air. The evaporator coils, the compressor, and the condenser coils are filled with refrigerant such as Freon, which is R-12 or, more commonly today, DuPont’s Suva, which is R-134a.  The refrigeration cycle in the refrigerator begins as the compressor pulls the refrigerant gas from the evaporator coils and compresses it, then pumps it into the condenser coils.  As the refrigerant gas moves through the condenser coils, it gives up its heat to the cooler ambient air outside the coils. The condenser fan helps the process by moving ambient air over the condenser coils.  When the refrigerant gas leaves the condenser coils, it has given up most of its heat. It then moves under pressure through the metering device to the evaporator coils. In a household refrigerator, the refrigerant metering device is a thin copper pipe called a capillary tube which used instead of an expansion valve.  When the refrigerant enters the evaporator coils, it expands and evaporates rapidly since the pressure in the evaporator coils is very low. When the refrigerant expands, it absorbs heat from the surrounding evaporator coils. (The surface temperature of the evaporator coils is typically below 0 degrees F.) The refrigerant gas is then pulled through evaporator coils by the compressor, which completes the refrigeration cycle. The evaporator coils absorb heat from the freezer section and the evaporator fan distributes the cold air to both the freezer and refrigerator sections.

Efficient Technologies for Commercial Refrigeration 47 Air Flow Inside the Refrigerator

A full-sized refrigerator has a large freezer compartment that maintains colder temperatures. Domestic refrigerators use small motor-driven fans to circulate cold air through ducts from the freezer section into the lower part of the unit.

48 Efficient Technologies for Commercial Refrigeration Refrigeration System Divided Into Two Parts

The refrigeration system is described in terms of two general parts: the “low side” and the “high side.” These describe the two sections according to the pressure exerted by the refrigerant.

The low-pressure side consists of the refrigerant flow control, the evaporator, and the suction line. (The suction line moves the low pressure vapor from the evaporator to the suction inlet of the compressor.)  This refers to the low pressure under which the refrigerant is vaporizing in the evaporator.  It is also known as “low side pressure,” the “evaporator pressure,” the “suction pressure” or the “back pressure.”

The high-pressure side consists of the compressor, the discharge or “hot gas” line, the condenser, the receiver tank (not shown), and the liquid line.  It is also known as the “high side.”  This refers to the high pressure under which the refrigerant is condensing in the condenser.

The “hot gas” or discharge line delivers the high-pressure, high-temperature vapor from the discharge of the compressor to the condenser. The liquid line carries the liquid refrigerant to the refrigerant flow control.

Part of the metering pressure control involves maintaining a “pressure differential” between the high and low pressure sides of the system in order to permit the refrigerant to vaporize under the desired low pressure in the evaporator while at the same time condensing at a high pressure in the condenser.

In the simple compression refrigeration cycle, the system maintains a low pressure at the evaporator, and a high pressure at the condenser.

Efficient Technologies for Commercial Refrigeration 49 Refrigeration Cycle

The most common method used for the refrigeration process is the vapor compression system, also called the simple compression cycle.  High-pressure liquid refrigerant is fed from the condenser on through the metering device. (The thermostatic expansion valve and capillary tube are typical metering devices.) The thermostatic expansion valve controls the flow of liquid refrigerant from the liquid line to the evaporator, and reduces the pressure of the liquid refrigerant entering the evaporator so that the liquid will vaporize in the evaporator at the correct temperature.  As the low-temperature refrigerant passes through the evaporator coil, heat flows through the walls of the evaporator tubing to the refrigerant, causing the evaporation to continue until the refrigerant is completely vaporized.  The refrigerant vapor leaving the evaporator travels through the suction line to the compressor inlet. Before the refrigerant vapor is compressed in the compressor, it is at the vaporizing temperature and pressure. (The vapor is under low pressure and at a low temperature.) The compressor takes the low-pressure vapor and compresses it, increasing both the pressure and temperature. (The temperature of the vapor is now above the temperature of the condensing medium.) The hot, high-pressure gas is forced out the compressor discharge valve and to the condenser, where the refrigerant vapor gives up heat to the lower temperature of the condensing medium. The condensing medium carries the heat away.  As the high pressure gas passes through the condenser, it is cooled by some external means. On air-cooled systems a fan and fin-type condenser surface is usually used. On water-cooled systems, a refrigerant-to-water heat exchanger is usually used. The vapor condenses into a liquid and flows back to the liquid line to repeat the cycle.

50 Efficient Technologies for Commercial Refrigeration Supermarket Refrigeration System Components and Flow

The graphic below shows the refrigeration cycle components as they are found in a supermarket configuration.

Efficient Technologies for Commercial Refrigeration 51 Relative Positions of System Components

The graphics below demonstrate how the same components in different systems can be placed in various configurations.

The graphic on the left below shows the compressor, condenser, and condenser fan all positioned above the evaporator and evaporator fan.

The graphic on the right shows a split system where the compressor, condenser, and condenser fan are located outside and the evaporator and evaporator fan are located inside the cooler.

Self-contained system Split system

52 Efficient Technologies for Commercial Refrigeration A Conventional Refrigeration System

All supermarkets have a mix of low-, medium- or high-temperature display cases to meet specific product refrigeration requirements. A very common refrigeration system configuration found in stores is the conventional (one-on-one) type.

Each conventional refrigeration system compressor has its own condenser/receiver, and each compressor serves a single line-up or several small display cases with similar temperature requirements.

The main components of the conventional refrigeration system are the compressor, condenser, expansion valve (TXV), and evaporator. The figure below illustrates a typical conventional refrigeration system found in many stores. This example shows a conventional system with an air- flow evaporator and an air-flow condenser.

Each compressor also has its own dedicated suction, discharge, and liquid lines. Conventional systems use older techniques and many are past their useful life. To provide refrigeration, the compressor in a conventional single-compressor system either operates at 100% capacity, or is off.

Conventional systems tend to be less energy efficient than newer parallel systems.

Conventional systems cannot take advantage of many of the possible methods for improving operational efficiency during periods of cooler ambient conditions (specifically, floating head pressure, which we’ll discuss later). One reason is that conventional systems must limit how much system capacity is allowed to increase during cooler ambient conditions because they must prevent the compressor from excessively cycling on and off.

As outdoor ambient temperatures drop, the compressor cycles off more frequently. Energy losses occur each time the compressor has to restart and re-establish design working temperatures in the refrigerant lines and evaporator. (A suction pressure switch on the compressor limits capacity by keeping the compressor head pressure artificially high, or else the condensing temperature is kept at a constant.)

Energy transfer Total heat of rejection (THR) Air-flow TXV evaporator

Air-flow condenser Energy transfer net refrigeration Compressor effort (NRE) Capacity steps: 100% Energy power 0% added heat of compression (HC)

Conventional refrigeration system (VaCom Technologies)

Efficient Technologies for Commercial Refrigeration 53 Parallel or Multiplex Refrigeration System

A parallel or multiplex system operates basically the same way as the conventional type of system except this type has several display case line-ups (or boxes) that are cooled by several compressors connected to common suction and discharge manifolds.  This method is applicable when a system has several evaporators running at similar temperatures that are required to meet varying refrigeration loads.  Typically, this method uses from three to nine compressors of unequal sizes. The multiple compressors work together to support several refrigerated display case lineups (evaporators). All the compressors and display case lineups in the system share common liquid supply and gas suction lines.  This more complex method is quite efficient and is consistent with the best current technology, and typically employs high-efficiency heat rejection, and ambient or mechanical subcooling.

The figures below and on the facing page illustrate basic high-efficiency multiplex systems. The example system below has three compressors, three evaporators (one evaporator is contained in a walk-in cooler), a liquid to suction subcooler, and an air-cooled condenser. It does not have subcooling. The system on the facing page has the same components, but does include subcooling.

Multiplex or parallel system (low- and medium-temperature systems without subcooling)

54 Efficient Technologies for Commercial Refrigeration

Multiplex or parallel system (low- and medium-temperature systems with subcooling)

Although many large supermarket chains continue to use conventional systems with one compressor dedicated to one case line-up, parallel refrigeration systems have become the standard for new construction for most supermarkets over the last fifteen years.

New racks can be used to retrofit conventional systems or early parallel systems. Retrofitting existing systems in older supermarkets may require complete renovation, including new compressor racks, refrigerant piping, replacing expansion valves, and perhaps replacing all of the cases.

A typical supermarket may have one or more medium-temperature parallel systems for meat, deli, dairy, and produce refrigerators, and the medium-temperature walk-in coolers.  The system may have a separate compressor for the meat or deli refrigerators, or all units may have a single compressor.  Low-temperature refrigerators and coolers are grouped on one or more parallel systems with ice cream refrigerators on a satellite or on a single compressor.

With parallel systems, compressors are cycled off and on individually in “steps” as system requirements change (variations in outdoor ambient temperatures or heat loads on the display cases).  A system with three compressors of the same size may have four capacity steps: 100%, 67%, 33%, and all off (0%).  This configuration provides substantial flexibility for varying system demand.

Condensers for parallel rack systems are typically located a short distance away from the compressor rack. The typical configuration uses one condenser to support the multiple compressors on one rack.

Parallel compressor racks to replace conventional systems can reduce energy use up to 50% when equipped with typical rack capabilities.

Efficient Technologies for Commercial Refrigeration 55 Advantages of parallel systems:  Require lower first cost in new construction  Provide ongoing savings in:  lower operating costs  longer compressor life  lower maintenance costs  built-in standby capacity  Accommodate future expansion needs

It’s Only A Matter Of Size

Smaller supermarkets and larger commercial facilities have many features in common. The way the refrigeration systems operate is the same—the refrigeration cycle is implemented using the same equipment components. The main difference is the scale or size of the operation.

For example, a typical commercial multiplex refrigeration system found in supermarkets may use seven compressors of around 40 horsepower for each compressor. This equals about 280 horsepower of compression which provides a total of about 200 tons of refrigeration.

Larger industrial applications will have basically the same configuration, except the individual compressors and total tons of refrigeration are much larger. One brewery, for example, has three 750 HP compressors and six 490 HP compressors for a total of over 6,000 HP. This equals about 5,200 tons of refrigeration.

56 Efficient Technologies for Commercial Refrigeration Sizing Multiple Compressors in Parallel Rack Systems

The compressors in a “standard” parallel rack system are sized so that all the compressors operating together meet the “design refrigeration load” (the amount of cooling that the system is designed to meet).

Parallel rack systems may be designed using multiple compressors of the same size, or using several compressors of different sizes. Efficient rack application must match loads to suction design temperatures and include from 6 to 9 capacity steps.

The graphic below demonstrates how a multiplexed system might use three compressors, rated at 5, 7, and 10 horsepower. These compressors can be programmed in stages that operate different combinations of compressors. Each programmed stage provides different percentages of total capacity to accommodate varying system load.

A microprocessor-based control system is often used with a parallel system. Each fixture must have independent temperature controls. The control system senses the refrigeration load (through suction pressure or display case temperature), and selects the combination of compressors that will most closely match the needed capacity with the load. A parallel system can also use compressors with adjustable-speed drives. This ability to vary the capacity helps maintain the highest possible system efficiency and can achieve dramatic energy use savings. Demand savings for the parallel system are about 20% of a refrigeration system’s demand.

Another configuration for providing variable capacity is a duplex system with variable speed drives. One compressor serves as the primary compressor, and the second serves as a backup. Both are configured with a variable frequency drive.

VFD VFD

Backup Primary compressor compressor Duplex system with variable speed

Efficient Technologies for Commercial Refrigeration 57 Check Your Understanding

1. There are several types of refrigeration efficiency measures that are fairly easy to implement in commercial facilities. Name a few.

2. Name two refrigeration system configurations for reach-in boxes.

3. The terms “parallel” or “multiplex” are used to describe refrigeration systems.

a) What are some features of this type of system?

b) What is another typical refrigeration system configuration?

58 Efficient Technologies for Commercial Refrigeration Refrigeration System Components

In this section we will take a closer look at the main refrigeration system components.

The topics for this section include:  Compressor design  Reciprocating compressors  Screw compressors  Scroll compressors  Condensers and heat rejection techniques  Air-cooled  Water-cooled  Evaporative condensers  Evaporators  Expansion valves

Efficient Technologies for Commercial Refrigeration 59 Compressor Design

There are several ways to classify compressor design. They can be classified in terms of:  The temperature they maintain (high, medium, or low system temperatures)  How they are constructed (enclosures)  How they compress refrigerant (compression technology)

Compressors Classified By the Temperature They Maintain

In the conventional system configuration, there are typically two types of compressors, categorized in terms of the temperature they maintain: medium-temperature and low-temperature compressors. (You will sometimes see a “very-low-temperature” classification. “High” temperature compressors are also used in HVAC systems.)

Medium-temperature compressors are used in systems that keep refrigerated product at above- freezing temperatures (see the table below).  Medium-temperature cases usually contain dairy products, beverages, meats, fruits, vegetables, and other non-frozen perishable products. Low-temperature compressors are used to preserve frozen foods.  The average temperature of a frozen food case is 0° F. The table below also indicates the typical refrigerant suction temperature range for these compressors (the temperature of the refrigerant leaving the evaporator).  Low-temperature compressors tend to have less load variation than medium-temperature units. (Most frozen food cases are enclosed so temperature fluctuations are minimized.)

Typical Refrigeration Temperatures Medium-Temp. Low-Temp. Compressors Compressors Product Temperature 30 to 42 F 0 to -20 F Refrigerant Suction Temperature 5 to 25 F -15 to -40 F

60 Efficient Technologies for Commercial Refrigeration Compressors Classified By How They Are Constructed

Another way to classify compressors is based on how they are constructed:  Hermetic Hermetic compressor designs use a sealed or welded enclosure around the compressor and the electric motor drive. In this type of design, the motor is cooled by refrigerant that circulates around the motor windings.  Semi-hermetic Semi-hermetic compressors, like the hermetic design, use refrigerant to cool the electric motor, but this type is accessible through bolted covers. Compose over 90% of compressors used in the refrigeration market. Two principal manufacturers are the Copeland Corporation and the Carlyle Compressor Company. Semi-hermetic compressors range in size from 15 tons up to 50 tons or more.  Open Open compressors are usually driven by an external electric motor. The refrigerant is held inside by a seal around the compressor shaft.

Compressors Classified by Their Method of Compressing Refrigerant

Yet another way to classify compressors is by their method of compressing the refrigerant. The refrigeration industry for the most part uses the following compression technologies:  Reciprocating compressors  Screw compressors  Scroll compressors

Efficient Technologies for Commercial Refrigeration 61 Reciprocating Compressors

Reciprocating compressors are used in the majority of supermarket refrigeration systems. They use positive displacement by means of pistons to compress the refrigerant.  Pistons move inside cylinders to reduce the volume of the vapor in the compression chamber.  A reciprocating compressor may have one or more pistons.  The pistons are usually driven directly through a pin and connecting rod from a crankshaft that is turned by an electric motor.

Reciprocating compressors may be classified as hermetic, semi-hermetic, or open. They are easy to operate at varying loads since they can efficiently operate with variable compression ratios.

Reciprocating compressor, internal view (Copeland)

Semi-hermetic reciprocating compressor (Copeland)

62 Efficient Technologies for Commercial Refrigeration Screw Compressors

Screw (or helical rotary) compressors, like reciprocating units, are positive displacement machines.  They have either two matched spiral-grooved rotors, (intermeshing “screws”) or one rotor with a “gate rotor.”  As they turn, the volume of the refrigerant chamber between the screws is reduced, compressing the refrigerant.  The screw compressor has nearly constant-flow performance and can provide high-pressure ratios.

Screw compressors:  Are reliable  Operate with reduced vibration, which means less refrigerant leakage  Are fairly new to supermarket installations

To achieve capacity control with small screw compressors, it is common to use variable speed drives.

Screw compressor rotors Twin screw compressor (ASHRAE)

Efficient Technologies for Commercial Refrigeration 63

Comparing parts: Reciprocating compressor left, and screw compressor right (Trane)

Small semi-hermetic screw compressor (Carlyle)

64 Efficient Technologies for Commercial Refrigeration Scroll Compressors

Scroll compressors are rotary motion positive-displacement machines.  They are found in small units used for domestic air conditioners and in the small commercial market.  They range in size from 1.5 to 35 tons.  This type is similar to screw compressors, but the refrigerant is compressed by using two meshed, spiral-shaped scroll rotors. Typically, one rotor is fixed and one is moveable.

Scroll compressor scrolls (Copeland)

Sealed hermetic scroll compressor, internal view (Copeland)

Scroll compressor (Copeland)

Efficient Technologies for Commercial Refrigeration 65 The refrigerant vapor is compressed by continually reducing the size of the refrigerant chamber.  The gas is compressed as the size of the pockets is progressively reduced as the scroll motion moves the pockets inwards towards the discharge port.  The moveable scroll rotates in “orbits” which is a sequence of suction (inlet), compression and discharge phases.

Scroll compressors are, in general, more efficient than other small compressors. They have efficiency ratings up to 83%, which is comparable to larger screw or centrifugal units.

Scroll machines have begun to enter the commercial refrigeration industry as an alternative to hermetic reciprocating compressors in self-contained equipment.

Scroll compressors:  Are setting the standard for efficiency in smaller systems (1 to 15 tons)  Are quiet and may be more reliable than reciprocating compressors  Are readily adapted for use with new, non-ozone depleting refrigerants  Work well with variable speed controls to save additional energy during non-peak load conditions  With only four moving parts (compared to over 30 moving parts for reciprocating compressors) are very reliable

Scroll compressor process (ASHRAE, Purvis, 1987)

66 Efficient Technologies for Commercial Refrigeration Digital™ Method of Capacity Control

Copeland Corporation incorporates capacity control by “axially separating” the scrolls. When the scroll parts are disengaged, there is no gas compression. By varying the amount of time the scrolls are separated, capacity can be varied from 0 to 100%.

Capacity is modulated by energizing and de-energizing the solenoid valve. When the solenoid valve is de-energized, the compressor capacity is 100%, and when the solenoid valve is energized, the compressor capacity is zero.

Whether the scrolls are engaged or separated can be controlled on demand and capacity is determined by averaging the time in each state. For example, to achieve 80% modulated capacity over a 10 second cycle, the compressor is engaged for 8 seconds and separated for 2 seconds. The compressor uses pulse-width modulation to switch between the loaded and unloaded states as the motor turns at constant speed.

The scrolls are separated by diverting a controlled amount of discharge gas to the suction side through a solenoid valve. By lowering the pressure in the modulating chamber, the scrolls separate and there is no compression.

Digital Scroll Compressor (Copeland)

Efficient Technologies for Commercial Refrigeration 67 The Copeland Digital scroll compressors “allow infinitely variable capacity modulation while reducing power consumption linearly.” The graph below shows how the power requirements vary as the load varies with this method for capacity control. The graph shows the power that is required as a percent of load.

Typical modulated power reduction (Copeland)

Variable Speed Compressor Control

Variable speed controls on compressors allow the output of the compressor to match the load requirements of refrigeration display cases.  An inverter is used to control the speed of the compressor and slows the compressor speed when load conditions do not require its full output.  Variable speed controls are easily applied to strategic compressors in a parallel system with uneven size compressors.  If a system is undersized and runs at full load most of the time, such as with low-temperature systems for freezer cases, variable speed controls do not offer potential savings.  For medium-temperature systems, savings of six to 10% may be achieved.

68 Efficient Technologies for Commercial Refrigeration Compressor Characteristics and Trends

The table below describes the typical refrigeration system compressors. Each of the types listed may be used in either medium- or low-temperature applications.

Compressor Characteristics and Trends Type Size Characteristics Market Trends Hermetic Reciprocating 1/3 to Low cost, small size The only self-contained model, used with 5 HP small and distributed refrigeration systems Semi-hermetic 1/3 to Reliable, wide Have now established about 95% of the Reciprocating 60 HP application range market share Scroll 1/3 to Low cost, small size, Small market penetration. 12 HP quiet operation Screw 15 to Large capacities, Increasing usage 80 HP* simple operation * Screw compressors exceed 1,000 HP in industrial versions

Compressor Efficiency The chart below demonstrates the relative efficiency (Btu/Wh) of compressors based on the application and temperature required. With respect to compressor efficiency, the colder the temperature requirement, the more energy is used. For example, to maintain a temperature of –25 F required by frozen food refrigerators, compressors operate in the range of 5 Btu/Wh. On the other hand, to meet the 40 F temperature requirement of supermarket preparation and cutting rooms, compressors can operate at a higher efficiency level, near the 13 Btu/Wh range. Based on the relative efficiency chart below, to maintain –40 F requires three times the energy as maintaining +40 F. So, to maximize compressor efficiency, system operators should attempt to maintain operating temperatures as high as possible for a given application.

Compressor efficiency at different temperatures

Efficient Technologies for Commercial Refrigeration 69 Compressor Summary

As a general rule, screw and reciprocating compressors have about the same efficiency. What’s more important is how they are applied in refrigeration systems.

The Copeland Discus type and high-efficiency reed type semi-hermetic compressors available today from Bitzer, Carlyle, and other manufacturers are from 8 to 15% more efficient than older compressors.

Compressors with the most recent design features are automatically used in new system construction. When a compressor burns out, it can either be replaced with an identical model, or it can be upgraded to a new model. An upgrade requires engineering and piping changes.

When owners are considering changing the system refrigerant from a CFC to an interim or long-term refrigerant, retrofitting operating compressors should also be considered.

A compressor does not have a specific rated capacity—it is only a pump. Its capacity is determined by different factors including changes in refrigerant density, changes in mass, etc. Specifically, a compressor’s capacity is determined by the favorable or unfavorable conditions dictated by the evaporator and condenser.

70 Efficient Technologies for Commercial Refrigeration Example Compressor Curves and Table

Efficient Technologies for Commercial Refrigeration 71

72 Efficient Technologies for Commercial Refrigeration Condensers and Heat Rejection Techniques

Condensers like evaporators are heat transfer surfaces. They contain a heat-exchange coil that extracts heat from the refrigerant and cools the refrigerant.

Heat from the hot refrigerant vapor passes through the walls of the condenser to the condensing medium (either air in air-cooled condensers or water in water-cooled condensers).

As the result of losing heat to the condensing medium, the refrigerant vapor is cooled and condensed into the liquid state.

The heat-transfer efficiency of a condenser is a function of:  The size of the coil  The temperature difference between refrigerant and condenser coolant  The thermal properties of the heat-exchange coils  The cleanliness of the coil (over time, condenser coils become dirty and must be cleaned periodically to maintain optimal efficiency).

Commercial refrigeration installations use three types of condensers:  Air-cooled  Water-cooled  Evaporative condensers

Efficient Technologies for Commercial Refrigeration 73 Air-Cooled Condensers

Air-cooled condensers use air as the condensing medium. They can be placed in a remote outdoor location or indoors with the compressor.

Since heat given off by the condensing refrigerant increases the temperature of the air, indoor air- cooled condensers can be used to heat portions of the building in winter.

Outdoor types range in size from 0.5 to 30 horsepower or more.

Air-cooled condensers have a greater installed cost and use more energy than evaporative condensers.  On the other hand, maintenance costs for air-cooled equipment are only about 25% of those for water-cooled equipment.  Also, they experience less capacity and efficiency loss from fouling than water-cooled equipment.  Air-cooled condensers are used in situations where water costs are high or when disposal is a problem or expensive.

Remote air-cooled condenser

74 Efficient Technologies for Commercial Refrigeration Water-Cooled Condensers

Water-cooled condensers (or cooling towers) use water as the condensing medium. Heat given off by the condensing refrigerant increases the temperature of the water used as the condensing medium.

Water-cooled condensers work best in hot, dry climates and are more energy efficient than air-cooled condensers. Water-cooled condensers are sometimes considered uneconomical for supermarkets because of the high costs of water and sewer fees.

Some supermarkets use water-cooled condensing units, since the trend is toward air cooling. Nearly all water-cooled condensing units are installed with a water-saving cooling tower because of the high cost of water and sewage disposal.

Air out

Eliminators Hot water in

Wet deck surface Air in

Refrigerant in Fan Water make-up Shell and tube condenser Pump Pan Cold water out Refrigerant out Cooling tower used with a shell-and-tube condenser (ASHRAE)

Efficient Technologies for Commercial Refrigeration 75 Evaporative Condensers

Evaporative condensers use both air and water as the condensing medium. This type rejects heat through the evaporation of water into an airstream that is blown or drawn across the condensing coil.  Refrigerant in the condenser is cooled initially from the evaporation of the water from the surface of the condenser.  The function of the air is to increase the rate of evaporation by carrying away the water vapor which results from the evaporating process.

Evaporative condensers:  Have the lowest installed cost and use less energy than air-cooled condensers. However, they have added annual maintenance costs that can make them uneconomical.  Are more efficient than air-cooled systems because they can operate at lower condensing temperatures.

Closed water condenser/evaporative cooler systems evaporative condenser cools water instead of refrigerant. Water flows in a closed, chemically stabilized circuit with a regular water-cooled condenser (a two-stage heat transfer system). Heat from the condensing refrigerant transfers to the closed water loop in the regular water-cooled condenser. The warmed water then passes to the evaporative cooler. High-efficiency evaporative condensers can reduce the temperature of high-pressure refrigerants about 10° F lower than a conventional air-cooled condenser because of the cooler air which is passed over the condenser coils. High-efficiency evaporative condensers should be used with floating head pressure to gain the most energy savings. This can reduce refrigeration energy use by 5%.

Discharge air

Water distribution system

Vapor in Coil Inlet air Liquid out louver screens Entering Entering air air

Pump

Evaporative condenser (Recold) Evaporative condenser, functional view

76 Efficient Technologies for Commercial Refrigeration Condenser Fans

Most condenser fans run for long periods of time. If standard-efficiency motors are replaced with high-efficiency motors, fan power requirements can be reduced by nearly one half.  When condenser fan motors fail, they should be replaced with high-efficiency units to achieve the shortest possible payback.  High-efficiency motors can be used with variable speed controls and with floating head pressure operation.

Example High-Efficiency Fan Motors

High-efficiency or “third generation” motors are specifically designed for air-moving applications. They offer a wide speed range and are programmable to provide a wide range of performance characteristics.

An example is the brushless, permanent-magnet DC (BLDC) motor, also called electronically commutated (EC) motor. The BLDC motor does not operate directly off a DC voltage source. This type of motor has a three-phase stator with windings (like an induction motor) and the rotor has surface-mounted permanent magnets. (The electromagnets do not move; the permanent magnets rotate and the armature remains stationary.) Commutation is performed electronically. To reverse polarity, the BLDC motor uses power transistors that are synchronized with the rotor position. BLDC motors often incorporate either internal or external position sensors to detect the actual rotor position. (The position can be detected without sensors.)

The motor uses a solid state, electronic controller for proper operation. BLDC motors are efficient and do not have carbon brush wear. Because the motor utilizes a permanent magnet rotor, there are near zero rotor losses. The product serves the indoor blower market for almost all residential HVAC systems and many commercial air distribution systems.

Brushless DC motor (GE Industrial Systems)

Efficient Technologies for Commercial Refrigeration 77 Condenser Efficiency

When considering a specific condenser design, there are a wide range of efficiencies (BTU/Watt) in the product catalogs. The catalog “nominal” size comes from HVAC practice. Air-cooled condensers:  The capacity varies with DBT (dry bulb temperature)  Past industry practice based on maximum system pressures  Typical, 10 to 20 degree TD

TD = temperature difference, which is the difference between the temperature of the refrigerant leaving the condenser to the incoming air temperature (the “leaving refrigerant approaches the entering ambient.”)

Evaporative condensers:  The capacity varies with WBT (wet bulb temperature)  Past industry practice based on first cost  Typically are getting sized larger for closer approaches as a result of efficient designs.

Air-Cooled Condenser Efficiency Examples

This graphic shows several air-cooled condensers from three different manufacturers (A, B, and C). There is a wide variation in system efficiency (in BTU of heating rejected per fan Watt) within a product line.

Variation in Efficiency

160

140 128.1 120

100 83.4 77.5 77 80 75.4 56.7 60 45.5 40.5 42.2 40 34.1

20 BTU/WATT WBT) 72 SCT, (90 BTU/WATT 0 A A A A A A B B C C Manufacturer

78 Efficient Technologies for Commercial Refrigeration High Efficiency Air-Cooled Condenser

Oversized air cooled condensers selected with optional low speed fans and at a lower TD can reduce compressor power with little or no increase in fan power.

Condenser size, floating head pressure and fan control strategies must be considered together. Early replacement of old style or deteriorated air cooled condensers can reduce energy and service costs.

Newer high efficiency air-cooled condensers use electronically commutated (EC) motors on the condenser fans.

Condenser fan with electronically commutated (EC) motor

Efficient Technologies for Commercial Refrigeration 79 Evaporative Cooled Condenser Efficiency Examples

Variation in Efficiency

310.6 300 250.5 250 213.3 200 161.8 151.7 150 130.2 115.3 117.7

100

50 BTU/WATT (90 SCT, 72 WBT) 72 (90SCT, BTU/WATT 0

A A-R A A B B C C Manufacturer

Evaporative Condensing

An evaporative condenser can be used in place of one or more air cooled condensers. Both condenser and compressor energy are substantially reduced and demand is sharply reduced.

Increased water costs can be up to half of energy savings. Operation at lower condensing temperatures can increase capacity and reliability of existing compressors and may fit well with CFC change-out plans.

High Efficiency Evaporative Condensing

Evaporative condenser efficiency can be improved by downsizing condenser ratings to reduce fan motor size and selecting the condenser at a lower TD. A variable speed drive can be applied to the condenser fan.

Application should be in conjunction with floating head pressure. Use of variable speed is important to obtain benefit of floating head pressure without excess fan power. Compressor life is extended by operating at low head pressures.

80 Efficient Technologies for Commercial Refrigeration Variable Speed Condenser Fan Control

Condenser fan power can be reduced by variable speed control of both single and multiple condenser motors. A TD-based control strategy is required.

Substantial savings are possible as well as accommodating floating head pressure without excessive condenser fan power. Control capability varies with manufacturer.

Combined Compressor and Condenser Performance

25 Compressor plus Condenser Power Minimum points 20

15

Compressor Power

10 Power(kW) Inefficient Condenser 5 Efficient Condenser

0 5 8 11 14 17 20 23 26 29 32 Condenser Size (application TD)

Efficient condensers use less power (kW) when compared with standard condensers.

Optimum system energy is the minimum total fan power plus compressor power.

A larger condenser has a smaller temperature difference (TD). For example, say the outside or ambient air is 100 F and the temperature of the leaving refrigerant is 120. Then there is a 20 degree TD (120 – 100).

More efficient condensers that have a larger coil require larger fans, which use more power. (Notice on the graph how the power use goes up.)

With a lower TD the compressor power use (kW) decreases because of a reduced condensing pressure.

Efficient Technologies for Commercial Refrigeration 81

Power consumption comparison: 10 fan, 14 fan, and 10 fan EC motor condenser configuration

82 Efficient Technologies for Commercial Refrigeration Exercise: Condenser Financial Analysis

On the following pages is a reproduction of a brochure from Bohn for different models of their Model BVF Belt Drive Air-Cooled Condensers used in refrigeration systems.

These models come in different sizes with many different variables that have an effect on system operations—total heat rejection, motor horsepower, the amount of heat they reject for a given load (kW), and more.

The goal is to find a condenser that is the right size that provides more heat transfer surface and uses less power over the long run, and therefore is more economical. Although it may cost more, a condenser with a larger coil rejects more heat and uses less energy. The question then is, is it more cost effective?

For models BVF 065 and BVF 069, the following information is found in the brochure.

Use the product catalog information (on the following pages), and fill the table below.

Model 065 Model 069

THR (total heat rejection) @ 30° TD

Motor HP (horsepower)

Number of fan motors

Full Load Amps (at 460V)

CFM (cubic feet per minute)

Weight

Length dimension (“A”)

Number of modules

Approximate price to end user $11,950 $14,430

Efficient Technologies for Commercial Refrigeration 83

84 Efficient Technologies for Commercial Refrigeration

Efficient Technologies for Commercial Refrigeration 85 86 Efficient Technologies for Commercial Refrigeration BELT DRIVE AIR COOLED CONDENSER SELECTION

CHARGE COST MODEL # MBH TONS R-22 HP KW KW/TON LF CFM CFM/TON LBS $ 11,950 O65 990 82.5 32 10 7.08 0.0859 100% 48,200 584.24 1450 $ 14,430 069 1055 87.9 48.1 4.5 3.30 0.0375 94% 44,000 500.47 1960

Given data found in the catalog and the cost of the units, we are able to calculate simple payback. Any payback around three years is generally considered economical.

BELT DRIVE AIR COOLED CONDENSER FINANCIAL ANALYSIS

ANNUAL ELECTRIC COST SAVINGS

MODEL # TOTAL HP TOTAL KW HOURS/YEAR kWh/YEAR COST/kWh COST/YEAR

065 10 7.08 3,000 21,255 $ 0.15 $ 3,188.21 069 4.5 3.30 3,000 9,896 $ 0.15 $ 1,484.45

ANNUAL ELECTRIC COST SAVINGS = $ 1,703.76

EQUIPMENT COST

MODEL # COST

065 $ 11,950 069 $ 14,430

ADDITIONAL CAPITAL INVESTMENT $ 2,480

SIMPLE PAYBACK PERIOD

ADDITIONAL YEARS TO MODEL # COST SAVGS/YR PAYBACK

069 $ 2,480 $ 1,703.76 1.46

Efficient Technologies for Commercial Refrigeration 87 Questions:

What is the minimum specific efficiency (Btuh/W) for Models # 065 and # 069?

Do these models comply with Title 24 code?

Condenser Specific Efficiency

§120.6(b)1E – Fan-powered condensers must meet the specific efficiencies in Table 120.6-C

Table 120.6-C: Fan-Powered Condensers – Specific Efficiency Requirements Condenser Type Minimum Specific Efficiency a Rating Condition

Evaporative-Cooled 160 Btuh/W 100°F Saturated Condensing Temp. (SCT) 70°F Entering Wetbulb Temp.

Air-Cooled 65 Btuh/W 105°F Saturated Condensing Temp. (SCT) 95°F Entering Drybulb Temp. a See §100.1 for definition of condenser specific efficiency.

Exceptions to the Specific Efficiency requirements:  Condensers with a Total Heat Rejection capacity of < 150,000 Btuh at the specific efficiency rating condition  Located in Climate Zone 1  Existing condensers that are reused for an addition or alteration

88 Efficient Technologies for Commercial Refrigeration Evaporators

Any heat transfer surface in which a refrigerant is vaporized for the purpose of removing heat from the refrigerated space is called an evaporator.

Evaporators come in a wide variety of types, shapes, sizes, and designs and are also called cooling coils. They may be classified in a number of different ways, such as type of construction, operating condition, method of air (or liquid) circulation, type of refrigerant control, and application.

Evaporator

Cool Tube evaporator (Cooltube, Inc.)

A common type of evaporator is the dry-expansion evaporator.  Liquid refrigerant is fed into this type by an expansion device.  The expansion device allows the liquid to enter the evaporator at a rate such that all the liquid is vaporized by the time it reaches the end of the evaporator coil.

Efficient Technologies for Commercial Refrigeration 89 Types of Evaporator Fan Motors

There are three types of electric motors typically used for walk-in cooler evaporator fans:  Shaded pole (75% of production is shipped with this type)  Permanent split capacitor (PSC), typically more efficient than the shaded pole motor  Brushless DC (BLDC) motors, typically the most efficient (also known as electronically commutated [EC] motors).

As a rule, the more energy-efficient motors dissipated less heat into refrigerated display cases and improve the case cooling capacity. Tests sponsored by Edison indicate a power savings of 24% from the PSC motors and 47% from the BLDC motors, when compared with the shaded pole motor.

Walk-in cooler showing evaporator

Single-deck meat display refrigerator showing evaporator and fan

90 Efficient Technologies for Commercial Refrigeration The three principal types of evaporator construction are:  Bare tube  Plate-surface  Finned

Bare tube and plate-surface evaporators are sometimes classified together as prime surface evaporators—the entire surface of both these types is more or less in contact with the vaporizing refrigerant inside.  In a finned evaporator, the tubes are the only prime surface. The fins themselves are not filled with refrigerant and are only secondary heat transfer surfaces. The function of the fins is to pick up heat from the surrounding air and conduct it to the tubes that carry the refrigerant.  Bare-tube and plate-surface evaporators are most frequently applied to applications where the space temperature is maintained below 34° F. At these temperatures, frost accumulation on the evaporator surface is unavoidable.  Frost accumulation on prime-surface evaporators does not affect the evaporator capacity to the extent that it does on finned coils.  Most evaporators, particularly the plate-surface type, are easy to clean and can be defrosted manually by brushing or scraping off the frost accumulation. Frost accumulation does not interrupt the refrigerating process.

Evaporator Temperature Settings

In some systems, storage temperatures (and corresponding evaporator temperatures) are set too low compared to what is needed to preserve product.

With improved air flow patterns, raising the temperature a couple of degrees is usually safe and will reduce energy usage. A rule of thumb is a 1 degree F increase in evaporator temperature will result in a 1% energy savings.

Efficient Technologies for Commercial Refrigeration 91 Evaporator Fan Controller for Walk-in Coolers

There is a controller on the market for medium-temperature walk-in coolers that can reduce energy consumption.

In most evaporator units, the air is cooled by propeller fans that are powered by small, fractional- horsepower motors. And as a rule, these fans operate continuously even when full air flow is not required.

One technique for saving on energy costs uses an inexpensive controller and a simple concept to slow down the evaporator fans when full-speed operation is not necessary. This speed-control technique runs the fans only as fast as the cooler needs at the time. It is easy to install, is often cost- effective, and often yields simple payback periods of one to two years.

The best fit for this type of controller are medium-sized, medium-temperature walk-in coolers with a dedicated refrigeration system that operates with single-phase powered evaporator fans. (The ideal application is in an oversized system.) This method only works with single-phase shaded pole and permanent split capacitor motors.

How It Works

An auto-transformer is installed in the evaporator motor electric power circuit. Temperature sensors (thermistors) are attached to the refrigerant line on both sides of the expansion valve. These detect refrigerant flow in the line. When cooling is not required and there is no refrigerant flow through the evaporator, the controller reduces the voltage to the evaporator fan motors. Power input is reduced by about 75 to 85% when operated at low speed. The fans maintain the required minimum air circulation.

Evaporator fan controller

92 Efficient Technologies for Commercial Refrigeration This control system has its pros and cons.  The technology is simple, direct, and relatively inexpensive to apply. It saves energy by reducing evaporator fan energy and from a reduced amount of heat introduced into the cooler from the evaporator fan motors. This decrease in heat reduces the cooler load and also the energy used by the compressor and condenser.  The magnitude of savings and cost effectiveness is site specific. Each situation has to be considered on its own merits. The manufacturer claims operating cost savings of up to 50%. Testing and review produced mixed results in terms of verifying savings.

Evaporator fan controller (Frigitek) and evaporator fan

Evaporator fan controller with data logger (Advanced Refrigeration Technologies)

Efficient Technologies for Commercial Refrigeration 93 Expansion Valves

Expansion valves are metering devices that regulate the flow of liquid refrigerant into the evaporator. Expansion valves also maintain a pressure differential between the high and low pressure sides of the system.

Expansion valves reduce the pressure of the refrigerant as it flows into the evaporator which causes the refrigerant to vaporize.

There are several types of metering devices. A typical type is the thermostatic expansion valve which keeps the evaporator completely filled with refrigerant under all system load conditions.

Conventional liquid-charged thermostatic expansion valve (Dossat)

94 Efficient Technologies for Commercial Refrigeration Electronic Expansion Valves

Electronic expansion valves also regulate the flow of refrigerant and are controlled electronically by either digital or analog circuits.

Applying electric expansion valves involves a valve, a controller, and control sensors. The control sensors are typically pressure transducers, thermistors, RTDs, or other pressure and temperature control sensors.

Typical piping schematics demonstrating applications of electric expansion valve (Sporlan Valve Company)

Efficient Technologies for Commercial Refrigeration 95 There are typically four types of actuation for electric valves:  Heat-motor operated  Magnetically modulated  Pulse width modulated (on-off type)  Step motor driven

Electric expansion valves are controlled using either digital or analog electronic circuits. Electronic control of valves is more flexible than traditional mechanical valves and makes possible “stopped” or “full flow” control schemes.

Electric expansion valves offer several benefits:  They permit control methods that are not refrigerant specific  They have a wide load range  They can be set remotely  They can respond to many different input parameters

96 Efficient Technologies for Commercial Refrigeration Refrigerants

In this section on refrigerants we will have a brief chemistry lesson, and learn about:  The common types of refrigerants used in refrigeration systems  Alternative refrigerants  Refrigerant issues

Refrigerants have the properties of providing a good heat-transfer medium in refrigeration systems. They are typically non-flammable, non-explosive, and non-toxic.

A Brief Chemistry Lesson...

In the periodic table of elements, only a small number of elements can be used to synthesize the compounds that can be used as refrigerants. Other compounds are solids, or are toxic, unstable, radioactive, or rare. Some compounds simply will not phase change—that is, they don’t react in a way required for a workable refrigerant. This leaves a relatively small number of elements for compounds that can be considered.

Periodic Table of Elements

Efficient Technologies for Commercial Refrigeration 97 Refrigerant Chemical Composition

The highlighted area in the table indicates the basic elements we can work with to make refrigerants: chlorine (Cl) and bromine (Br), hydrogen (H), carbon (C), nitrogen (N), oxygen (O), fluorine (F), and sulfur (S). Chlorine and bromine are elements in refrigerants that deplete atmospheric ozone.

The term CFC (chlorofluorocarbon) applies to a molecule that is fully “halogenated” (halogens are chlorine, fluorine, or bromine) and is a chlorinated fluorocarbon.

The term HCFC (hydrochlorofluorocarbons) applies to molecules containing hydrogen in addition to carbon, chlorine and fluorine. The hydrogen in HCFC tends to destabilize the molecule causing a shorter atmospheric lifetime and less impact on the ozone layer.

HFCs have only carbon, fluorine, and hydrogen with no impact on ozone depletion because there is no chlorine.

It is the very stable bonds in the CFCs that make for a long atmospheric life, and that allow time for CFCs to drift to the stratospheric ozone layer where they eventually break apart, releasing the chlorine atom and causing the destruction of ozone.

Most common refrigerants are composed of mainly one or two carbon atoms and many combinations with atoms of chlorine, fluorine, and in some cases, hydrogen. The figure below represents some properties of these elements and compounds made from them.

98 Efficient Technologies for Commercial Refrigeration

Properties of common refrigerant elements and compounds

Each of the points of the triangle represents a compound consisting only of the element at that point plus carbon. The top of the triangle, for example, represents a compound of chlorine and carbon.

The sides represent combinations of the elements at the adjacent points. The right side of the triangle, for example, represents various combinations of chlorine, fluorine, and carbon. The interior of the triangle represents combinations of all three of the elements plus carbon.  The top of the triangle, for example, represents a compound of chlorine and carbon.  The sides represent combinations of the elements at the adjacent points.  The right side of the triangle, for example, represents various combinations of chlorine, fluorine, and carbon.  The interior of the triangle represents combinations of all three of the elements plus carbon.

There are many different ways these elements can be combined, and how they are combined will determine whether a given refrigerant is a viable product.  As the graphic indicates, refrigerants that contain too much hydrogen are flammable and those that contain too much chlorine tend to be toxic.  So that leaves us with the area in the triangle that is not shaded for the best refrigerant choices. Also, refrigerants derived from the compounds along the bottom of the triangle do not contain chlorine and will have zero ODP (ozone depletion potential).

Efficient Technologies for Commercial Refrigeration 99 Safety Classifications

Although not indicated in their names, refrigerants also are classified into safety groups by using a combination of the letters A and B (for toxicity) and the numbers 1, 2, and 3 (for flammability). A2L and B2L are newer designations for “mildly flammable” refrigerants. Class A signifies refrigerants which are not toxic at concentrations less than or equal to 400 ppm based on a time-weighted average. Class B refrigerants are toxic at levels below 400 ppm. Class 1 indicates no flame propagation. Class 2L is mildly flammable and class 2 has a low flammability limit. Class 3 are highly flammable.

In the case of blends, there are two safety classifications — first, for the blend as it is formulated and second, for the worst-case “fractionation” (fractionation, simply put, is a change in composition primarily due to refrigerant leaking).

ASHRAE Standard 34 Safety Classifications of Refrigerants

Flammability in air at 60°C Low Chronic Toxicity High Chronic Toxicity and 101.3 kPa (TLV-TWA > 400 ppm) (TLV-TWA < 400 ppm)

No Flame A1 B1 Propagation

Mildly With a maximum burning A2L B2L Flammable velocity of ≤ cm/s

Low A2 B2 Flammability

High A3 B3 Flammability

ASHRAE Standard 34 safety classifications

Examples of Each Safety Classification

A1 Nearly all commercial refrigerants incl. R-12, R-502, R-22, R-134a, etc. A2L R-1234yf, R143a, R1234yf A2 R-152a, R-142b A3 R-290 (propane) B1 R-123 B2L R-717 (ammonia) [was B2] B2 R-30, R40 (seldom used) B3 Vinyl chloride

Examples of safety classifications

100 Efficient Technologies for Commercial Refrigeration Naming the Refrigerants

You may wonder how the names and numbers of refrigerants are determined, and what the numbers and the letters in the refrigerant names mean. Both the letters and numbers indicate the compounds that make up the refrigerant.

Refrigerant Numbering

The chemical composition of a refrigerant determines the refrigerant number. As refrigerants become viable commercial products, the American Society of Heating, Refrigeration, and Air-Conditioning Engineers (ASHRAE) assigns the numbers used to identify refrigerants. These numbers provide a shorthand method for determining the chemical composition of refrigerant compounds.

ASHRAE Standard 34 describes (in about a dozen pages) the details of the numbering system, which, with some knowledge of chemistry, can be understood in its entirety. The following few paragraphs review the basics of Standard 34, and explain some of the more common notations.

For pure refrigerants related to methane (only one carbon atom), to ethane (two carbon atoms), and, for most cases those related to propane (three carbon atoms), the molecular structure can be determined by the refrigerant number. The table below indicates to which numbering series each of these belong.

ASHRAE Standard 34 Refrigerant Numbers

000 series Methane-based compounds 100 series Ethane-based compounds 200 series Propane-based compounds 300 series Cyclic organic compounds 400 series Zeotropes 500 series Azeotropes 600 series Organic compounds 700 series Inorganic compounds 1000 series Unsaturated Organic compounds

ASHRAE Standard 34 refrigerant numbers

Efficient Technologies for Commercial Refrigeration 101 The zeotropic and azeotropic refrigerant blends are designated by a 400 or 500 number, respectively. These are assigned successive numbers as the refrigerants become commercially available. Inorganic compounds (those without carbon) such as ammonia, have a 700 number that is determined by adding the molecular weight of the compound to 700. (For example, ammonia, or R-

717 is an inorganic compound of the 700 series. The “17” is derived from NH3 where the atomic weight of Nitrogen is 14 and Hydrogen is 1. This gives us 14 + (1 x 3) = 17.) The sum of the atomic weights gives the molecular weight.

For hydrocarbons and halocarbons:  The number farthest to the right is the total of fluorine (F) atoms in the compound.  The second number from the right is one more than the number of hydrogen (H) atoms.  And the third number from the right is one less than the number of carbon (C) atoms, which is omitted if it equals zero.

Using these rules for R-22, we can determine the composition of this refrigerant’s molecules:  The number farthest to the right equals the number of fluorine atoms, which is 2;  The second number from the right minus one equals the number of hydrogen atoms (2-1=1);  And the first number is zero because it is one less than the number of carbon atoms (1-1=0).

R-22 Molecule

R-22 molecule

The number of chlorine (Cl) atoms in the compound can be determined by adding all the atoms that can be connected to the carbon atoms and subtracting the number of fluorine and hydrogen atoms. With R-22, there are four atoms connected to one bonded carbon atom. Since there are two fluorine atoms and one hydrogen atom, this would leave room for one chlorine atom.

102 Efficient Technologies for Commercial Refrigeration Now, with R-123, we can again determine the composition of this refrigerant’s molecules:  The number farthest to the right equals the number of fluorine atoms, which is 3;  The second number from the right minus one equals the number of hydrogen atoms (2-1=1);  And the first number plus one equals the number of carbon atoms (1+1=2).

R-123 Molecule

R-123 molecule

Once again, the number of chlorine (Cl) atoms in the compound can be determined by adding all the atoms that can be connected to the carbon atoms and subtracting the number of fluorine and hydrogen atoms.

With R-123, there are a total of six atoms connected to the two bonded carbon atoms. Since there are three fluorine atoms and one hydrogen atom, this would leave room for two chlorine atoms.

Efficient Technologies for Commercial Refrigeration 103 For 134a there is a lower case “a” after the number and 245ca has two lower case letters, “ca.” These lower case letters indicate the arrangement of the atoms attached to the carbon atoms. The term isomer is used to indicate that there are various ways to arrange the atoms (isomers have the same number and kinds of atoms, but in different arrangements).

For example, 134:

R-134 Molecule and 134a:

R-134a Molecule

R-134 and R-134a both have the same number of fluorine and hydrogen atoms, but in different arrangements. The more symmetrical molecule is indicated by the number only.

104 Efficient Technologies for Commercial Refrigeration The less symmetrical molecule is indicated by adding a lower case “a.” The symmetry is determined by subtracting the sum of the atomic weights of the atoms attached to one carbon atom from the sum of the atomic weights of the atoms attached to the other carbon atom. The smaller absolute value of the difference indicates the more symmetrical isomer.

Molecule symmetry

For the propane series, since there are three carbon atoms, there are even more possible combinations. In this case, the first lower case letter indicates the arrangement on the center carbon atom and the second letter indicates the symmetry of the atoms around the first and third carbon atoms. An example is 245ca.

Composition-Designating Prefixes

The letters used to designate refrigerant composition indicate whether chlorine, hydrogen, or fluorine are present. The capital letter “C”, for carbon, is preceded by the letters C for chlorine, F for fluorine, or H for hydrogen, as in CFC, chloro-fluoro-carbon or HFC, hydro-fluoro-carbon. These composition- designating prefixes are used primarily in non-technical publications where ozone depletion is of interest.

Otherwise, the more technically correct way to designate refrigerants is to put the upper case letter “R” in front of the refrigerant number to designate that the compound is a refrigerant, such as R-134a. Blends such as R-507, also can be written as R-125/143a (45/55) which gives the components of the blend (R-125 and R-143a) and their percentages (45% and 55%).

Efficient Technologies for Commercial Refrigeration 105 CFC Derivatives of Methane

The figure below shows the CFC derivatives of methane—these compounds have only one carbon atom. The CFCs that are being phased out (R-11 and R-12) are along the side of the triangle that have the characteristic of being fully halogenated; that is, they have a long atmospheric life.

CFC derivatives of methane

106 Efficient Technologies for Commercial Refrigeration CFC Derivatives of Ethane

The diagram below shows the CFC derivatives of ethane—these compounds have two carbon atoms.  The refrigerants R-123 and R-134a are in this family of compounds.  Both are in the area of the triangle where the best alternatives are found.

In the bottom row of the diagram are compounds that do not contain chlorine, and have zero ODP.

The common compounds used in refrigerants “blends” are indicated in the graphic. (Blends are refrigerants composed of more than one component and are discussed in detail later.)

CFC derivatives of ethane

Efficient Technologies for Commercial Refrigeration 107 Pure Refrigerants and Blends

Refrigerants can be classified as pure fluids or as mixtures or blends.  A pure fluid refrigerant is chemically made of one component of a single kind of molecule. At a given pressure, the temperature of a pure refrigerant does not change when it boils or condenses in the refrigeration cycle. Some examples of pure fluids used in refrigeration systems are R-12, R-22, and R-134a.  The terms mixture and blend are interchangeable and both describe refrigerants composed of more than one component or kind of molecule. The components used to make refrigerant blends are selected specifically to create a final product with specific characteristics. These characteristics, such as capacity, efficiency, discharge temperature, vapor pressure, etc., will vary depending on the percentages of the components that make up the blend.

Zeotropes and azeotropes are two types of blends.

As we discussed earlier, one way to distinguish zeotropes from azeotropes is by the ASHRAE number series given to these blends. Zeotropes are the 400 series and azeotropes are the 500 series.

Azeotropes

An azeotrope is a mixture of two or more liquids that boils at a constant temperature.

An azeotrope behaves basically like a single fluid. At a given pressure, the temperature remains constant as the refrigerant boils or condenses. This temperature can be either higher or lower than the boiling temperature of any one of the individual component liquids.

An azeotrope, at a specific pressure, does not change composition—that is, the components remain blended and don’t separate when the blend evaporates or condenses. This is because at a certain pressure the combination of components have one boiling temperature—its “azeotropic point.” (It may not behave this way at other pressures, but the differences are very slight.)

At one time, the most common azeotrope in wide use was R-502, a blend of R-22 (48.8%) and R-115 (51.2%) [typically written R-22/115 (49/51)]. For all practical purposes, R-502 performs like a single fluid even though the R-22 and R-115 are not chemically joined, only mixed together.

108 Efficient Technologies for Commercial Refrigeration Zeotropes

A zoetrope mixture is a blend with two or more components that, at a constant pressure, exhibits a distinct and substantial shift in temperature during condensing or boiling. The components in a zeotropes mixture do not have a constant boiling point (and therefore, there is no constant temperature of all of the components taken as a whole).

This temperature change during a constant pressure phase change is called glide, and varies with the components used in the blend. The amount of temperature glide (or boiling range) for a particular zeotropes is a measure of its deviation from being an azeotrope.

Some of the more common zeotropes that exhibit high glide include:  R-401A, a popular interim R-12 replacement which has an 11° F glide (boiling range).  R-407C, an R-22 replacement refrigerant, which has from 8 to 12° F glide.

Experience with zeotropes as replacements for R-12, R-22, and R-502 is growing, and all major refrigerant manufacturers now produce refrigerants with glide. Competent technicians find they are easy to use and require handling and servicing techniques similar to those commonly used with traditional refrigerants.

Glide

Glide is a temperature change during a constant pressure phase change.  Glide is a function of refrigerant blends—the vaporization temperature of “pure fluid” refrigerants does not change, and therefore this type does not have glide.  The amount of glide (or the vaporization or “boiling” temperature range) varies with the components used in a blend.

Refrigerant glide can be explained in terms of the nature or properties of the refrigerant (which is “temperature glide,” or glide due to a phase composition shift), and also in terms of glide caused by a drop in pressure in a heat exchanger and other “system” influences (“system performance” glide).

Temperature glide is caused by the effects of one refrigerant component evaporating or condensing before another component at a different temperature and pressure. This is glide due to a composition shift during a phase change.

Efficient Technologies for Commercial Refrigeration 109 Let’s look at temperature glide using the zeotropes R-407C as an example. R-407C is a blend of R- 32/125/134a (23/25/52) and has a 12° F glide or boiling range.

Each of the components of a refrigerant blend has a different relative volatility, which is to say they evaporate (change states) at different temperatures.

As the liquid exits the expansion valve and begins to vaporize, the vapor in the evaporator consists of a portion of all three blend components. The vapor is, however, richer in the most-volatile component (R-32 in this example) because it is vaporized at a faster rate than the other components with higher evaporation points.

This means that the composition of the remaining liquid shifts as the liquid vaporizes. What remains is a liquid richer in the less-volatile components (R-125, and R-134a in this example). The composition of the liquid continues to shift as the liquid turns to vapor, until the liquid reaches its maximum vaporization point.

The diagram below demonstrates that as the vaporization point rises, the composition and temperature of the refrigerant gas changes. This temperature glide is caused by the changing proportions of the individual components that are vapor and liquid.

Eventually the last drop of liquid refrigerant evaporates and the refrigerant continues to the compressor and on through the rest of the refrigeration cycle.

Example of temperature glide

110 Efficient Technologies for Commercial Refrigeration Refrigerant Choices for Commercial Refrigeration

There are many possible options for selecting a particular refrigerant and refrigeration equipment configuration.

For conversions, there may be a wide range of equipment, of varying ages and conditions. For new equipment choices, the application and other factors will dictate the choice.

For systems and when considering new systems there are many variables to understand and consider when evaluating and selecting a replacement refrigerant:  The environmental impact including ozone depletion potential (ODP), global warming potential (GWP), and total equivalent warming impact (TEWI) ratings. (TEWI can be used to calculate the influence on the global warming effect of individual refrigeration plants.)  Safety and health issues regarding toxicity and exposure limits, and flammability  Chemical behavior  Application range (the temperatures at which the refrigerants work best)  Refrigeration capacity and relative efficiency  How long the refrigerant will be available  Cost

Ideally, an alternative refrigerant would have zero or low ODP, low direct GWP, and a level of energy efficiency that either meets or exceeds the refrigerant it is replacing.

When selecting a refrigerant, it is important to consider how well suited the refrigerant is to its application, including operating temperatures, where and how it will be used, and operator expense.

Calculating the TEWI factor (Bitzer International)

Efficient Technologies for Commercial Refrigeration 111 Interim Refrigerant Alternatives

The so-called interim refrigerant alternatives are options for the short-term since these refrigerants will, at some time in the future, be phased out.  However, in certain retrofit situations, especially for refrigeration systems with some life left, and in situations where a store is remodeled often, it may make good economic sense to convert existing systems and use interim refrigerants.  A general rule of thumb is to use interim refrigerants for conversions and long-term refrigerants for new equipment.

Using some interim refrigerants in a typical retrofit situation means lower first costs, but at the expense of higher energy costs. The energy efficiency of some of the interim blends is questionable.

The principle interim refrigerants for refrigeration systems include R-22, a pure HCFC that contains chlorine, and refrigerant blends that all contain some R-22.

The interim choices predominantly available for refrigeration are:  R-401A (MP-39), a near drop-in replacement for R-12.  R-402A (HP-80), a near drop-in replacement for R-502.  R-22, a possible replacement for both R-12 and R-502.  R-408A, a drop-in replacement for R-502.  R-416A (FR-12), a near drop-in replacement for R-12.

R-401A

R-401A (MP-39), whose composition is R-22/152a/124 (53/13/34), is a near drop-in replacement for R-12. This refrigerant has a high glide temperature range (8 F) making performance reliant on the heat exchanger configurations in existing systems. In the testing at the SCE refrigeration lab at 90 F saturated condensing temperature, R-401A was less efficient than R-12 by 2% (see “Commercial Refrigerant Research Project [A Case In Point]” later in this chapter).

R-401A is relatively easy to install in existing R-12 conventional systems. A single oil change to an AB oil and other minor system adjustments are required. The estimated conversion cost for a conventional store ranges from $12,000 to $15,000.

112 Efficient Technologies for Commercial Refrigeration R-402A

R-402A (HP-80) is a near drop-in replacement for R-502. Its composition is R-125/290/22 (60/2/38). R-402A is noted to be 4% less efficient than R-502 in DuPont literature. In the testing at the SCE refrigeration lab, at 90 F condensing, R-402A was 11% less efficient than R-502.

R-402A is relatively easy to install in existing R-502 conventional systems. A single oil change to an AB oil and other minor system adjustments are required. The estimated conversion cost for a conventional store is $12,000 to $15,000.

One issue regarding R-402A is its high operating pressure. It is not recommended for air-cooled systems in hot climates.

R-22

R-22 is an interim HCFC refrigerant that is typically known for its proven performance, and good efficiency. It has known characteristics, compressor performance, and oil compatibility. R-22 does experience high discharge temperatures which can affect equipment reliability. (The high discharge temperatures was one of the primary reasons for the development of R-502.)

R-22 has the advantage of being much less expensive than the blend alternatives. The initial low costs of R-22 and subsequent costs to replenish leaks can be attractive for certain systems. Potentially, the cost could increase on a supply-and-demand basis as production limits are imposed.

R-22 is not recommended for use in converting conventional systems.  Converting R-12 systems to R-22 requires changes to the compressor, expansion valve, and piping. R-22 operates at higher pressures and has 50% more refrigerating effect than R-12. Existing compressors cannot typically be changed to R-22 from R-12. The lower mass flow with R-22 typically requires that suction line riser sizes must be reduced.  R-502 systems converted to R-22 require suction desuperheating equipment; however, R-22 could be considered for certain R-502 parallel systems.

Efficient Technologies for Commercial Refrigeration 113 R-22 was essentially the only option available to the commercial refrigeration industry when the CFC phaseout began. Most users converted new low-temperature systems from R-502 to R-22. Many medium-temperature systems were already using R-22 or if not, were changed over.

Even as R-134a became available as a medium-temperature option, many applications such as supermarkets stayed with R-22 due to the larger physical compressor and piping sizes associated with R-134a. Also, R-22 has good efficiency characteristics on medium-temperature applications. For some medium-temperature applications, some of the new HFCs used to replace R-502 are not as efficient as R-22.

R-22 Summary

Environmental ODP .055; HGWP .35 Interim or Long-term Interim alternative; phaseout starts in Alternative 2004, total phaseout in 2030 Safety A1 Capacity compatible with air conditioning Refrigeration Capacity and medium-temperature refrigeration; and Relative Efficiency high efficiency Availability Widely available Cost $1.50 to $2.00 per pound Operating Pressure High-pressure Chemical Behavior Pure chemical, no glide Air conditioning and medium-temperature Application refrigeration

114 Efficient Technologies for Commercial Refrigeration The Future of R-22 in Industrial Refrigeration

R-22 is essentially at the end of its use in new systems. However, manufacturers continue to make R-22 systems, and their price is increasing. In 2010, R-22 is scheduled for phase out in all new equipment; after 2010, chemical manufacturers may still produce R-22 to service existing equipment. After 2020, there will no longer be any new R-22 produced; however, the use of existing R-22, including refrigerant that has been recovered and recycled, will be allowed to service existing systems.

Some companies continue to use R-22 in new construction with the following justifications:  R-22 continues to be relatively inexpensive. However, repair service using R-22 can and will get much more expensive as its production continues to decrease and after production ceases in 2020.  R-22 system challenges are known, and HFCs still have a somewhat limited experience.  Installation costs are reasonable (pipes are relatively small).  Total R-22 phase-out is still years away.  HFCs should be considered for these reasons:  R-22 cost will eventually increase due to supply and demand pressures.  In smaller systems, there are high discharge temperatures with single-stage R-22 systems (or use of liquid injection which affects reliability).  A zero-chlorine choice is more environmentally friendly.

HCFC phase-out chart

Efficient Technologies for Commercial Refrigeration 115 R-422D

R-422D is classified as a “near drop-in replacement” for R-22. This is an HFC blend that is not scheduled for phaseout under current regulations.

Two manufacturers of R-422D are:  DuPont™ ISCEON® MO29  Honeywell Genetron 422D

Components include R-125, R-134a, and R-600a (Isobutane).

Blend component Weight % R-125 65.1 R-134a 31.5 R-600a 3.4

Features of R-422D include:  Safety classification is A1 (non-flammable, low degree of toxicity)  Has a 100 year Global Warming Potential (GWP) of 2729  A non-ozone depleting HFC refrigerant

Retrofitting an R-22 system with R-422D involves the following process:  Evacuate the R-22  Change the valve systems  Charge with R-422D in a liquid form  Check your pressures.

A polyolester (POE) lubricant “will enhance oil return.” Be sure to check with compressor manufacturer for the proper oil. (Most R-22 AC systems use mineral oil lubricants.) Also, because the mass flow of R-422D is higher than that of R-22, you should evaluate the expansion device.

116 Efficient Technologies for Commercial Refrigeration R-438A

One manufacturer of R-438A is DuPont™ with their product ISCEON® MO99™ .

R-438A is a zeotropic refrigerant blend that is suitable for positive displacement compressors and with direct expansion evaporators.

Blend component Weight % R-32 8.5 R-125 45.0 R-134a 44.2 R-600 1.7 R-601a 0.6

With DuPont’s product, in most systems, the existing mineral oil (MO) or alkylbenzene (AB) lubricants can be used. This means you don’t need to change to a polyolester (POE) lubricant. (However, R- 438A is compatible with POE.)

Features of R-438A include:  Safety classification is A1 (non-flammable, low degree of toxicity)  Has a 100 year Global Warming Potential (GWP) of 2264  A non-ozone depleting HFC

R-408A

R-408A, a blend of R-125/143a/22 (7/46/47), is an R-502 alternative being marketed recently by Elf Atochem.

R-408A has characteristics that justify further investigation, including lower operating pressures than R-402A and higher efficiency than R-402A and R-502. R-408A has a 1 F temperature glide. Although an oil change is not required for conversions, a change to MO/AB is recommended.

In a demonstration project conducted by Southern California Edison, lab results from tests run in October 1995 for R-408A are good. The results were interesting in that R-408A out-performed R-502 by 7 or 8% and demonstrated a 6% capacity increase.

Efficient Technologies for Commercial Refrigeration 117 Long-Term Refrigerant Alternatives

One alternative for commercial refrigeration systems is to use long-term refrigerant alternatives that do not contain chlorine (such as pure HFCs or blends that contain HFCs). These alternatives may be used in either conventional or parallel applications in new equipment (and in some cases, converted equipment).

Refrigeration systems that implement long-term refrigerants have more expensive up-front costs, but will result in increased energy cost savings.

The long-term zero-chlorine refrigerant options include:  R-134a (pure HFC)  R-404A  R-507  R-407A  Hydrofluoroolefins (HFOs); see below  And more

118 Efficient Technologies for Commercial Refrigeration R-134a

R-12 has one zero-chlorine replacement refrigerant: HFC-134a. This was the first HFC in large-scale production due to its selection by all major automotive manufacturers. Its cost has come down rapidly as production facilities have come on-line. R-134a is not a good alternative for new systems for practical reasons (compressor displacement and line sizes), but it could be considered for replacement of R-12 in existing medium-temperature systems instead of R-401A.

R-134a has similar pressures, thermodynamic properties and other characteristics as R-12. For medium-temperature commercial refrigeration applications, R-134a can be used as a retrofit replacement for R-12 with few problems. The primary requisite for a retrofit is the conversion from mineral oil to a polyolester (POE) oil, which requires multiple oil changes to reduce the residual mineral oil concentration to 5% or less.

The disadvantage of multiple oil changes could possibly be outweighed by the lower cost of the refrigerant over time and, arguably, the fact it is a “permanent” solution. However, when compared to R-12, an efficiency decline of 3% is noted by DuPont and the SCE lab tests show a decrease of 8% at 90 F condensing temperature.

R-134a was initially installed in a number of supermarkets as the first HFC installations in built-up commercial systems. These were medium-temperature applications, with R-22 being used for low temperature. When HFC blends became available to replace R-502 (and R-22) in low-temperature applications, it was immediately used for medium- temperature loads as well. The primary advantage of the higher-pressure HFC blends over R-134a is a reduction in system cost due to smaller compressors and line sizes.

The use of R-134a in new commercial refrigeration systems appears to be concentrated in small, medium-temperature systems and self-contained equipment.

Some elastomers used with R-12 are not compatible with R-134a. Also, compressors manufactured before 1975 have different motor winding insulation materials than later models, which may not be compatible with R-134a.

Efficient Technologies for Commercial Refrigeration 119 Some previous problems with R-134a conversions may be the result of high moisture levels or simply that poorly maintained systems were converted. The mixture of POE oil and HFCs tends to release existing system deposits which can contaminate compressors, valves, and other components.

R-134a Summary

Environmental ODP: 0; HGWP .28 Interim or Long-term Long-term alternative Alternative Safety A1 Refrigeration Capacity Similar capacity and efficiency as R-12 and Relative Efficiency Availability Widely available Because of a two-step manufacturing Cost process, it has higher costs that HCFCs. $3.75 to $4.50/ per pound Similar operating pressures as R-12 Operating Pressure Chemical Behavior Pure refrigerant with no glide Air conditioning and refrigeration; widely Application used in automobile air conditioners

R-404A

R-404A is an HFC blend composed of R-125/143a/134a (44/52/4) that replaces R-502 in both low- and medium-temperature applications. R-404A is one of the primary choices available for new commercial refrigeration systems and is approved and rated by major compressor manufacturers.

Initially introduced by DuPont, R-404A is now produced by DuPont, AlliedSignal, and Elf Atochem. R- 404A has a small temperature glide and a relatively high global warming index that gives some concern regarding very long-term viability.

Efficiency of R-404A is generally lower than R-502, particularly at higher condensing temperatures. DuPont shows a 10% lower efficiency (under standard conditions not representative of a supermarket). SCE lab testing showed an 8% lower efficiency at 90 F condensing. EPRI testing shows a 6% efficiency decline when compared with R-502, for an operating system that included mechanical subcooling.

120 Efficient Technologies for Commercial Refrigeration Conversions to R-404A require a change to polyolester (POE) oil, including multiple oil changes to reduce the residual mineral oil concentration to 5% or less.

R-404A Summary

Environmental ODP 0; HGWP .94 Interim or Long-term Long-term alternative; R-125/143a/134a Alternative (44/52/4) Safety A1 About the same as R-502 at lower Refrigeration Capacity condensing temperatures, decreasing capacity at higher condensing temperatures Available from DuPont, AlliedSignal, Elf Availability Atochem Cost $6.70 to $8.50 per pound Operating Pressure High-pressure Chemical Behavior Minimal (1 F) glide Application Refrigeration

R-507

R-507 is a two-component HFC blend offered by AlliedSignal that replaces R-502 in low- and medium-temperature applications. Its composition is R-125/143a (45/55). R-507 is another of the primary choices available for new commercial refrigeration systems and also approved and rated by major compressor manufacturers.

SCE testing showed a 5% better efficiency with R-507 than R-404A, which other testing tends to support. However, many consider the two refrigerants to be approximately equal. R-507 has no consequential temperature glide. R-507 requires a change to POE oil, including multiple oil changes to reduce the residual mineral oil concentration to 5% or less.

R-507 Summary

Environmental ODP 0; HGWP .98 Interim or Long-term Alternative Long-term alternative; R-125/143a (45/55) Safety A1 Refrigeration Capacity Low-temperature, R-502 replacement Availability Available from AlliedSignal Cost $7.25 to $7.50 per pound Operating Pressure High-pressure Chemical Behavior No glide Application Refrigeration

Efficient Technologies for Commercial Refrigeration 121 R-407A

R-407A is R-32/125/134a (20/40/40). R-407A (KLEA-60) is of interest in two respects: First, it has lower global warming potential than either R-404A or R-507, which may be of importance in the future. Second, it is a high glide (10 F) refrigerant, which may offer improved efficiency if properly applied and controlled.

In certain water-cooled systems, the counterflow heat exchange properties of R-407 might have a definite advantage.

R-407A Summary

Environmental ODP 0; HGWP .49 Interim or Long-term Long-term HFC alternative; R-32/125/134a Alternative (20/40/40) Safety A1; non-flammable Availability Widely available; ICI produces KLEA 60 Cost Approximately $6.75 per pound Operating Pressure High-pressure Chemical Behavior 13 F glide Application Refrigeration

R-22 Compared with R-404A and R-507

As stated earlier, the HCFC R-22 in some situations might be considered as an “interim long-term” alternative in addition to R-404A or R-507. R-404A or R-507 are considered “long-term” alternatives. But which is the best choice?

R-22 could be a choice for new systems, especially for high-leakage systems. A change to R-22 can lower costs, especially for markets with a short remodel cycle (markets typically remodel every seven to 10 years). Also, HFCs may have problems not yet apparent.

After consideration of R-22 and R-134a, the primary choices available for new commercial refrigeration systems are R-404A and R-507. Both were designed as low-temperature R-502 replacements but are being applied in low- as well as medium-temperature systems. In fact, nearly every supermarket chain that is using R-404A or R-507 for low-temperature systems is using the same refrigerant for the medium-temperature systems.

122 Efficient Technologies for Commercial Refrigeration At the beginning of the CFC phaseout, many companies rapidly moved to R-22 as an alternative to R-12 and R-502. R-22 has been used for many years, and while it has certain undesirable characteristics, the risks and challenges are well known. Many chains continue to use R-22 with the following justifications:  R-22 continues to be relatively inexpensive.  R-22 system challenges are known, and HFCs still have a limited track record.  Installation costs are reasonable (pipes are relatively small).  There are currently R-22 “drop in” replacements.

While R-22 continues to be a good refrigerant that will probably be available for the next decade, transition to HFCs should now be considered for these reasons:  R-22 cost is increasing rapidly due to supply and demand pressures.  There are high discharge temperatures with single-stage R-22 systems (or use of liquid injection which affects reliability).  R-22 systems with a two-stage configuration are more complex and have increased service costs.  A zero-chlorine and low greenhouse gas choice is desirable from an environmental perspective.

New Refrigerant: Hydrofluoroolefins (HFOs)

Hydrofluoroolefins are relatively new refrigerants (HFO = hydrofluoroolefin) that have a low Global Warming Potential.

Of interest, R-1234yf (HFO-1234yf), is a refrigerant developed by DuPont and Honeywell that meets the European Union directive to phase out refrigerants with greater than 150 GWP in air-conditioning applications for new cars, starting January 1, 2011.

With a GWP of 4, this refrigerant has both an atmospheric lifetime and impact on global warming that is over 300 times less than R-134a. HFO-1234yf has an atmospheric lifetime of only 11 days -- compared to 13 years for R-134a and more than 500 years for CO2. As a mobile air conditioning refrigerant, Honeywell claims that HFO-1234yf is a near drop-in replacement for R-134a and will allow fast and easy adoption for automakers.

Another refrigerant option to R-134a is the DuPont product Opteon™ XP10 refrigerant (XP = extra performance). This is an azeotropic refrigerant blend based on HFO-1234yf with a GWP close to 600, the lowest GWP nonflammable refrigerant based on HFO-1234yf.

Efficient Technologies for Commercial Refrigeration 123 Retrofit Options for Existing Systems

On the following pages are tables that provide some information on retrofit options for existing R-12 and R-502 systems.

These tables summarize the issues and considerations for changes from R-12 and R-502 to other refrigerants, comparing system characteristics, and giving some indication of how appropriately certain refrigerants might serve as replacement alternatives.

The emphasis is on the interim refrigerant alternatives. However, a retrofit might make use of long- term refrigerant if it makes sense for the given situation.

Existing R-12 Medium-Temperature Systems

Retrofit Options for Existing R-12 Medium-Temperature Systems

R-12 Option Type Issues and Considerations Replacement HCFC R-22  Higher pressures, re-design required (Interim)  No oil change required  New compressor required  New expansion valves and (probably) distributors  Usually requires reduction in suction riser size HCFC R-401A  Similar pressures, no compressor change Blends (MP-39)  9 F temperature glide (Interim)  Single oil change to AB oil  Requires change in dryer type  No thermostatic expansion valve (TXV) change  15 - 20% capacity increase  2 - 3% efficiency decrease R-401B  Similar to 401A with higher pressures (MP-66)  Suitable for some ice makers and lower temperature R-12 applications R-409A  No oil change required (FX56)  + 2% capacity increase

124 Efficient Technologies for Commercial Refrigeration

Retrofit Options for Existing R-12 Medium-Temperature Systems (continued)

R-12 Option Type Issues and Considerations Replacement HFC R-134a  Similar pressures, no compressor change (Zero  No temperature glide Chlorine  Multiple oil changes to POE oil Long-Term Alternative)  Requires change in dryer type  No TXV change required  Check seal compatibility on valves, etc.  Systems with Carlyle compressors require an oil pump change  Caution on pre-1975 compressors (check materials compatibility)  Typically no capacity problems; capacity remains the same  5 - 13% efficiency decrease Complete R-404A  Requires new compressor system, expansion System R-507 valves, and distributors Change R-407A  Multiple oil changes to POE oil  Reduce suction line risers  May need to upgrade piping on air-cooled systems

Existing R-502 Systems

Existing parallel systems are primarily R-502 systems. Generally, these experience the most frequent large refrigerant loss events, and for this reason, deserve special attention. The refrigerant choices for R-502 parallel systems include R-402A, R-404A, R-507, and R-407A.

On air-cooled systems, operating pressures definitely become a concern. R-402A in particular will exceed the rated pressures for the larger discharge lines on these systems. While the risk of tubing failure is probably low, the legal exposure should be avoided if choices are available that do not exceed the design ratings.

On parallel systems, floating head pressure more closely follows ambient conditions, requires a little more control, but saves energy. This option should definitely be implemented at the time of a retrofit. At lower head pressures, R-404A and R-507 appear to offer good efficiencies, essentially the same as R-502, and possibly better with medium-temperature applications.

Efficient Technologies for Commercial Refrigeration 125 An interesting alternative for existing R-502 medium-temperature systems is R-22. Pressures are lower, existing compressors will work, and the refrigerant cost is low. For systems with inherently high refrigerant loss rates, R-22 could be the best choice due to lower ongoing costs. There is some risk in this choice since R-22 has production caps that could trigger a supply and demand pinch long before its phaseout begins. (Phaseout began in 2004 with a production limit of 99.5% below U.S. baseline by 2020 [EPA]).

Retrofit Options for Existing R-502 Systems

R-502 Option Type Issues and Considerations Replacement HCFC R-22  Higher pressures, re-design required (Interim)  No oil change required  Compressor capacity usually adequate  Requires new expansion valves and (possibly) distributors  May require reduction in suction riser size HCFC R-402A  Somewhat higher pressures, no compressor Blends (HP-80) change required (Interim)  Single oil change to alkyl-benzene oil  Requires change in dryer type  No TXV change required  Copeland compressors need special relief valve  Possible piping pressure rating problems on large air-cooled systems  10 - 12% capacity increase  6 - 16% efficiency decline R-402B  Similar to R-402A, but higher pressures (HP-81)  Suitable for some ice makers HCFC R-408A  Similar pressures, no compressor change Blends  1 F temperature glide (Interim)  No oil change required, but MO/AB recommended  No TXV change required  6% capacity increase  7 - 8% efficiency increase

126 Efficient Technologies for Commercial Refrigeration

Retrofit Options for Existing R-502 Systems (continued)

R-502 Option Type Issues and Considerations Replacement HFC R-404A  Similar pressures, no compressor change (Zero R-507  No or minimal temperature glide Chlorine)  Multiple oil changes to POE oil  Requires change in dryer type  No TXV change required  Check seal compatibility on valves, etc.  Systems with Carlyle compressors require an oil pump change  Caution on pre-1975 compressors (check materials compatibility)  R-404A: minimal capacity difference; 2 - 12% efficiency decline  R-507: slight capacity increase; +1% to -5% efficiency difference R-407A  Similar to R-404A and R-507 except R-407A R-407B and R-407B have a significant temperature glide (6 - 10 F) and may require additional expansion valve adjustments  R-407A: 8 - 9% capacity decrease; 6 - 8% efficiency decrease  R-407B: 1 - 2% capacity decrease; slight efficiency decrease Complete R-404A  Requires new compressor system, system re- System R-507 design Change R-407A  Requires multiple oil changes to POE oil  May need to change expansion valves and reduce suction line risers if adding subcooling  May need to upgrade piping on air-cooled systems

Efficient Technologies for Commercial Refrigeration 127 Options for New Refrigeration Equipment

Installing new refrigeration equipment opens the doors to many options and provides a “clean slate” with which to start. A conventional system and long-term refrigerant might be considered, or a new parallel system and a long-term refrigerant.

This section discusses some of the refrigerant and system options for new systems for new medium- temperature and new low-temperature systems.

New Medium-Temperature Systems

The process for selecting new equipment for medium-temperature systems is very similar to previous R-12 systems except that changes in compressor capacity, horsepower, and line sizing must be taken into consideration.

Although R-22 will be phased out in the near future, it is listed here as an option for new systems since it may be a reasonable choice in some situations.

Options for New Medium-Temperature Systems

R-12 Option Type Issues and Considerations Replacement HCFC R-22  Proven performance, good efficiency (Interim)  Size lines large enough for future HFC refrigerant  Consult compressor manufacturer regarding oil selection for future HFC transition HFC R-134a  Requires POE oil (Zero  Requires large displacement compressors Chlorine) and large line sizes similar to R-12  Efficiency decline R-404A  Require POE oil R-507  May need to use heavy wall piping on air- R-407A cooled systems to meet Mechanical Code requirements R-407C  Similar to above with 6 - 10 F glide  Potential efficiency gains with heat exchanger optimization

Future R-410A  Operates at very high pressures Options (AZ-20) R-717  Requires indirect systems, uses additional (NH3) energy  Many code issues not resolved

128 Efficient Technologies for Commercial Refrigeration New Low-Temperature Systems

New low-temperature systems provide additional options for consideration. There are various selection criteria, including system efficiency, simplicity, initial cost, maintenance cost, and others.

Some options include:  Single-stage systems with liquid injection. These can be used for either single units or parallel racks and existing compressor designs can be modified for liquid injection.  Two-stage systems for industrial refrigeration system applications. These options can achieve maximum efficiency by incorporating intercooling and flash gas removal. There are higher initial costs, but two-stage systems are cost-effective on a life-cycle basis. Also, there will be higher maintenance costs due to additional components and control complexity.  Internally compounded compressors used with either single or parallel racks.

Options for New Low-Temperature Systems

R-12 Option Type Issues and Considerations Replacement

HCFC R-22  Liquid injection or compound compressors or (Interim) two-stage system recommended due to high discharge temperature  Size lines large enough for future HFC refrigerant  Consult compressor manufacturer regarding oil selection for future HFC transition HFC R-404A  Use POE oil (Zero R-507  May need to upgrade piping on air cooled Chlorine) R-407A systems to meet Mechanical Code requirements Future R-410A Options (AZ-20)  Operates at very high pressures R-717  Requires indirect systems, using additional (NH3) energy  Difficulty with low temperature indirect fluids  Many code issues not resolved

Efficient Technologies for Commercial Refrigeration 129 Natural Refrigerants

Carbon dioxide (CO2)

 CO2 has high value as indirect phase-change fluid  Low temp demonstrated  Medium temp emerging  Possible use in direct (compressor) systems

Ammonia (NH3)

 There is the potential to increase NH3 applications by using indirect design and low-charge systems  High efficiency  Lacking small compressors, etc.  Concerns for toxicity and codes

130 Efficient Technologies for Commercial Refrigeration Indirect Refrigeration Systems

One interesting long-term alternative system is an indirect refrigerant approach for use in supermarkets.

Instead of refrigerant piped directly to the fixture coils, refrigerant is used to chill a brine, glycol, or other indirect fluid which is pumped to the display cases through a secondary loop. Refrigerant charge for the entire store can be reduced to 300 pounds or less. Also, this type of system brings improved efficiency when compared to new halocarbon refrigerants and is halogen-free.

The primary challenge was to identify an appropriate indirect fluid that can be pumped economically. This technology requires new display cases and concerns include energy use required for longer pipes, pumping needs, etc. Indirect system retrofits are today a viable alternative.

Chillers that use ammonia (R-717) is one option considered for indirect systems. Ammonia chillers have made some progress in the air-conditioning chiller market. Ammonia is most easily used in water-cooled or evaporative-cooled configurations, but is also offered in an air-cooled design by one or more manufacturers.

Ammonia has a number of very attractive characteristics, including:  Zero ozone depletion  Zero direct global warming (greenhouse) effect  Low cost  High theoretical efficiency  Low required mass flow per ton of refrigeration

Ammonia in commercial refrigeration applications is limited by code restrictions because it is flammable and toxic. Proponents of ammonia are addressing these issues with research into indirect systems, low refrigerant charge, and special ventilation systems. Dealing with accidental release includes various methods to absorb the ammonia quickly before people are harmed. Possibilities could include diffusion systems (the ammonia is diverted to a water tank) or deluge systems (water is sprayed onto the ammonia and exposed area).

Traditionally, ammonia has been used in large plants. The lack of small, cost-effective compressors and other components suitable for small commercial systems limits somewhat the application of ammonia. Ammonia also has high discharge temperatures. Air-cooled systems therefore typically utilize screw compressors that mitigate the high temperatures by using built-in oil cooling.

Copper cannot be used with ammonia, so all heat exchangers and system piping must use steel or aluminum tubing. Also, semi-hermetic compressors are not feasible, which means ammonia systems will need to use an open-drive compressor.

Efficient Technologies for Commercial Refrigeration 131 Carbon Dioxide in Indirect Cascade Refrigeration Systems

Carbon dioxide (CO2, R-744) has been used as a refrigerant from the beginning of the 20th century. After falling out of favor to other more “modern” refrigerants, carbon dioxide may be experiencing a resurgence thanks to technological advances such as extremely thin and strong aluminum tubing.

There’s much talk these days about global warming, which is the rise in temperatures caused by an increase in the levels of greenhouse gases due to human activity, and the greenhouse effect, which is caused by certain gases (and clouds) absorbing and re-emitting the infrared radiating from Earth's surface.

There are benefits of using CO2 as a refrigerant to replace other refrigerants that contribute to global warming and ozone depletion. By using CO2 as a refrigerant, you minimize a lot of potential greenhouse gas emission compared with an HFC refrigerant that may leak out of a refrigeration system.

Carbon dioxide is a natural refrigerant that has no ozone depletion potential, and insignificant global warming potential. Also, CO2 is very inexpensive—at least 75% cheaper than other refrigerants.

Because CO2 is a non-toxic, non-flammable refrigerant, it is considered a food-quality grade refrigerant—if it should come in contact with food, the products are not damaged and are still consumable.

132 Efficient Technologies for Commercial Refrigeration Some commercial refrigeration systems use an HFC/CO2 sub-critical cascade system with or without a secondary fluid.

Combining two compression cycles allows each of the circuits to operate at lower compression rates, which optimizes energy efficiency. The HFC load is limited to the high pressure side of the cascade. (There are many refrigerant options for the “high side.”) This second circuit is used to condense the CO2.

HFC/CO2 sub-critical cascade system

CO2 systems operate at very high pressures and they require compressors that can withstand high operating pressures. A CO2 compressor must have an advanced shell construction, internal leakage control, and a special lubrication system. CO2 compressors may have better efficiency and lower refrigerant costs. Compared to other refrigerants, the required flow rate for CO2 is lower and the compressor is much smaller than with an HFC.

CO2 compressor (Danfoss)

Efficient Technologies for Commercial Refrigeration 133 This page intentionally blank

134 Efficient Technologies for Commercial Refrigeration Refrigerant Management Program Rules

The Refrigerant Management Program requires specific best management practices for businesses (non-residential) with refrigeration systems to reduce emissions of refrigerant.

"The regulation affects any owner or operator of a facility with a stationary, non-residential refrigeration system using more than 50 pounds of a high-global warming potential (GWP) refrigerant. The threshold of more than 50 pounds of high-GWP refrigerant is based on the single refrigeration system with the largest refrigerant charge. It is not the cumulative refrigerant charge from all refrigeration systems, at a facility." (California Environmental Protection Agency, Air Resources Board)

The Refrigerant Management Program specifies rules for leak detection, monitoring, and repair; retrofit or retirement plans; recordkeeping; facility registration; annual reporting; and fees. Also, service practices apply to any person who services an appliance using a high-GWP refrigerant. Reporting and recordkeeping requirements also apply to distributors, wholesalers, and reclaimers of high-GWP refrigerants.

Regulation requirements will be phased in over time depending on facility size.

Refrigeration systems are categorized based on amount of high-GWP refrigerant:  Large: systems using 2,000 pounds or more, approximately 2,000 facilities:  Cold storage warehouses  Manufacturing  Some supermarkets  Medium: systems using 200 pounds or more, but less than 2,000 pounds, approximately 8,000 facilities:  Smaller warehouses  Many supermarkets  Small: systems using more than 50 pounds, but less than 200 pounds, approximately 10,000 facilities:  Some pharmacies  Some grocery stores

Facility category Refrigerant capacity of largest system

Large 2,000 pounds and above Medium 200 to under 2,000 pounds Small Over 50 to under 200 pounds

Efficient Technologies for Commercial Refrigeration 135 Leak Repair and Recordkeeping

As of January 1, 2011, there are leak detection and monitoring requirements as well as recordkeeping requirements. These apply to all facilities, regardless of size.

Leak Repair  Fix all leaks within 14 days of detection  Refer to special repair provisions if leaks cannot be fixed within 14 days  Check system for leaks after repair  Use only U.S. EPA-certified technicians

Retrofit and Retirement Plans

If leak repair fails, a facility must follow the Retrofit and Retirement plan for that system. If a leak cannot be fixed, the facility must retire the equipment within six months after the initial detection of a leak.

Recordkeeping

Recordkeeping is required for facilities with a refrigerant charge of greater than 50 pounds of high- GWP refrigerant. Keep all service records on site for at least 5 years for each refrigeration unit, including those concerning:  Leak inspections  Installation, calibration and annual audits of leak detection systems  Refrigerant purchases  Shipment of refrigerants for reclamation or destruction  Calculations, data, and assumptions used to determine the refrigerant capacity.  Retrofit or retirement plans

Distributor, Wholesaler, and Reclaimer Prohibitions

Effective in 2012, reporting and recordkeeping requirements apply to distributors, wholesalers, and reclaimers of high-GWP refrigerants.

136 Efficient Technologies for Commercial Refrigeration Large Facilities  Registration—was due March 1, 2012  Annual reporting—starting in 2012, report of the previous year is due by March 1  Fees—$370 per facility paid upon initial registration and annual renewal  Inspection schedule requirement began on January 1, 2011:  Monthly for systems fully enclosed within a building or structure  Every three months for non-enclosed systems  None for systems with automatic leak detection that meets specifications  Monitoring—Requires installation of an automatic leak detection system if the refrigerant circuit, compressor, evaporator, condenser or other component with a high potential for leakage is fully enclosed within a building or structure

Medium Facilities  Inspection schedule requirement began on January 1, 2011:  Every 3 months  None for systems with automatic leak detection that meets specifications  Registration—was due March 1, 2014  Annual reporting—as of 2014, report of the previous year is due by March 1  Fees—$170 per facility paid upon initial registration and annual renewal

Small Facilities  Inspection schedule requirement began on January 1, 2011:  Annually  None for systems with automatic leak detection that meets specifications  Registration—will be due March 1, 2016  Annual reporting—none  Fees—none

Efficient Technologies for Commercial Refrigeration 137 Energy Implications

New construction:  Direct refrigerant systems are most efficient option  Indirect design:  HFC primary system cooling a secondary circulation fluid  Reduces HFC charge to the compressor room & condenser  Extra heat exchange, pumping costs, and heat gains  Less optimal overall system designs (less obvious)  Potential large increase in energy with glycol systems  Glycol only on applicable to medium temperature  CO2 proven on low temperature, energy equal to DX HFC

Retrofits:  Opportunity: combine energy efficiency upgrades with leak detection and mitigation budgets  Caution on system conversions: if energy use increases, no incentives and adds to greenhouse gases

Operations:  Running low on charge increases energy use  Important message to owners: manage tendency to defer leak repairs and recharge

138 Efficient Technologies for Commercial Refrigeration Regulated Refrigerants

Refrigerants regulated under the Refrigerant Management Program include any refrigerant that is an ozone depleting substance, or any compound with a global warming potential (GWP) value ≥150.

The table below lists some common refrigerants. Some are high-GWP refrigerants regulated under the Refrigerant Management Program; others are alternative substitute refrigerants that are not regulated under the program. CO2 and NH3 are non-high-GWP refrigerant alternatives and are not subject to the rule. (Note: this is not a complete list of regulated refrigerants.)

Common Refrigerants Regulated Under the Refrigerant Management Program and Non High-GWP Refrigerant Alternatives Ozone Global Refrigerant Refrigerant Common Refrigerant Applications Depleting Warming Designation Name Potential Potential R-11 CFC-11 Chillers 1 3,800

R-12 CFC-12 Chillers and Refrigeration Systems 1 8,100

R-502 CFC-502 Low Temperature Refrigeration Systems 0.25 4,700

HCFC-22 HCFC-22 Chillers, Refrigeration Systems, and AC Systems 0.05 1,500

HCFC-123 HCFC-123 Chillers 0.02 90

R-134a HFC-134a Chillers, Refrigeration Systems, and AC Systems 0 1,300

R-404a HFC-404a Low Temperature Systems 0 3,900

R-407c HFC-407c Chillers, Refrigeration Systems, and AC Systems 0 1,800

R-410a HFC-410a Air-conditioning Systems 0 2,100

R-507a HFC-507a Low Temperature Refrigeration Systems 0 4,000

R-744 CO2 (Carbon Dioxide) Refrigeration Systems 0 1

R-717 NH3 (Ammonia) Commercial and Industrial Refrigeration Systems 0 0

Source: California EPA, Air Resources Board

Efficient Technologies for Commercial Refrigeration 139 Commercial Refrigerant Research Project (A Case In Point)

In 1993, the Technology Planning and Development Department of Southern California Edison Company (SCE), Rosemead, CA, initiated a research project with the catchy title “Development and Demonstration of Energy-Efficient Commercial Refrigeration System Options using Non-CFC Refrigerants.” (The project was conducted in the SCE Refrigeration and Thermal Test Center [RTTC] founded in 1996.)

The purpose of the research project was to develop environmentally compatible energy-conserving and demand-shifting commercial refrigeration systems using new non-chlorinated refrigerants, and to provide SCE’s customers—principally supermarket and restaurant chains, and food-processing and cold storage facilities—with valuable research results addressing viable technical and implementation alternatives for regulation compliance and cost forecasting. Project management was provided by SCE personnel, and the project consulting team included ASW Engineering Management Consultants, Tustin, California, and VaCom Technologies San Dimas, California.

The refrigerants that were tested included two CFCs, four HCFCs, and six HFCs. The following information is extracted from the December 1994 report on the project, and provides information on the lab configuration, testing procedures, results of lab and field tests, industry impact information, and more.

140 Efficient Technologies for Commercial Refrigeration The first phase of the research project involved initial screening tests of refrigerants using supermarket display cases and associated refrigeration equipment. The test lab was constructed at Southern California Edison’s Highgrove Research and Development Test Center near Riverside, California. The test system was used to evaluate and compare refrigerant alternatives for both medium- and low-temperature systems.

The data obtained from the test site permits efficiency comparisons for each refrigerant under “real” commercial system conditions. Actual food display fixtures operated in an environmentally controlled space, with a refrigerant compressor equipped with variable speed drive used to simulate the various volume displacements required by different refrigerants. Test runs compared “baseline” CFC refrigerants with interim HCFC blends and HFC (zero chlorine) azeotrope and zeotropes blends.

The test set-up included a heat rejection chiller which provided the capability to operate from 120 F to 40 F condensing temperature. Extensive instrumentation acquired data over a range of condensing temperatures as well as establishing the effects of variable speed and return gas temperature for normalization of test results.

The refrigerants that were tested are listed in the table below:

Tested Refrigerants

CFCs HCFCs HFCs

R-12 R-22 R-134a R-502 R-401A (SUVA MP39) R-404A (SUVA HP62) R-402A (SUVA HP80) R-507 (AZ-50) R-408A (FX-10) R-407A (KLEA 60) R-407C (KLEA 66) R-410A (AZ-20)

Efficient Technologies for Commercial Refrigeration 141 Description of the Test Facility

The Commercial Refrigeration/CFC Demonstration Project test facility is owned by Southern California Edison Co. (SCE). The original project equipment was housed in a temporary building on a pad provided by SCE and was located at SCE’s Highgrove Facility in Colton, California. (The project has since been moved to SCE’s Customer Technology Center in Irwindale, California.)

Construction began in October, 1993 and was completed in January, 1994. Initial test runs began in February, 1994 and were completed in September, 1994. A subsequent test was run in October 1995 for R-408A.

The interior of the temporary building was divided into two areas, separated by an insulated partition. At one end of the building, an area of approximately 14' W x 24' L was maintained as a “controlled environment,” and housed the supermarket cooler and freezer display case fixtures. The remaining area provided space for the systems refrigeration equipment, data acquisition system scanners, and the man-machine interface computer.

142 Efficient Technologies for Commercial Refrigeration

“Advanced” System Test Configuration (Liquid Subcooling with TES)

Review of Test System Components

The test system components included:  Refrigerant test compressor rack  TES simulation chiller rack  Control system  Other compressor system materials

Efficient Technologies for Commercial Refrigeration 143 Test Runs

Twelve refrigerants were tested, as shown in the table “Tested Refrigerants and Sequence of Testing.” All runs with CFC and HCFC refrigerants were performed using the alkyl-benzene (AB) lubricating oil installed at start-up. Before installing and testing the HFC refrigerants, the AB oil was removed from the system by successive draining and flushing with the new ester oil. Laboratory testing of oil samples verified a concentration of AB oil of less than 1%.  Refrigerant Change-Over(s): The refrigerants were removed and installed as follows:  The entire system was leak tested.  Refrigerants were removed from the test rack using a combination of liquid and vapor recovery methods.  Drier block was changed. The entire test system was evacuated to 200 microns or less. The test rack was charged with the new refrigerant, and manufacturers’ recommendations for blends were followed to ensure that proper mixture fractions were maintained.  Test Run Sequence: A typical test run required 24 to 48 hours of continuous data collection. The test run sequence normally occurred on a 6-to-10 day cycle, shown in the table below.

Test Run Sequence

Day 1: Start system, balance valves, and begin data collection. Day 2: Review first day of data. If good, continue run. Day 3: Review data run. If complete, proceed; if not, re-run test. Day 4: Perform speed and return gas temperature tests; continue review of test run data. Day 5: When all tests have been completed, remove and reinstall refrigerant. Days 6 - 10: Start-up with new refrigerant, adjust settings, verify operations required, etc.

144 Efficient Technologies for Commercial Refrigeration Test Result Tables

The results of refrigerants testing are shown in the following tables. Using classical error analysis methods, the maximum error of the numbers in these tables is 1.5%.

Test Results 1 Medium-Temperature Efficiency Comparison at Selected Saturated Condensing Temperatures (SCT) kW/Ton at 30 F Fixture Discharge Air Temperature

70 F SCT 90 F SCT 110 F SCT Refrigerant kW/ % vs. kW/ % vs. kW/ % vs. Ton R-12 Ton R-12 Ton R-12 R-12 0.88 1.16 1.48 R-22 (a) 0.79 -10.7% 1.11 -4.3% 1.50 1.7% R-401A (MP39) 0.90 2.2% 1.18 2.0% 1.53 3.6% R-134a 1.00 13.5% 1.25 8.4% 1.55 5.1% R-404A (a) 0.82 -6.6% 1.21 4.5% 1.70 17.8% (a) Note that R-404A and R-22 are higher pressure refrigerants than R-12, R-401A and R-134a.

Test Results 2 Low-Temperature Efficiency Comparison at Selected Saturated Condensing Temperatures (SCT) kW/Ton at -5 F fixture Discharge Air Temperature

70 F SCT 90 F SCT 110 F SCT Refrigerant kW/ % vs. kW/ % vs. kW/ % vs. Ton R-502 Ton R-502 Ton R-502 R-502 1.44 1.90 2.43 R-22 1.57 9.5% 2.12 12.0% 2.74 12.5% R-402A (HP80) 1.53 6.4% 2.11 11.3% 2.81 15.5% R-404A (HP62) 1.47 2.2% 2.04 7.6% 2.74 12.6% R-507 (AZ-50) 1.43 -0.7% 1.94 2.3% 2.56 5.4% R-407A (KLEA60) 1.55 7.8% 2.03 7.1% 2.59 6.4% R-407C (KLEA66) 1.61 12.0% 2.08 9.7% 2.61 7.3% R-410A (AZ-20) 1.35 -6.1% 1.80 -4.9% Low temperature R-22 results include the effect of liquid injection cooling at the compressor that may have had greater impact than in many actual systems. For comparison purposes, an average of bubble point and dew point was used as the comparison saturated condensing temperature for refrigerants that exhibit a temperature glide. Electronic expansion valves performed poorly with R-407A and R-407C due to temperature glide. Results would be somewhat better with proper valve control.

Efficient Technologies for Commercial Refrigeration 145 Within a year of completing the initial test runs, Elf-Atochem, a refrigerant manufacturer, was interested in a comparison of R-408A with R-502. Arranm out-performed R-502 by 7 or 8%. The other R-502 interim refrigerant tested (R-402A) had an energy increase of 6 to 15% over R-502. Prior to this test run, it was thought that most interim refrigerants for R-502 would have an increasing energy impact on the systems they were used in. This apparently is not the case.

Test Results 3 Low-Temperature Efficiency Comparison at Selected Saturated Condensing Temperatures (SCT) kW/Ton at -5 F fixture Discharge Air Temperature

70 F SCT 90 F SCT 110 F SCT Refrigerant kW/ % vs. kW/ % vs. kW/ % vs. Ton R-502 Ton R-502 Ton R-502 R-502 1.47 0.00% 1.95 0.00% 2.52 0.00% R-408A 1.35 -8.16% 1.80 -7.69% 2.33 -7.54% (Forane FX-10) For “glide” refrigerants, kW/ton results are adjusted to equate SCT to (dew point + bubble point)/2; October 25, 1995

In the preceding tables, the efficiency difference between refrigerants can be seen to change with changes in condensing temperature. In operation, most systems operate at varying condensing temperatures through the year.

Actual systems may include differences—pressure drops, effect of subcooling, suction line heat gain, floating head pressure, etc.—which would change the results indicated above. It should be noted that while some efficiency differences above are significant, system design can have a greater impact on efficiency than the choice of refrigerant.

Refrigerant Tables

On the following pages are tables that provide some information about common refrigerants.

146 Efficient Technologies for Commercial Refrigeration

502

502

-

-

22 and R and 22

22 and R and 22

-

-

502

-

temperature refrigeration temperature

-

12

12

-

-

and low and

-

12 compressors 12

-

502

22

12

Notes/Uses

-

-

-

502

502

502

-

-

-

502 medium 502

-

F; transition for R for transition F;

F; transition for R for transition F;





12 alternative 12

10

10

-

-

-

22 alternative; new installations new alternative; 22

conditions

22); needs compressor redesign; replacement for R for replacement redesign; compressor needs 22);

22); needs compressor redesign; replacement for R for replacement redesign; compressor needs 22);

-

-

-

12 transition 12

-

22

502 conditions; retrofit and new applications new and conditions; retrofit 502

-

-

123 replacement 123

-

502 and R and 502

-

conditioning; R conditioning;

-

ternative; transition for R for transition ternative;

term R term

-

pressure centrifugals; phase out begins in 1996, EOP 2030 EOP 1996, in begins out phase centrifugals; pressure

-

Sorted by ASHRAE Number ASHRAE by Sorted

—

Interim option; transition refrigerant for R for refrigerant transition option; Interim

Interim option; transition refrigerant for R for refrigerant transition option; Interim

High pressure (50% >R (50% pressure High

High pressure (50% >R (50% pressure High

Interim alternative; R alternative; Interim

Interim retrofit solution for R solution retrofit Interim

Close to existing R existing to Close

Close to existing R existing to Close

Mobile air Mobile

Interim option; transition refrigerant for R for refrigerant transition option; Interim

Long

Interim al Interim

Interim alternative; commercial, transport refrigeration; transition for R for transition refrigeration; transport commercial, alternative; Interim

Interim alternative; transition for R for transition alternative; Interim

Interim alternative; transition for R for transition alternative; Interim

Interim alternative below below alternative Interim

Interim alternative above above alternative Interim

Small refrigerators or industrial equipment industrial or refrigerators Small

Possible future R future Possible

First HFC; autos, chillers; new or retrofit R retrofit or new chillers; autos, HFC; First

Low critical temperature, which may limit use as a pure fluid pure a as use limit may which temperature, critical Low

Low

Mildly flammable Mildly

Phaseout starts 1996; EOP 2030 EOP 1996; starts Phaseout

Reciprocating compressors, some centrifugals; EOP 1995 EOP centrifugals; some compressors, Reciprocating

Most centrifugal compressors, chillers; End of Production (EOP) 1995 (EOP) Production of End chillers; compressors, centrifugal Most

44

0.35

0.33

0.4

0.

0.3

0.75

0.28

0.7

0.50

0.22

0.94

4.09

1.19

0.52

0.63

0.24

0.22

0.0

0.28

0.84

0.02

0.14

0.43

2.09

1.00

HGWP

5

ODP

0.037

0.03

0.0 0.0

0.0 0.0

0.05

0.024

0.0 0.0

0.0 0.0

0.060

0.024

0.0 0.0

0.033

0.041

0.033

0.022

0.038

0.036

0.0 0.0

0.0 0.0

0.0 0.0

0.0 0.0

0.02

0.0 0.0

0.055

1.0 1.0

1.0 1.0

Common Refrigerants Common

(propane series) (propane

2

(38/2/60)

Chemical

(propane)

hane series) hane

3

CHF

(ethane series) (ethane

-

(ethane series) (ethane

(ethane series) (ethane

2

3

3

3

(methane series) (methane

CH

(met

2

2

(methane series) (methane

CF

CF

2

Formula/Composition

-

CF

2

2

2

F

F (methane series) F (methane

CH

F

FCF

F

2

3

3

2

2

2

22/600a/142b (55/4/41) 22/600a/142b

22/152a/142b/C318 (45/7/5.5/42.5) 22/152a/142b/C318

125/143a/134a (44/52/4) 125/143a/134a

290/22/218 (5/56/39) 290/22/218

290/22/218 (5/75/20) 290/22/218

125/290/22 125/290/22

125/290/22 (60/2/38) 125/290/22

22/152a/124 (61/11/28) 22/152a/124

22/152a/124 (53/13/34) 22/152a/124

1270/22/152a (3/94/3) 1270/22/152a

1270/22/152a (1.5/87.5/11) 1270/22/152a

32/125 (45/55) 32/125

32/125 (50/50) 32/125

22/124/142b (60/25/15) 22/124/142b

125/143a/22 (7/46/47) 125/143a/22

32/125/134a (23/25/52) 32/125/134a

32/125/134a (10/70/20) 32/125/134a

-

-

-

-

-

-

-

-

-

-

-

-

-

-

-

-

-

R

R

R

R

R

R

R

R

R

R

R

R

R

R

R

R

R

CH

CH

CH

CHF

CHCl

CH

CHClF

CCl

CCl

Prefix

HCFC/HC

HCFC/HC

HFC

HFC

HCFC

HCFC/HFC

HFC

HFC

HCFC/HC

HCFC/HC

HFC

HCFC/HFC/HC

HCFC/HFC/HC

HCFC/HC/HFC

HCFC/HC/HFC

HCFC/HFC

HCFC/HFC

HC

HFC

HFC

HFC

HCFC

HFC

HCFC

CFC

CFC

Composition Composition

32

22

12

11

290

125

123

134a

411B

411A

410B

410A

409A

408A

407B

406A

405A

404A

403B

403A

402B

402A

401B

401A

407C

245ca ASHRAE Number

Efficient Technologies for Commercial Refrigeration 147

-

ively ively

all all

404A and R and 404A

-

industrial

without change change without

408A, R 408A,

-

systems systems

flammable and relat and flammable

-

.

402A/B, R 402A/B,

-

spheric lifetime; used in mobile mobile in used lifetime; spheric

toxic, non toxic,

-

temp refrigeration, DX residential and and residential DX refrigeration, temp

22, R 22,

-

-

medium temperature systems, no oil or or oil no systems, temperature medium

22 low temperature temperature low 22

to low to

-

-

ndustrial process refrigeration, refrigeration, process ndustrial

-

R

Manufacturer claims compatible with with compatible claims Manufacturer

22 systems 22

-

evaporator temperature evaporator

and

acceptable for use in new and retrofit equipment as as equipment retrofit and new in use for acceptable

22 in low in 22

502, also for R for also 502,

-

-

R

502

ditioning; suitable for low, medium, and high evaporator evaporator high and medium, low, for suitable ditioning;

502; 502;

-

-

407C,

-

Notes/Uses

417A, R 417A,

-

, R

; Carbon dioxide is low in cost, non cost, in low is dioxide Carbon ;

temperature

-

502

-

low

DX water chillers, DX medium DX chillers, water DX

-

R

primarily replacement for replacement primarily

possible refrigerating capacity losses. capacity refrigerating possible

primarily a replacement for R for replacement a primarily

22, R402A, R402B, and R408A in chillers, i chillers, in R408A and R402B, R402A, 22,

mmercialized

-

applications designed to replace R replace to designed applications

replacement for replacement

for R for

Sorted by ASHRAE Number (continued) Number ASHRAE by Sorted

12 alternative; EPA SNAP acceptance for flooded evaporators; used in mobile and stationary stationary and mobile in used evaporators; flooded for acceptance SNAP EPA alternative; 12

12 alternative; used only in stationary applications stationary in only used alternative; 12

500 alternative; ultra alternative; 500

temperature applications temperature

-

-

-

-

ermediate blend; ermediate

—

nt

ntermediate blend; lubricant MO, AB or POE; applications include retrofits for DX water chillers, chillers, water DX for retrofits include applications POE; or AB MO, lubricant blend; ntermediate

reactive.

-

12 alternative; as sold, is not legal in the U.S. because of too long atmo long too of because U.S. the in legal not is sold, as alternative; 12

FC intermediate blend; primarily replacement for R for replacement primarily blend; intermediate FC

-

non

Industrial compressors, heat pumps heat compressors, Industrial

Industrial compressors Industrial

Very low Very

New or retrofit or New

Used in reciprocating compressors in food service; EOP 1995 EOP service; food in compressors reciprocating in Used

Centrifugal chillers, heat pump water heaters water pump heat chillers, Centrifugal

commercial air conditioning air commercial

component changes required. required. changes component

HFC i HFC

process air conditioning, retail food refrigeration, cold storage warehouses, and more and warehouses, storage cold refrigeration, food retail conditioning, air process

a substitute a

Intermediate blend; Intermediate

standard equipment components and materials used in R in used materials and components equipment standard

of lubricant type, but but type, lubricant of

temperature; temperature;

commercial and industrial DX refrigeration, air con air refrigeration, DX industrial and commercial

HFC i HFC

industrial DX refrigeration; suitable for low and medium and low for suitable refrigeration; DX industrial

507; lubricant MO, AB or POE; applications include new equipment and retrofits for commercial and and commercial for retrofits and equipment new include applications POE; or AB MO, lubricant 507;

H

applications

Interim R Interim

Not likely to be co be to likely Not

Interim R Interim

and stationary applications in Europe in applications stationary and

R

Interim R Interim

0

0

4.1

0.98

3.75

~0.56

~0.65

~0.52

~0.65

~0.2

~0.3

~1.0

HGWP

ODP

0.0

0.0 0.0

0.2 0.2

0.0 0.0

0.180

0.545

0

0

0

0

0.01

0.044

0.0

0.052

)

Common Refrigerants Common

600a 600a

-

.2)

One Shot One

600

-

142b/R

-

152a (5/80/15) 152a

-

218/R600a 218/R600a

-

Chemical

22/R

124/R

-

-

(carbon dioxide) (carbon

ammonia

22B, ICOR XAC1 ) XAC1 ICOR 22B,

-

-

2

3

rmula/Composition

23/116 (39/61) 23/116

125/143a (45/55) 125/143a

22/115 (48.8/51.2) 22/115

12/152a (73.8/26 12/152a

125/R134a/R600a 125/R134a/R600a

125/R134a/R600a 125/R134a/R600a

125/R134a/R600a 125/R134a/R600a

125/R134a/R600a 125/R134a/R600a

134a/R124/R

23/R

22/R

134a/R

22/218/142b (70/5/25) 22/218/142b

-

-

-

-

-

-

-

-

-

-

-

-

-

ICOR XLT1) ICOR

CO

NH

R

R

R

R

(ISCEON MO29) (ISCEON

(65.1/31.5/3.4)

R

(

(82.0/15.0/3.0) (82.0/15.0/3.0)

R

(NU

(55.0/42.0/3.0)

R

(ISCEON MO79, MO79, (ISCEON

(85.1/11.5/3.4)

R

(59/39/2)

R

R

(50/39/9.5/1.5)

R

(88/9/3)

R

R

Fo

Prefix

--

IC

HFC

HFC

CFC/HCFC

CFC/HFC

HFC/HC

HFC/HC

HFC/HC

HFC/HC

HCFC

HCFC

HCFC

HFC

HCFC/HFC

Composition

744

717

507

502

500

Note: The information is derived from various sources. Verify accuracy with refrigerant manufacturers. refrigerant with accuracy Verify sources. various from derived is information The Note:

508A

422B

422A

416A

415A

414B

413A

412A

422D

422C ASHRAE Number

148 Efficient Technologies for Commercial Refrigeration

ass**

/1000

/1000

/1000

/840

/800

A1/1000

A1/1000

A1/1000

A2

A1

A1

A1

A1

A1

A1

A1

A1

A3/1000

A1/1000

A1/1000

B1/30

A2/1000

A1/1000

A1/1000

A1/1000

Toxicity Limit Toxicity

Safety Cl Safety

15.1

18.5

309.7

302.8

325.2

180.0

165.9

228.4

171.1

344.6

429.5

260.0

157.3

261.7

319.0

285.3

psig at 120°F at psig

20°F

psig at at psig

36.9

52.9

42.8

55.5

53.5

59.3

21.5

18.1

41.2

18.4

63.8

22.8*

43.1

21.1

21.1*

80

Saturation Pressures Pressures Saturation

30°F

1.5

7.3

3.5

9.9

8.9

7" vac 7"

9" vac 9"

5.7

9.8*

4.9

5.5*

-

psig at at psig

11.3

12.8

28.3*

18.2

27.8*

ODP

0.0 0.0

0.0 0.0

0.0 0.0

0.06

0.024

0.0 0.0

0.033

0.041

0.033

0.022

0.038

0.036

0.0 0.0

0.0 0.0

0.0 0.0

0.0

0.02

0.0 0.0

0.055

1.0 1.0

1.0 1.0

Sorted by ASHRAE Number ASHRAE by Sorted

—

F

F

F

F

F

F

F

F

F

F

F

F

F

F

F

F

F

F

F

high

high

6° 6°

1° 1°

2° 2°

4° 4°

3° 3°

3° 3°

9° 9°

9° 9°

0° 0°

0° 0°

0° 0°

0° 0°

0° 0°

0° 0°

0° 0°

0°

0°

Glide Glide

11° 11°

10° 10°

(approx.)

Evaporative

36° F 36°

45° F 45°

38° F 38°

50° F 50°

53° F 53°

19° F 19°

16° F 16°

-

-

-

-

-

-

-

F

F

F

F

F

F

F

F

F

F

F

F

Range

Refrigerant Properties Refrigerant

(approx.)

5° 5°

49° to to 49°

53° to to 53°

49° to to 49°

26° to ? F ? to 26°

17.1° F 17.1°

52° 52°

59° 59°

58° 58°

53° to to 53°

56° to to 56°

30° to 30°

27° to to 27°

44° 44°

77° 77°

1

55° 55°

82° 82°

61° 61°

41° 41°

22° 22°

75° 75°

Boiling Point/ Boiling

-

-

-

-

-

-

-

-

-

-

-

-

-

-

-

-

-

-

d

opic Blend opic

or Blend or

Pure Compound Pure

Zeotropic Blend Zeotropic

Zeotropic Blend Zeotropic

Zeotropic Blend Zeotropic

Zeotropic Blend Zeotropic

Zeotropic Blend Zeotropic

Zeotropic Blend Zeotropic

Zeotr

Zeotropic Blend Zeotropic

Zeotropic Blend Zeotropic

Zeotropic Blend Zeotropic

Zeotropic Blend Zeotropic

Zeotropic Blend Zeotropic

Pure Compound Pure

Pure Compound Pure

Pure Compound Pure

Pure Compound Pure

Pure Compound Pure

Pure Compound Pure

Pure Compoun Pure

Pure Compound Pure

Pure Compound Pure

32

22

12

11

290

125

123

134a

407B

407A

406A

405A

404A

403B

403A

402B

402A

401B

401A

407C

245ca

Number ASHRAE

Efficient Technologies for Commercial Refrigeration 149

/1000

/1000

/1000

A1/1000

B2/25

A1/1000

A1/1000

A1/1000

A1/1000

A1/1000

A1/1000

A1/1000

A1/1000

A1

A2

A1

A2

A2

A2

A2

A1

A1

A1

A1

Toxicity Limit Toxicity

Safety Class** Safety

97

271.9

321.

282.72

151.0

185.0

196.0

255.0

243.0

416.0

171.1

286.8

psig at 120°F at psig

20°F

psig at at psig

33.5

57.624

52.5

14.3

24.3

25.3

43.0

39.0

79.0

18.5

49.5

425 psia 425

Saturation Pressures Pressures Saturation

30°F

1.6*

9.2

2.5

1.0

0.8

4.9

3.6

9.9

7.6

-

psig at at psig

10.3

18.0

175 psia 175

@ 140° F, 328 psig F, 328 @ 140°

Vapor pressure @ 68° F, 116 psig; F, 116 @ 68° pressure Vapor

vapor pressure @ 77° F, 185 psia F, 185 @ 77° pressure vapor

ODP

0.0

0.0 0.0

0.0 0.0

0.0 0.0

0.23

0.545

0.0

0.0

0.0

0.0

0.01

0.044

0.0

0.52

0.45

0.42

0.0 0.0

0.0 0.0

0.05

0.024

(ppm) AEL or other AEL (ppm)

**

F

F

F

F

F

F

Sorted by ASHRAE Number ASHRAE by Sorted

F

F

F

F

F

F

F

F

F

F

—

.0° .0°

.0° .0°

.0° .0°

0°

0°

0°

0°

0°

0°

7

8

3

5.0° 5.0°

7.0° 7.0°

0°

0°

1°

Glide Glide

16.0° 16.0°

12°

(approx.)

Evaporative

7° F 7°

14° F 14°

18° F 18°

15° F 15°

F

-

-

-

-

F

F

F

F

F

to to

Range

(approx.)

Refrigerant Properties Refrigerant

Boiling Point/ Boiling

28° F 28°

51° F 51°

50° F 50°

28° F 28°

46° F 46°

50° F 50°

41° F 41°

52° F 52°

11° to to 11°

30° to to 30°

31° to to 31°

37°

41°

39°

61°

62.5° 62.5°

30°

46°

-

-

-

-

-

-

-

-

-

-

-

-

-

-

-

-

-

-

109° F 109°

122° F 122°

-

-

or Blend or

Pure Compound Pure

Inorganic Compound Inorganic

Inorganic Compound Inorganic

Azeotropic Blend Azeotropic

Azeotropic Blend Azeotropic

Azeotropic Blend Azeotropic

Azeotropic Blend Azeotropic

Zeotropic Blend Zeotropic

Zeotropic Blend Zeotropic

Zeotropic Blend Zeotropic

Zeotropic Blend Zeotropic

Zeotropic Blend Zeotropic

Zeotropic Blend Zeotropic

Zeotropic Blend Zeotropic

Zeotropic Blend Zeotropic

Zeotropic Blend Zeotropic

Zeotropic Blend Zeotropic

Zeotropic Blend Zeotropic

Zeotropic Blend Zeotropic

Zeotropic Blend Zeotropic

Zeotropic Blend Zeotropic

Zeotropic Blend Zeotropic

e information is derived from various sources. Verify accuracy with refrigerant manufacturers. refrigerant with accuracy Verify sources. various from derived is information e

Inches Hg Vacuum Hg Inches

Note: Th Note:

744

717

508A

507

502

500

412A

411B

411A

410B

410A

409A

408A

422D

422C

422B

422A

416A

415A

414B

413A

Number

ASHRAE *

150 Efficient Technologies for Commercial Refrigeration Zeotropes 400 R-12/114 (must be specified) (50.0/50.0), (60.0/40.0) 401A R-22/152a/124 (53.0/13.0/34.0) 401B R-22/152a/124 (61.0/11.0/28.0 401C R-22/152a/124 (33.0/15.0/52.0) 402A R-125/290/22 (60.0/2.0/38.0) 402B R-125/290/22 (38.0/2.0/60.0) 403A R-290/22/218 (5.0/75.0/20.0) 403B R-290/22/218 (5.0/56.0/39.0) 404A R-125/143a/134a (44.0/52.0/4.0) 405A R-22/152a/142b/C318 (45.0/7.0/5.5/42.5) 406A R-22/600a/142b (55.0/4.0/41.0) 407A R-32/125/134a (20.0/40.0/40.0) 407B R-32/125/134a (10.0/70.0/20.0) 407C R-32/125/134a (23.0/25.0/52.0) 407D R-32/125/134a (15.0/15.0/70.0) 407E R-32/125/134a (25.0/15.0/60.0) 407F R-32/125/134a (30.0/30.0/40.0) 408A R-125/143a/22 (7.0/46.0/47.0) 409A R-22/124/142b (60.0/25.0/15.0) 409B R-22/124/142b (65.0/25.0/10.0) 410A R-32/125 (50.0/50.0) 410B R-32/125 (45.0/55.0) 411A R-1270/22/152a) (1.5/87.5/11.0) 411B R-1270/22/152a (3.0/94.0/3.0) 412A R-22/218/143b (70.0/5.0/25.0 k 413A R-218/134a/600a (9.0/88.0/3.0) 414A R-22/124/600a/142b (51.0/28.5/4.0/16.5) 414B R-22/124/600a/142b (50.0/39.0/1.5/9.5) 415A R-22/152a (82.0/18.0) 415B R-22/152a (25.0/75.0) 416A R-134a/124/600 (59.0/39.5/1.5) 417A R-125/134a/600 (46.6/50.0/3.4) 417B R-125/134a/600 (79.0/18.3/2.7) 417C R-125/134a/600 (19.5/78.8/1.7) 418A R-290/22/152a (1.5/96.0/2.5) 419A R-125/134a/E170 (77.0/19.0/4.0) 419B R-125/134a/E170 (48.5/48.0/3.5) 420A R-134a/142b (88.0/12.0) 421A R-125/134a (58.0/42.0) 421B R-125/134a (85.0/15.0) 422A R-125/134a/600a (85.1/11.5/3.4) 422B R-125/134a/600a (55.0/42.0/3.0) 422C R-125/134a/600a (82.0/15.0/3.0)

Efficient Technologies for Commercial Refrigeration 151 422D R-125/134a/600a (65.1/31.5/3.4) 422E R-125/134a/600a (58.0/39.3/2.7) 423A 134a/227ea (52.5/47.5) 424A R-125/134a/600a/600/601a (50.5/47.0/0.9/1.0/0.6) 425A R-32/134a/227ea (18.5/69.5/12) 426A R-125/134a/600/601a (5.1/93.0/1.3/0.6) 427A R-32/125/143a/134a (15.0/25.0/10.0/50.0) 428A R-125/143a/290/600a (77.5/20.0/0.6/1.9) 429A R-E170/152a/600a (60.0/10.0/30.0) 430A R-152a/600a (76.0/24.0) 431A R-290/152a (71.0/29.0) 432A R-1270/E170 (80.0/20.0) 433A R-1270/290 (30.0/70.0) 433B R-1270/290 (5.0/95.0) 433C R-1270/290 (25.0/75.0) 434A R-125/143a/134a/600a 435A R-E170/152a (80.0/20.0) 436A R-290/600a (56.0/44.0) 436B R-290/600a (52.0/48.0) 437A R-125/134a/600/601 (19.5/78.5/1.4/0.6) 438A R-32/125/134a/600/601a (8.5/45.0/44.2/1.7/0.6) 439A R-32/125/600a (50.0/47.0/3.0) 440A R-290/134a/152a (0.6/1.6/97.8) 441A R-170/290/600a/600 (3.1/54.8/6.0/36.1) 442A R-32/125/134a/152a/227ea (31.0/31.0/30.0/3.0/5.0) 443A R-1270/290/600a (55.0/40.0/5.0) 444A R-32/152a/1234ze(E) (12.0/5.0/83.0) 445A R-744/134a/1234ze(E) (6.0/9.0/85.0) Azeotropes 500 R-12/152a (73.8/26.2) 501 R-22/12 (75.0/25.0) 502 R-22/115 (48.8/51.2) 503 R-23/13 (40.1/59.9) 504 R-32/115 (48.2/51.8) 505 R-12/31 (78.0/22.0) 506 R-31/114 (55.1/44.9) 507A R-125/143a (50.0/50.0) 508A R-23/116 (39.0/61.0) 508B R-23/116 (46.0/54.0) 509A R-22/218 (44.0/56.0) 510A R-E170/600a (88.0/12.0) 511A R-290/152a (95.0/5.0) 512A R-134a/152a (5.0/95.0)

152 Efficient Technologies for Commercial Refrigeration Methods For Improving Refrigeration System Efficiency

The performance and energy consumption of refrigeration systems is directly related to the difference in pressure between the evaporator and the condenser, which indicates the amount of pressure the compressor needs to work against.

System efficiency can be improved by adjusting pressure to increase the “refrigeration effect” and reducing compressor horsepower requirement. Two ways to minimize “lift,” which is the difference between the suction and discharge pressures, are:  Increasing evaporator pressure (the higher the better to optimize system performance)  Decreasing condenser pressure

System efficiency can be improved by adjusting temperature:  Increasing the refrigerant suction temperature  Decreasing temperature of the liquid line refrigerant  Decreasing the condensing temperature

In this section, we’ll begin with a brief physics lesson, then discuss the main ways refrigeration systems can improve energy efficiency:  Reducing flash gas  Subcooling  Floating head pressure  Floating suction pressure  Energy management systems (EMS)

Other ways refrigeration systems can improve energy efficiency that we discussed earlier include:  BLDC (or EC) motors  Energy efficient case lighting  Door closers  Improved defrost methods  Case covers

Efficient Technologies for Commercial Refrigeration 153 A Brief Physics Lesson...

In this brief physics lesson we will use two types of diagrams to study a little about the physics of refrigerants and how they behave when used in the refrigeration cycle:  Pressure-Enthalpy diagrams.  Cycle diagrams.

To the left is a Refrigerant Properties table for R- 134a. This type of table provides data about the properties of a refrigerant.

The table includes values for temperature, pressure, specific volume, enthalpy, and more. The table at the left is a partial table—“full” tables provide additional data.

If you know a single value, you can use this kind of table to look up other corresponding data.

For example, if you want to maintain a temperature of 25 F, what would the pressure be?

If you plot the data found on a Refrigerant Properties Table, the result is a Pressure-Enthalpy diagram shown on the following page.

The data in a Refrigerant Properties table will vary for each individual refrigerant. It follows that the corresponding Pressure-Enthalpy diagrams for specific refrigerants will also vary.

Refrigerant properties table for R-134a

154 Efficient Technologies for Commercial Refrigeration

Efficient Technologies for Commercial Refrigeration 155 Pressure-Enthalpy Diagram

All refrigerants have certain thermodynamic properties. (Thermodynamics is the “physics that deals with the mechanical actions or relations of heat.”)

The Pressure-Enthalpy diagram of a refrigerant, shown on the facing page, presents graphically the properties of a refrigerant.

The Pressure-Enthalpy diagram is used to:  Represent the condition of the refrigerant in any thermodynamic state as a point on the diagram.  Analyze refrigeration system performance.

All refrigerants have similar thermodynamic, transport, and heat transfer characteristics, but the specific numerical values of the properties vary from one refrigerant to another. The diagram on the facing page is for R-134a.

In a Pressure-Enthalpy diagram:  The pressure the refrigerant is under is plotted along the vertical axis. Pressure is in psia = pounds per square inch absolute.  The enthalpy or “total heat content” in the refrigerant is plotted along the horizontal axis. Enthalpy is measured in Btu per pound. (British Thermal Units is the amount of heat energy required to raise the temperate of one pound of water by 1 F at sea level.)

156 Efficient Technologies for Commercial Refrigeration Recall that when liquids are heated, they undergo a change of state or a phase change to a vapor (vaporization). Vapor that is cooled will change state back to a liquid (condensation).

The term saturated means that a refrigerant is at a temperature and pressure at which the phase change between liquid and vapor will occur.

Saturated liquid: when the temperature of a liquid is raised to the point where any additional heat is added and will cause it to vaporize, the liquid is said to be saturated.

The temperature where liquid vaporizes when heat is added is called the saturation temperature of a liquid.

Saturated vapor: a vapor is called a saturated vapor as long as its temperature and pressure are the same as those of the saturated liquid that it came from.

The saturation temperature of a vapor is the temperature at which the liquid will condense to a liquid state if heat is removed. In other words, if you cool a saturated vapor, some of the vapor will condense.  The saturation temperature of the liquid and of the vapor are the same for any given pressure.  Liquid will vaporize at any temperature above its saturation temperature and vapor will condense to liquid at any temperature below its saturation temperature.

Saturated liquid is all liquid; saturated vapor is all vapor.

The latent heat of vaporization is the amount of energy the refrigerant will absorb or release during a phase change between liquid and gas.

Enthalpy, measured in Btu/lb, is the heat of fusion or vaporization whichever is applicable. So, the enthalpy value may be for saturated liquid, for vaporization, for saturated vapor, or for superheated vapor, or any mix of liquid and vapor.

Efficient Technologies for Commercial Refrigeration 157

The graphic above is a simplified version of the Pressure-Enthalpy diagram.  The curve in the diagram is called the saturation line.  To the right of the saturation line is the superheated region. The refrigerant is in the form of a superheated vapor. A superheated vapor is a vapor at any temperature above its saturation temperature.  To the left of the saturation line is the subcooled region. The refrigerant is in the form of a subcooled liquid. A subcooled liquid has been cooled to the point where its temperature is below the saturation temperature.  Under the saturation line is the region of phase change or the “two-phase” region. In this area, the refrigerant is a mixture of vapor and liquid. This is where the phase change from a liquid to a vapor or from a vapor to a liquid happens.

In the region of phase change, the percentages of vapor and liquid change as you move horizontally across the diagram.  The farther to the right under the curve, the greater the percentage of vapor; the farther to the left, the greater the percentage of liquid.  For example, in the middle under the curve the refrigerant is 50% liquid and 50% vapor; at a point near the vapor side of the saturation line it might be 95% vapor and 5% liquid; at a point near the liquid side of the saturation line it might be 5% vapor and 95% liquid.

158 Efficient Technologies for Commercial Refrigeration Cycle Diagram

The graphic on the left below is called a “cycle diagram.” It is a graphical representation of the standard vapor compression cycle (refrigeration cycle) superimposed onto a Pressure-Enthalpy diagram. A cycle diagram shows the different temperatures and pressures the refrigerant is under at the different points in the refrigeration cycle.

Cycle diagram Simple refrigeration cycle equipment

From 1 to 2: Refrigerant passes through the compressor; pressure rises; heat is added (the “heat of compression”)

From 2 to 3: Refrigerant passes through the condenser; heat is rejected by the condenser (the “heat of rejection”); pressure stays the same

From 3 to 4: Refrigerant passes through the expansion device; no energy change occurs (enthalpy or heat content remains the same); the pressure drops

From 4 to 1: Evaporation or the “cooling effect;” this is the heat removed from the space, which equals the heat that is absorbed by the evaporator; pressure stays the same; heat increases

Efficient Technologies for Commercial Refrigeration 159

Shown above is an example of a cycle diagram. It demonstrates how using the refrigeration cycle and Pressure-Enthalpy diagram, and given the tons of refrigeration, the type of refrigerant, and the condensing and evaporating temperatures, engineers can determine specific values in a system such as:  The refrigerating effect  The circulation rate of the refrigerant  The power required by the compressor (horsepower)  The coefficient of performance  The volume flow  The power per ton

The Pressure-Enthalpy diagrams (and the corresponding Refrigerant Properties tables) provide data that can be used in calculating these values.

160 Efficient Technologies for Commercial Refrigeration Condensate Flashing (Flash gas) or Incomplete Condensing

A source of inefficiency in refrigeration systems is when condensed liquid refrigerant (condensate) prematurely phase changes to a gas before it reaches the expansion valve or the evaporator. There are two ways this occurs in a refrigeration system and they both have the same result in the system:  Incomplete condensing—this is when the refrigerant in the condenser does not completely condense to liquid.  “Flashing” or “flash gas” refer to condensed liquid refrigerant that has evaporated too soon; it has gone through a phase change to gas prior to reaching the expansion valve or prior to entering the evaporator (at “D” in the diagrams below). This is refrigerant that has evaporated usually from an excessive pressure drop in the liquid line between the condenser and evaporator.

Early flashing of liquid refrigerant implies that refrigerant absorbs heat that would otherwise be absorbed from the evaporator. Low pressure flash gas is useless because it has gone through a phase change prematurely. Also, refrigerant gas that enters the evaporator inhibits the flow of liquid refrigerant and does little heat absorption.

In well-designed systems, flashing does not occur. But very few systems are truly well designed, so technologies that address this problem should be of interest in the refrigeration industry. A solution for incomplete condensing and flash gas is to raise the head pressure by controlling condenser heat rejection (i.e., reduce condenser air flow). However, this does increase energy use.

Note that a “fixed” head pressure assures complete condensing of the refrigerant as a liquid through the expansion valve. Incomplete condensing and flash gas are risks of implementing floating head pressure, which is discussed elsewhere.

D

Cycle diagram Simple refrigeration cycle equipment

Efficient Technologies for Commercial Refrigeration 161 Subcooling

Subcooling refers to the additional “cooling” of the refrigerant in the liquid line by outside air or an external refrigeration system. (The temperature is lowered to below the “saturated temperature,” or the point at which the refrigerant changes from liquid to gas). In other words, subcooling actually refrigerates the refrigerant.

The purpose of subcooling is to provide more cooling capacity. Subcooling is more commonly used with low-temperature systems, but it provides benefits for both low-temperature and medium- temperature applications, in particular by allowing reliable floating head pressure.

There are four reasons to implement subcooling:  Provides stable operation  Enables floating head pressure  Shifts load  Increases capacity

Subcooling provides several benefits:  Improves system efficiency by providing more cooling capacity (increases the refrigerating effect). Because the liquid entering the evaporator has been cooled, it has a much lower enthalpy content which gives the refrigerant a greater ability to absorb and remove heat.  Prevents condensate flashing, which facilitates floating head pressure by allowing expansion valves to function properly.  Decreases electricity use.  Gives better temperature control at the food cases.

Built-in subcooling (when no receiver tank)

Additional subcooling

Condenser

)

a i

s Refrigerating effect

p

(

e Increase in r

u refrigerating effect

s

s

e

r P

Enthalpy (Btu/lb) Heat removal

162 Efficient Technologies for Commercial Refrigeration When is subcooling applied?  When the efficiency of the refrigeration system with subcooling will be greater than the efficiency of the original system.  In any refrigeration process where additional capacity is required.  When operating costs must be reduced.  With some of the newer refrigerants:  Some of the newer refrigerants don’t carry heat as efficiently which means there is a loss of cooling capacity.  If subcooling is added to the system, it will regain some or all of the lost capacity, and provide a more efficient system.  For HCFCs (such as R-22), subcooling provides up to 20% more cooling capacity. For HFCs (such as R-404A or R-507), subcooling provides up to 40% more cooling capacity.

Where is subcooling applied?  Mechanical subcooling can be added to existing systems or designed into new ones.  Supermarket systems where present capacity is at a maximum or where new refrigeration cases are being installed.  Warehouse or processing applications to handle new load requirements or expansion of the facilities.  Industrial applications where additional capacity is needed to accommodate changes in product or additional equipment.  When overall system efficiency is needed in order to reduce operating costs.

How is subcooling applied?

There are several basic methods:  Liquid to suction subcooling  Mechanical subcooling (using a second compressor)  Ambient subcooling

Efficient Technologies for Commercial Refrigeration 163 Liquid To Suction Subcooling

Liquid to suction subcooling takes cool suction gas (vapor) from the evaporator to cool the liquid refrigerant line in a liquid-to-suction heat exchanger. Liquid to suction subcooling “stabilizes” the refrigeration system.

As with refrigerant subcooling, this method by itself does not provide substantial improvement in system efficiency. But like refrigerant subcooling, when used with floating head pressure, an increase in system efficiency can be realized.

The subcooling heat exchanger is installed between the receiver tank and the evaporator. The refrigerant temperature in the liquid line is reduced to below the saturated temperature, or the exact point at which the refrigerant changes from liquid to gas.

164 Efficient Technologies for Commercial Refrigeration Mechanical Subcooling

Mechanical subcooling refers to the use of liquid refrigerant or the use of a secondary compressor to partially cool the hot liquid refrigerant returning from the condenser before going to display fixtures, which reduces the work of the main compressor rack. Mechanical subcooling can provide a substantial improvement in system efficiency.

Parallel rack systems may include liquid subcooling, using a high temperature system to increase efficiency of low and medium temperature racks.

Mechanical subcooling can be added to existing systems or designed into new ones.  It can be applied in situations where more capacity is needed, or simply for reduced operating costs.  The investment in subcooling can provide a quick payback period from reduced energy costs. Also, for new systems, compressors and control valves can be smaller.

Most new construction includes subcooling since it is usually cost effective by reducing overall compressor size. Subcooling can be added to existing parallel racks. Mechanical subcooling produces maximum benefit during high ambient periods.

A major advantage of mechanical subcooling is its ability to allow for floating compressor head pressure. Floating the head pressure is only possible with subcooling.

Subcooling system (using a secondary compressor)

Efficient Technologies for Commercial Refrigeration 165 Mechanical and liquid to suction subcooling

This diagram demonstrates subcooling in multiple compressor system.  There is a liquid to suction subcooler.  Also, a two-stage mechanical liquid subcooler is present in this system.  With this configuration, the condenser also could provide ambient subcooling.

Subcooling in Multiple Compressor System

166 Efficient Technologies for Commercial Refrigeration The graphic below demonstrates how some new screw compressors can facilitate subcooling through an economizer suction port.

Semi-hermetic screw compressor with economizer

Vapor injection has been available on large commercial screw and multi-stage centrifugal compressors for many years. Fairly recently, individual, small vapor-injected scroll compressors were introduced into the market that can also take advantage of the economized refrigeration cycle and reap the benefits of increased capacity and efficiency. Vapor injected scroll compressors can be applied in various commercial refrigeration applications.

Ambient Subcooling

Ambient subcooling refers to passing the liquid refrigerant through the ambient air to reduce the liquid refrigerant temperature. This method applies in climates where the outside ambient temperature is below 50° F.

Parallel rack systems may include liquid subcooling by addition of a separate condenser circuit or by using a surge receiver.

Ambient subcooling is only beneficial on systems that cannot float head pressure. Ambient subcooling produces no benefit during high temperatures.

Efficient Technologies for Commercial Refrigeration 167 Ways to Save Energy

Two ways to save on energy costs with commercial refrigeration are referred to as floating head pressure and floating suction pressure.

As we have seen, refrigeration system efficiency can be improved by adjusting pressure to increase the “refrigeration effect” and reducing compressor horsepower requirement. One goal is to minimize “lift,” which is the difference between the suction and discharge pressures.

100

70

High Temperature 20 System

Low Temperature System

Evaporator / Condensing Temp Condensing / Evaporator -20

Cooling system “lift”

100 Floating Head 70 High Temperature System Low Temperature 20 System Floating Suction

Evaporator / Condensing Temp Condensing / Evaporator -20 Floating Suction

Reduced lift at non-peak, part load

168 Efficient Technologies for Commercial Refrigeration Floating Head Pressure

Floating head pressure refers to increasing and decreasing or “floating” the compressor/condenser head or discharge pressure.

Floating head pressure is:  A simple concept  Usually the largest energy saving opportunity  Not given sufficient attention during original design, during start-up, or during ongoing maintenance

Floating head pressure requires a little technology during design, and continuing understanding and attention by maintenance personnel.

In a refrigeration system, high pressure refrigerant gas passes through the condenser, and it is cooled by some external means. It can be air-cooled or water-cooled. The condenser is used to discharge the heat absorbed by the refrigerant in the evaporator and any heat added by the heat of compression.

Condensers used in refrigeration systems were intentionally designed to maintain a “fixed” head pressure that is high enough to achieve condensation under the worst possible (hottest) ambient conditions. The “fixed” high pressure in the liquid line is designed to prevent flash gas. This traditional approach means that the condenser pressure and temperature are too high during mild and cool weather.

100 90 Condensing temperature 80 70 60 50 Ambient dry bulb temperature 40 30 20 10 0 Jan Feb Mar Apr May Jun Jly Aug Sep Oct Nov Dec

Fixed head pressure Ambient DBT Condensing Temperature

Efficient Technologies for Commercial Refrigeration 169 The figure below represents a system controlled with a fixed head pressure setting equivalent to 85° F SCT.

Typical fixed head pressure system:  Sensors used to detect liquid line pressure.  The fixed controller maintains the pressure at 180 psi (+/- 2 psi)  The fan is cycled on/off based on the pressure reading.

Fixed head pressure configuration

170 Efficient Technologies for Commercial Refrigeration Floating head pressure takes advantage of lower outdoor temperatures.  As outdoor temperatures go lower, the compressor head pressure can also be lowered. The lower the head pressure, the less the compressor needs to work (lower kW/ton at the compressor). Also, condensing temperatures are allowed to fluctuate with the changes in outdoor temperatures.  “Floating” the head pressure with changing ambient conditions improves system efficiency and reduces energy losses when compared with “fixed” head pressure control. More BTUs per hour are extracted out of the system without having to maintain a “false” head pressure (as designed for the “worst case” ambient conditions) to keep the system operating properly.

Floating head pressure reduces the amount of work the compressor must do during the majority of the time when outdoor temperatures are below the refrigeration system design temperature. This can provide energy savings for a majority of the year.

100 90 Condensing temperature 80 70 60 50 Ambient dry bulb temperature 40 30 20 10 0

Jan Feb Mar Apr May Jun Jly Aug Sep Oct Nov Dec Floating head pressure Ambient DBT Condensing Temperature

Efficient Technologies for Commercial Refrigeration 171 Floating head pressure control system:  Uses sensors to measure outdoor ambient temperature  Calculates and adjusts dampers, fans, etc., based on reading  Uses variable speed drive

Floating head pressure configuration

172 Efficient Technologies for Commercial Refrigeration The ALLS liquid to suction heat exchanger is a line stabilizer that facilitates floating head pressure.

A number of heat exchangers and related devices are marketed as energy saving tools. A representative selection, the Alco ALLS shown below is a heat exchanger that provides no energy savings by itself, but does facilitate savings through floating head pressure by maintaining vapor free liquid at the expansion valve inlet.

ALLS liquid to suction heat exchanger (Alco Controls)

Fixed vs. floating head operation

This graphic demonstrates the elevated pressure of a “fixed” system compared to the lower pressure of a “floating head” system. The “condenser line” will move up or down (floats) as the system requires relative to outdoor ambient temperature conditions.

As the pressure is reduced, there is less work for the compressor. From h1 to h3 represents higher head pressure (the compressor works harder). From h1 to h2 represents lower head pressure (less work for the compressor).

Efficient Technologies for Commercial Refrigeration 173

Variation of energy efficiency ratio with outdoor temperature (fixed head vs. floating head pressure)

174 Efficient Technologies for Commercial Refrigeration How to Measure Floating Head Pressure and Condensing Temperature Difference

Measuring floating head pressure and condensing temperature difference (TD) requires three steps: 1. Measure the ambient temperature. This includes dry bulb for air cooled condensers and wet bulb for evaporative cooled condenser. 2. Measure the condensing temperature. This is measured at the condenser outlet, or can be determined by converting the discharge pressure to saturation temperature, using a refrigerant chart. 3. Condensing temperature minus the ambient .

The TD should be:  For air-cooled low-temperature systems: between 8 to 12 degrees  For air-cooled medium-temperature systems: between 10 to 15 degrees  For evaporative-cooled medium-temperature systems: between 10 to 15 degrees  Or, running at the minimum condensing temperature, between 50 to 75 F

Efficient Technologies for Commercial Refrigeration 175 Benefits of Floating Head Pressure

Benefits of floating head pressure control in refrigeration applications:  Reduces power consumption for all refrigeration compressors in systems with either an evaporative or air-cooled condenser.  Can reduce supermarket refrigeration energy use 10 to 25%. For parallel systems, the way heat reclaim or gas defrost are implemented may limit how far head pressure can float.  Floating head pressure used with liquid subcooling overcomes the results of the pressure drop in the liquid line.  Preserves the high discharge temperatures needed for hot gas defrost (when required).

Energy savings result from:  Lower head pressure at the compressor (and lower condensing temperature at the condenser)  Lower condenser fan power through:  Variable speed  Variable setpoint  Potential savings with optimum floating head pressure:  12-20% of compressor and condenser energy  But, can be zero without proper control strategy

How To Control Head Pressure

There are several methods for controlling compressor head pressure. These methods require adjustments to the system or converting the system to accommodate microprocessor controls.

The valves that regulate refrigerant flow to the condenser must be adjusted or replaced and system controls must be changed.

These system changes allow the pressure and temperature of the refrigerant coming out of the compressor to rise and fall with changes in outdoor temperatures.

The controllers float the pressure down on days with milder temperatures, then allow for higher pressure on hotter days. They control and adjust:  Air-cooled condensers:  Air-side control (fans)  Dampers, variable speed, two speed, cycling, etc.  Water-cooled systems:  Fans  3-way valves

176 Efficient Technologies for Commercial Refrigeration Using Variable Speed Drives to Control Head Pressure

Variable speed drives (also called adjustable speed drives) are used in a variety of residential, industrial, commercial, and utility applications. These systems provide adjustable speed operation of motors that drive, for example, fans, blowers, compressors, and pumps for HVAC equipment, and other types of loads.

Variable speed drive systems take an alternating current with a fixed voltage and frequency, and change it into an alternating current with adjustable voltage and frequency. Motor speed can then be adjusted and coordinated to match exact process requirements.

Most commercial motors are 3-phase, AC induction motors that run at a fixed speed, or at a few fixed speeds. An adjustable AC voltage and frequency supply lets a motor operate at many different speeds with about the same performance as its base speed. Using a variable speed drive, AC motors can replace other types of variable speed equipment that may not be as cost effective or efficient.

These systems offer many benefits, including gains in system efficiency, precision, and reliability for greater productivity and/or improved product quality. They allow more efficient and effective use of electric power and, as a result, lower energy costs, extend equipment life, and reduce maintenance costs.

Variable speed drives (ABB)

Efficient Technologies for Commercial Refrigeration 177 Heat Rejection Control Panel

178 Efficient Technologies for Commercial Refrigeration Variable Setpoint Control

In this method of providing floating head pressure, the condensing temperature setpoint changes with the weather (i.e., the ambient temperature). This type of floating head pressure sets condensing temperature low limit and high limit setpoints that are maintained regardless of the ambient temperature. In other words, the amount the condensing temperature is allowed to “float” is restricted. This can be accomplished using two speed fan motors with fan cycling, or using variable speed drives on the fan motors.

Ambient Temperature Condensing Temperature Setpoint

100 High limit Condensing temperature setpoint 90 Setpoint varies with ambient temperature 80

70

60 Low limit

50 Ambient temperature 40

Variable setpoint control

Efficient Technologies for Commercial Refrigeration 179 Floating Suction Pressure

Just as the overall efficiency of a refrigeration system is improved from reduced head pressure on the “high side” of the refrigeration cycle, increasing the pressure on the refrigerant return or “suction” side of the cycle also improves overall system efficiency.

Floating suction requires that the suction pressure control logic acts to increase the suction pressure before the cooling effect is otherwise reduced, by operation of a liquid solenoid or the setpoint of a suction regulator. For suction groups serving walk-in boxes with evaporator fan speed control, the control automation would need to prioritize fan speed reduction before allowing suction temperature to float. Computer control of temperatures in the display cases and walk-ins is a standard feature.

Low Temperature High Temperature 100 System System Floating Floating Head Head 70

20 Floating Suction

–20 Floating Suction Evaporator / Condensing / Temp Evaporator

180 Efficient Technologies for Commercial Refrigeration Suction pressure is the pressure of the refrigerant as it enters the compressor (through the suction line and manifold) from the evaporator

Increasing the pressure on the refrigerant return or “suction” side of the cycle improves overall system efficiency

Suction pressure is determined by the temperature requirements of the coldest evaporator in the system.

The pressure of refrigerant at the evaporator must be low enough that it can absorb enough heat to provide the necessary amount of cooling for the evaporator.

Floating suction pressure control strategy is an active, automatic means of optimizing suction pressure on a continual basis. The optimum is the pressure at which the compressor unloads.

The cost associated with floating suction pressure primarily consists of labor costs to commission and fine-tune the controls, plus the 15-year present value of maintenance, ongoing fine-tuning, and setpoint verification.

Efficient Technologies for Commercial Refrigeration 181 Usually a system maintains a suction manifold temperature at the worst-case level of any individual load on the header.

For example, the diagram below illustrates a parallel rack system that has four cases with similar conditions. However, two of the cases have a –23 F setpoint when added to a 2 loss (heat gain through the pipe from the fixture to the manifold), the load at the manifold is –25 F.

If worst case is satisfied, then the suction temperature at the manifold can be reset higher, which uses less energy at the compressors.

Variable suction control mitigates to some extent the fact that parallel systems must accommodate worst-case load temperatures.

How Floating Suction Pressure Saves Energy

With floating suction pressure:  System design loads are high enough to meet the highest expected load  The actual load on evaporator coils varies:  Usually it is excess capacity at design saturated evaporating temperature (SET)  The SET can be safely raised at these times  Raising the SET:  Reduces evaporator capacity and the required “lift” of the suction group  Saves energy at the compressor while maintaining proper temperatures

182 Efficient Technologies for Commercial Refrigeration Fixed vs. Floating Suction Pressure

With fixed suction control:  The suction group saturated suction pressure (SST) setpoint is maintained constantly  SST setpoint is always low enough to meet max cooling load:  Peak temperature, humidity, shopper traffic  Peak infrequent walk-in loads

With floating suction pressure:  The SST setpoint adjusts automatically based on actual fixture requirements  The pressure is no lower than necessary to meet the most demanding fixture or walk-in load  This approach requires coordination with other controls such as mechanical or electronic suction regulators

In a floating suction pressure control strategy, the suction group target saturated suction pressure (SST) setpoint is allowed to vary depending on the actual requirements of the attached loads, rather than fixing the SST setpoint low enough to satisfy the highest expected yearly load.

The target setpoint is adjusted so that it is just low enough to satisfy lowest current saturated evaporating temperature (SET) requirement of any attached refrigeration load while still maintaining target fixture temperatures, but not any higher.

The controls are typically bound by low and high setpoints limits. The maximum float value should be established by the system designer, but a minimum value equal to the design SST (that is no negative float) and a positive float range of 4-6°F of saturation pressure equivalent have been used successfully.

Designers can choose which circuit(s) to float. Usually the most demanding load is the most appropriate, but the specifics should be determined based on the system and the operating conditions.

Efficient Technologies for Commercial Refrigeration 183

The graph above shows hourly values for floating suction pressure control over a one week period, expressed in equivalent saturation temperature.

The suction pressure control setpoint is adjusted to meet the temperature setpoint at the most demanding fixture or walk-in.

The difference in SST between the floating suction pressure control and fixed suction pressure control translates into reduced compressor work and thus energy savings for the floating suction control.

184 Efficient Technologies for Commercial Refrigeration Heat Recovery System Design

There are many possible heat recovery design configurations. System design (controls, piping, valves, heat exchangers, etc.) must meet other requirements in the Standards (e.g., floating condensing temperature).

Variables to consider include:  Type of refrigeration system  Type of HVAC system  Store size  Certain configurations can:  Increase refrigerant charge  Result in greater annual refrigerant losses and associated costs

Possible configurations include:  Direct heat recovery  Indirect heat recovery  Water loop heat pump system

Efficient Technologies for Commercial Refrigeration 185

Series-connected direct condensing heat recovery configuration

In this traditional configuration, the heat recovery coil is placed directly within the HVAC unit airstream (generally the unit serving the main sales area), and the discharge refrigerant vapor from the compressors is routed through the recovery coil and then to the outdoor refrigerant condenser when in heating mode.

If two or more refrigeration systems are used for heat recovery, a multi-circuit heat recovery coil could be used.

This configuration is very suitable when the compressor racks are close to the air handling unit that are to be used for heat recovery.  If the distance is too far, an alternative design should be considered  The long piping runs may result in a refrigerant charge increase that exceeds the maximum defined in the Standards, or there may be excessive pressure losses in the piping that could negatively affect compressor energy.

186 Efficient Technologies for Commercial Refrigeration Check Your Understanding

1. When comparing the relative efficiency of a screw compressor to a reciprocating compressor, the efficiency of the screw compressor is what? a. About the same b. Significantly higher c. Significantly lower d. The comparison is irrelevant in refrigeration applications

2. Most of the new refrigerants are blends that might require special handling. What is the series designation for this type of refrigerant? a. 200 series b. 300 series c. 400 series d. 500 series

3. Floating head pressure is a technique that involves adjusting a refrigeration system setpoint in relation to what variable? a. Ambient pressure b. Ambient air temperature c. Suction pressure d. Product temperature

Efficient Technologies for Commercial Refrigeration 187 Energy Management Systems

After you have implemented various energy saving features in a refrigeration system, the next important step is to control it efficiently.

An energy management system (EMS) integrates microprocessor controls for several systems throughout a facility that use energy, including:  Lighting system controls. These include on/off control, reduced lighting control such as non-public occupancy, during hours when it’s dark outside, daylight response, etc.  HVAC system controls, including temperature and humidity control, ventilation and exhaust, etc.  “Machine room” refrigeration system components, including compressor control of floating suction and discharge control, condensers, electronic expansion valves, solenoid valves, etc.  Case control, including lighting, fixture temperature, anti-sweat heaters, defrost control, etc.

Intelligent defrost methods initiate defrost based on system needs using “conditional logic.” These methods use microprocessors and sensors. The benefits include reduced number of defrost cycles, increased system efficiency, and greater product integrity.

An EMS controller also can control other aspects of the entire system such as variable speed control of compressors and condensers, heat recovery, alarms, diagnostics, etc.

Implementing an EMS will reduce energy use and will maintain system efficiency over time.

Microprocessor controllers for suction pressure are standard equipment on parallel racks. Temperature reset and condenser control using TD strategy are optional features.

Other considerations include:  Control strategies need to fit with equipment design.  Technicians need to understand why the system is controlled.  Computer algorithms are ahead of equipment, engineering, and technicians.

188 Efficient Technologies for Commercial Refrigeration

EMS control (Computer Process Controls, Inc.)

Efficient Technologies for Commercial Refrigeration 189

EMS control (Computer Process Controls, Inc.)

190 Efficient Technologies for Commercial Refrigeration

Refrigeration system control and monitoring system (Dixell)

Efficient Technologies for Commercial Refrigeration 191 Demand Response

Demand response (DR) involves taking actions that lead to a reduction in electrical load.

”Load” or “demand” is defined as an end-use device, or the total power requirement of a site. Demand is usually measured in watts, kilowatts (kW = 1,000 W), or megawatts (MW = 1,000 kW).

Demand response programs are dynamic and temporary, and are designed to encourage a reduction in energy use during designated high demand periods when overall electricity use is at its highest, or when power grid integrity may be at risk.

Demand response is used primarily as a resource for short-term immediate conservation by means of electric load shedding in response to pricing or reliability signals.  “Shedding load” and “load curtailment” both refer to the act of turning off or reducing the operating level or number of devices that use electricity.  “Curtailable load” refers to load from equipment or lighting that can be immediately reduced or shut off.

Summer peaking DR situations are the most common. These are caused by concurrent high system demand and economic constraints (higher wholesale prices). Facilities reduce load either manually or using automated technology such as an energy management system (EMS) or enhanced automation.

Peak loads typically occur on hot summer weekdays between 2 p.m. and 6 p.m. On these days, participants are asked to curtail their demand for a certain amount of time.

192 Efficient Technologies for Commercial Refrigeration Characteristics of Demand Response

Demand response has some specific characteristics:  Demand response actions are taken specifically when requested—usually when peak electric demand is approaching peak electric supply.  Involves temporary, uncommon activities by consumers to reduce energy use, and is different from energy efficiency. Demand response is a temporary action and is different from energy efficiency measures, which involve permanent actions.  Retrofitting the lighting system is considered an energy efficiency measure.  Saving energy by shutting off a portion of the lighting on an everyday basis would not qualify as demand response.  Programs are voluntary. Demand response programs are voluntary, and usually open to commercial, industrial, and residential users who have certain minimum demand levels. Non- voluntary participation occurs during a blackout.  Typically pays incentives. As a rule, participants receive payments or credit for each kilowatt of load curtailed or made available for curtailment, depending on the program.

Efficient Technologies for Commercial Refrigeration 193

Grocery Stores and Supermarkets Grocery stores and supermarkets also offer opportunities for demand response.  Reduce lighting levels  Delay electric resistance defrost control  Ornamental features  Delay anti-sweat heaters  Marketing lighting displays  Some limited air conditioning reduction

 Storage rooms  Vending machines  Sales area  Display cases  Bakery area  Loading dock  Butcher area  Front entrance

Super-  Delay electric resistance defrost control markets  Delay anti-sweat door heaters

 Ornamental features  Postpone or minimize electrical usage in butcher area, bakery, deli, and dishwashing

194 Efficient Technologies for Commercial Refrigeration Automated Demand Response (Auto-DR)

The Automated Demand Response (Auto-DR) program lets utility company customers participate in demand response programs by reducing electricity usage during periods of peak demand without manual intervention.

Customers may design and pre-program levels of participation and automatically take part in a demand response event. Auto-DR customers, through third party firms, may purchase and install qualifying Auto-DR equipment.

Through the Technology Incentives (TI) program, Auto-DR participants are reimbursed per kW of reduced load after the measurement and verification of the installed equipment is completed and indicates the necessary demand response load reduction was achieved.

How Does Auto-DR Work?

Simply put, Auto-DR connects the utility company system to facility systems to enable automated (unmanned) load shed for DR response. Auto-DR technology makes it possible for a facility to automatically achieve specified demand reductions (kW and duration) during demand response events.

When an Auto-DR event occurs, a central system sends a signal through the Internet to a device on the customer’s site, which then triggers the Energy Management System to reduce load.

Auto-DR is designed to save money and energy by offering financial incentives in exchange for shifting or reducing energy use during critical energy demand periods.

Customers design and pre-program their own electrical load reduction strategies.

Efficient Technologies for Commercial Refrigeration 195 How Refrigeration Facilities Can Reduce Energy Costs

There are several refrigeration system design features that, when implemented, can offer energy efficiency potential. Facilities that use refrigeration can reduce energy costs by implementing:  High-efficiency compressors and condensers  Dehumidification for better refrigerant performance  Subcooling—the system refrigerant is refrigerated, which provides more cooling capacity for greater system efficiency  Floating condenser head pressure—“floating” (increasing and decreasing) the compressor/condenser head pressure with changing outdoor temperatures improves system efficiency and reduces energy losses. The lower the head pressure, the less the compressor needs to work.  Microprocessor-based control systems

Energy efficiency issues include:  Operating efficiency at peak conditions and full load.  Operating efficiency at “off-design” conditions and partial load (which is almost all of the time).  Operating efficiency criteria:  A system operating at full-load will run efficiently  The main efficiency issues arise at partial load

Better efficiency (kW/ton) can be realized with favorable system conditions, specifically, favorable operating condensing temperatures and evaporating temperatures.

196 Efficient Technologies for Commercial Refrigeration Small Factors in Design Efficiency

Factors that have a smaller overall effect on design efficiency include:  Compressor choice:  Compressor manufacturer  Screw compressors vs. reciprocating compressors Screw and reciprocating compressors have about the same efficiency. More important than the compressing technology used is how they are applied in refrigeration systems.  Refrigerant choice.

Big Factors in Design Efficiency

Factors that have a larger overall effect on design efficiency include:  System selection and features—this includes the selection of parallel vs. conventional systems, standard vs. high-efficiency components (such as motors and condensers), control systems (energy management systems), etc.  Condenser choice (heat rejection)—there are new, more efficient choices available from manufacturers. There are still some inefficient condensers on the market (watch out for the low-efficiency “dogs” out there).  System balance and optimization—this includes a “balanced” choice of compressor and condenser options, and such features as subcooling, floating head pressure, floating suction pressure, variable speed drives on the condenser fan, etc.

Efficient Technologies for Commercial Refrigeration 197 Other features not discussed in detail in these materials that offer energy efficiency benefits include:  Hot-gas defrost—Gas defrost uses heat from the compressor’s discharge gas to defrost the evaporators (remove the coil frost). Hot-gas defrost can be used only in systems with multiple evaporators.  Heat reclaim (heat recovery)—The heat given off by compressors is usually discharged to air or water at the condenser. This heat can be captured and used to heat the store or to provide water heating. In heat reclaim systems, the superheat vapor from the compressor discharge is diverted to a heat-reclaim coil.  Thermal energy storage (TES)—also called “cool storage” or “off-peak air conditioning” systems, TES may be used to provide cooling capacity for air conditioning or for process cooling, and take advantage of the lower energy costs of non-peak hours. Conventional chillers or industrial-grade ice-making machines are used produce cooling capacity which is stored in the form of chilled water or some type of “ice.” The stored energy is then used to supply cooling capacity for air conditioning or process cooling.

Research (by EPRI and others) has found that floating head pressure, hot-gas defrost, and heat reclaim produce the most energy efficiency benefits. Also, by closely matching the display case temperatures to those of the compressors, and by using specialized HVAC systems designed for reducing humidity, energy use is also improved.

The ability to vary the capacity to match system load helps maintain the highest possible system efficiency and can achieve dramatic energy use savings. Demand savings for a parallel system are about 20% of a refrigeration system’s demand.

The table below describes typical energy efficiency measures and typical energy savings.

Typical % Savings for Individual Measures Measure Description Application Base Condition Energy Floating condenser head Larger new systems Fixed head pressure 10-25% pressure control Evaporative condenser Remote condensers Air-cooled 10% (new) Mechanical subcooling Larger systems Conventional 20% Ambient subcooling Larger systems Floating head (no 1-3% subcooling) Liquid suction subcooling All systems Conventional system 5% Hot gas defrost New systems Electric resistance defrost 10-15% Heat reclaim All systems Gas heat 5%

198 Efficient Technologies for Commercial Refrigeration California’s Title 24 Energy Code

The California Code of Regulations (CCR) is the official compilation and publication of the state’s regulations. Properly adopted regulations that have been filed with the Secretary of State have the force of law.

The CCR is compiled into numbered “Titles.” For example, Title 3 addresses food and agriculture regulations, Title 4 addresses business regulations, and Title 24 is the Building Standards Code. (See “Full List of Titles in the California Code of Regulations” below for a full list of the 28 Titles in the CCR as of October 2013.)

The provisions of California Code of Regulations (CCR), Title 24 include requirements for:  Structural, plumbing, electrical and mechanical systems of buildings  Fire and life safety  Energy conservation and green design  Accessibility in and about buildings

Title 24 is organized into separate parts, each addressing a specific area of the regulations.

Title 24, Part 6, contains the regulations that govern building energy efficiency standards for new construction as well as alterations and additions to existing residential and nonresidential building systems.

Efficient Technologies for Commercial Refrigeration 199 The Parts of Title 24: California Building Standards Code Title 24 Part Name Part 1 California Building Standards Administrative Code Part 2 California Building Code (based on the 2009 International Building Code) Vol. 1 and 2 Part 2.5 California Residential Code (based on the 2009 International Residential Code) Part 3 California Electrical Code (based on the 2008 National Electrical Code) Part 4 California Mechanical Code (based on the 2009 Uniform Mechanical Code) Part 5 California Plumbing Code (based on the 2009 Uniform Plumbing Code) Part 6 California Energy Code (also called the Energy Efficiency Standards for Residential and Nonresidential Buildings) Part 7 No longer published in Title 24; see Title 8: Industrial Relations of the CCR Part 8 State Historical Building Code Part 9 California Fire Code (based on the 2009 International Fire Code) Part 10 California Existing Building Code (based the 2009 International Existing Building Code ) Part 11 California Green Building Standards Code (also called the CALGreen Code) Part 12 California Reference Standards Code

Title 24: California Building Code as It Commonly Is Published in Hardcopy

200 Efficient Technologies for Commercial Refrigeration Title 24, Part 6: The Energy Efficiency Standards for Residential and Nonresidential Buildings

Most of the “Parts” of Title 24 are adopted and go into effect at the same time. Title 24, Part 6, historically has been on a different adoption cycle. For example, most of the current Building Standards Code (Title 24) is known as the 2013 code. 2013 is the year those regulations were adopted; they went into effect July 1, 2014.

However, the current Title 24, Part 6, (Building Energy Efficiency Standards) was adopted by the California Energy Commission (CEC) and approved by the CBC in 2013. Therefore, Part 6 is known as the 2013 Standards.

Goals

The Building Energy Efficiency Standards are developed by experts in each field addressed by the Standards who weigh the expense of energy efficiency measures against the energy savings they are expected to provide. Only measures that are considered cost-effective are incorporated into the Standards. The overall goals of the Title 24, Part 6 include:  Provide California with an adequate, reasonably priced, and environmentally sound supply of energy  Respond to Assembly Bill 32, the Global Warming Solutions Act of 2006 and the West Coast Governors' Global Warming Initiative, which call for significant reduction in California’s greenhouse gas emissions  Address the goals of The California Energy Efficiency Strategic Plan and 2007 Integrated Energy Policy Report, which adopt zero net energy goals for new construction in California (See “What is Zero Net Energy?” below for more information.)  Act on the California's Integrated Energy Policy Report, which found that Standards are the most cost-effective way to achieve energy efficiency

Each update of the Standards is designed to achieve greater energy savings than the previous version. According to the Impact Analysis for the 2013 Building Energy Efficiency Standards,1 the 2013 Standards will achieve the following savings on top of the savings from the 2008 Standards:  Electricity:  555 Gigawatt-hours annual savings  148 Megawatts nonresidential demand reduction  Natural Gas:  7.04 Million Therms natural gas annual savings

1 CEC pub number 400-2013-008 (July 2013) ; you can download the full Impact Analysis here: http://www.energy.ca.gov/2013publications/CEC-400-2013-008/CEC-400-2013-008.pdf

Efficient Technologies for Commercial Refrigeration 201 Mandatory Measures and Compliance Methods

In general, the Standards define Mandatory Measures and two approaches to complying with the standards: the Prescriptive Approach and the Performance Approach.  Mandatory Measures are basic requirements must be met — always. They may be exceeded ("better than") — anytime.  The Prescriptive Approach is a relatively simple but inflexible approach for demonstrating compliance with the Standards for most types of buildings. The Prescriptive approach requires all components of a building meet minimum requirements for that component. These requirements vary by the climate zone.  The Performance Approach is a relatively complex but flexible method that uses approved software to calculate the energy budget for a building system and ensures that the proposed energy budget is equal to or better than the energy budget would be if the project used the Prescriptive approach. This allows tradeoffs among measures and most end uses (if included in the building permit); for example, you can use some less-efficient components if they are offset by components that are more efficient than those specified in the Prescriptive approach.  Compliance documentation refers to the forms and related information that must be provided to the enforcement agency (building department) to demonstrate that the project complies with the Standards. Appropriate compliance documentation is required regardless of the approach used to demonstrate compliance.

202 Efficient Technologies for Commercial Refrigeration Full List of Titles in the California Code of Regulations

The following are the Titles composing the CCR as of October 2013. Title 1: General Provisions Title 2: Administration Title 3: Food and Agriculture Title 4: Business Regulations Title 5: Education Title 7: Harbors and Navigation Title 8: Industrial Relations Title 9: Rehabilitative and Developmental Services Title 10: Investment Title 11: Law Title 12: Military and Veterans Affairs Title 13: Motor Vehicles Title 14: Natural Resources Title 15: Crime Prevention and Corrections Title 16: Professional and Vocational Regulations Title 17: Public Health Title 18: Public Revenues Title 19: Public Safety Title 20: Public Utilities and Energy (includes Article 4: Appliance Efficiency Regulations, as well as regulations governing the public utilities and power plants) Title 21: Public Works Title 22: Social Security Title 23: Waters Title 24: Building Standards Code Title 25: Housing and Community Development Title 26: Toxics Title 27: Environmental Protection

Efficient Technologies for Commercial Refrigeration 203 What Is Zero Net Energy?

One key aspect of the California Energy Efficiency Strategic Plan is to achieve “zero net energy” for new construction in California:  All new residential construction in California will be zero net energy by 2020  All new commercial construction in California will be zero net energy by 2030  50% of existing commercial buildings retrofit to ZNE by 2030

Zero net energy (ZNE) is a general term applied to a building with a new energy consumption of zero over a typical year. To cope with fluctuations in demand, zero energy buildings are typically envisioned as connected to the grid, exporting electricity to the grid when there is a surplus, and drawing electricity when not enough electricity is being produced.

Zero Net Energy

 The amount of energy provided by on-site renewable energy sources is equal to the amount of energy used by the building.

 A ZNE building may also consider embodied energy — the quantity of energy required to manufacture and supply to the point of use, the materials utilized for its building.*

* Several green building standards take embodied energy into account. See, for instance, US Green Building Council Leadership in Environmental and Environmental Design (LEED) (http://www.usgbc.org) or UK Code for Sustainable Homes (http://www.planningportal.gov.uk/buildingregulations/greenerbuildings/sustainablehomes/)

Source: California Energy Efficiency Strategic Plan, January 2011, p. 13. (You can download the Strategic Plan at http://www.cpuc.ca.gov/PUC/energy/Energy+Efficiency/eesp/.)

204 Efficient Technologies for Commercial Refrigeration Documents that Detail and Support the Standards The table below notes the primary documents that define and support Title 24, Part 6. (There also are documents that note the calculations and user interface specifications used in the compliance software used to demonstrate compliance using the Performance Approach.)

Title Commonly Description Download Referred to As 2013 Building The Standards (Title The actual http://www.energy.ca.gov/2012publications/CEC-400- Energy Efficiency 24, Part 6) regulations (have 2012-004/CEC-400-2012-004-CMF-REV2.pdf Standards for the force of law) Residential and Nonresidential Buildings 2013 Reference Reference Supporting http://www.energy.ca.gov/2012publications/CEC-400- Appendices of Appendices documentation 2012-005/CEC-400-2012-005-CMF.pdf the 2013 . Joint Appendices that provides Building Energy (JA) definitions, Efficiency calculations, and . Residential Standards for detailed Appendices (RA) Residential and descriptions of Nonresidential . Nonresidential methods called for Buildings Appendices (NA) in the Standards 2013 Compliance Manuals that serve Nonresidential: Compliance Manuals as a reference and http://www.energy.ca.gov/2013publications/CEC-400- Manuals for the . Residential an instructional 2013-002/CEC-400-2013-002-CMF.pdf 2013 Building Compliance guide for the Energy Efficiency Standards — Manual (RCM) Residential: Standards providing . Nonresidential http://www.energy.ca.gov/title24/2013standards/residential_manual.html explanations, Compliance examples, and Manual (NRCM) frequently asked questions and answers that illustrate how the Standards apply to various situations. These manuals can be helpful for anyone that is directly or indirectly involved in the design and construction of energy efficient buildings.

Efficient Technologies for Commercial Refrigeration 205 Title 24 Compliance for Commercial Refrigeration

Title 24 code for supermarket refrigeration systems is Included under the section for covered processes. It applies to retail food stores with 8,000 square feet or more of conditioned area, and that utilize either: refrigerated display cases, or walk-in coolers or freezers connected to remote compressor units or condensing units.

The following summarizes the associated code for commercial refrigeration.  Condenser requirements:  Continuously variable speed, with the speed of all fans serving a common condenser high side controlled in unison  Variable setpoint control logic  Minimum condensing temperature  Specific efficiency requirements  Compressors:  Control systems for floating suction pressure  Liquid subcooling for low-temperature compressor systems  Refrigerated Display Cases. Lighting in refrigerated display cases, and lights on glass doors installed on walk-in coolers and freezers shall be controlled by one of the following:  Automatic time switch controls to turn off lights during nonbusiness hours.  Motion sensor controls  Refrigeration Heat Recovery  Limits to increase in HFC refrigerant charge

206 Efficient Technologies for Commercial Refrigeration SECTION 120.6 – MANDATORY REQUIREMENTS FOR COVERED PROCESSES

(b) Mandatory Requirements for Commercial Refrigeration

Retail food stores with 8,000 square feet or more of conditioned area, and that utilize either: refrigerated display cases, or walk-in coolers or freezers connected to remote compressor units or condensing units, shall meet the requirements of Subsections 1 through 4.

1. Condensers serving refrigeration systems. Fan-powered condensers shall conform to the following requirements:

A. All condenser fans for air-cooled condensers, evaporative-cooled condensers, air or water-cooled fluid coolers or cooling towers shall be continuously variable speed, with the speed of all fans serving a common condenser high side controlled in unison.

B. The refrigeration system condenser controls for systems with air-cooled condensers shall use variable setpoint control logic to reset the condensing temperature setpoint in response to ambient drybulb temperature.

C. The refrigeration system condenser controls for systems with evaporative-cooled condensers shall use variable-setpoint control logic to reset the condensing temperature setpoint in response to ambient wetbulb temperature. EXCEPTION to Section 120.6(b)1B and C: Condensing temperature control strategies approved by the executive director that have been demonstrated to provide equal energy savings.

D. The minimum condensing temperature setpoint shall be less than or equal to 70°F.

E. Fan-powered condensers shall meet the specific efficiency requirements

[ Several exceptions ]

… 2. Compressor Systems. Refrigeration compressor systems and condensing units shall conform to the following requirements.

A. Compressors and multiple-compressor suction groups shall include control systems that use floating suction pressure logic to reset the target saturated suction temperature based on the temperature requirements of the attached refrigeration display cases or walk-ins. EXCEPTION 1 to Section 120.6(b)2A: Single compressor systems that do not have continuously variable capacity capability. EXCEPTION 2 to Section 120.6(b)2A: Suction groups that have a design saturated suction temperature of 30°F or higher, or suction groups that comprise the high stage of a two-stage or cascade system or that primarily serve chillers for secondary cooling fluids.

B. Liquid subcooling shall be provided for all low temperature compressor systems with a design cooling capacity equal or greater than 100,000 Btu/hr with a design saturated suction temperature of -10°F or lower, with the subcooled liquid temperature maintained continuously at 50°F or less at the exit of the subcooler, using compressor economizer port(s) or a separate medium or high temperature suction group operating at a saturated suction temperature of 18°F or higher. EXCEPTION to Section 120.6(b)2B: Low temperature cascade systems that condense into another refrigeration system rather than condensing to ambient temperature. EXCEPTION to Section 120.6(b)2A and 2B: Existing compressor systems that are reused for an addition or alteration.

Efficient Technologies for Commercial Refrigeration 207 3. Refrigerated Display Cases. Lighting in refrigerated display cases, and lights on glass doors installed on walk-in coolers and freezers shall be controlled by one of the following:

A. Automatic time switch controls to turn off lights during nonbusiness hours. Timed overrides for any line-up or walk-in case may only be used to turn the lights on for up to one hour. Manual overrides shall time-out automatically to turn the lights off after one hour.

B. Motion sensor controls on each case that reduce display case lighting power by at least 50 percent within 30 minutes after the area near the case is vacated. EXCEPTION to Section 120.6(b)3: Stores which are normally open for business 140 hours or more per week.

4. Refrigeration Heat Recovery.

A. HVAC systems shall utilize heat recovery from refrigeration system(s) for space heating, using no less than 25 percent of the sum of the design Total Heat of Rejection of all refrigeration systems that have individual Total Heat of Rejection values of 150,000 Btu/h or greater at design conditions. EXCEPTION 1 to Section 120.6(b)4A: Stores located in Climate Zone 15. EXCEPTION 2 to Section 120.6(b)4A: HVAC systems or refrigeration systems that are reused for an addition or alteration.

B. The increase in hydrofluorocarbon refrigerant charge associated with refrigeration heat recovery equipment and piping shall be no greater than 0.35 lbs per 1,000 Btu/h of heat recovery heating capacity.

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Efficient Technologies for Commercial Refrigeration 209

210 Efficient Technologies for Commercial Refrigeration