(HVAC) Controls

Heating, Ventilating and Air Conditioning (HVAC) Controls

Codes and Standards Enhancement (CASE) Study

November 28, 2000

Pacific Gas and Electric Company Patrick Eilert Pacific Gas and Electric Co. P.O. Box 770000, H28E San Francisco, CA 94177 Phone: 530-757-5261 E-mail: [email protected]

This report was prepared by Pacific Gas and Electric Company and funded by California utility customers under the auspices of the California Public Utilities Commission. Neither PG&E nor any of its employees and agents: 1. makes any written or oral warranty, expressed or implied, regarding this report, including but not limited to those concerning merchantability or fitness for a particular purpose; 2. assumes any legal liability or responsibility for the accuracy, completeness, or usefulness of any information, apparatus, product, process, method, or policy contained herein; or

3. represents that use of the report would not infringe any privately owned rights, including, but not limited to, patents, trademarks, or copyrights. Copyright 2000 Pacific Gas and Electric Company. All rights reserved. Reproduction or distribution of the whole or any part of the contents of this document without the express written permission of PG&E is prohibited. Neither PG&E nor any of its employees makes any warranty, express or implied, or assumes any legal liability of responsibility for the accuracy, completeness, or usefulness of any data, information, method, policy, product or process disclosed in this document, or represents that its use will not infringe any privately- owned rights, including but not limited to patents, trademarks or copyrights.

Table of Contents

ACKNOWLEDGMENTS ...... II

INTRODUCTION...... 1

TECHNOLOGY DESCRIPTION...... 1

CURRENT PRACTICE...... 1

ECONOMIZERS...... 1 FAN CONTROLS ...... 2 DIAGNOSTIC SYSTEMS ...... 3 MARKET CHARACTERISTICS ...... 3 EQUIPMENT RELIABILITY ...... 5 ECONOMICS ...... 5

COSTS...... 5 BENEFITS...... 5 AVAILABILITY...... 7 STATEWIDE ANALYSIS ...... 8 KEY STAKEHOLDERS...... 9

IMPLEMENTATION STRATEGIES AND RECOMMENDATIONS ...... 9

APPLIANCE EFFICIENCY REGULATIONS ...... 9 ENERGY EFFICIENCY STANDARDS FOR BUILDINGS ...... 9 VOLUNTARY STANDARDS ...... 10 FUTURE RESEARCH ...... 10 BIBLIOGRAPHY...... 11

Acknowledgments

The New Buildings Institute developed this Codes and Standards Enhancement Study for the Pacific Gas and Electric Company under Contract 4600010614, part of PG&E’s Codes and Standards Program for 1999. Project managers for PG&E included Jennifer Barnes, Patrick Eilert, Gary Fernstrom and Marshall Hunt. Jeffrey A. Johnson, Senior Program Director of the New Buildings Institute, managed this project. Subcontractors on this project were: Eley Associates: Charles Eley Architectural Energy Corporation: Pete Jacobs Dave Roberts Kosol Kiatreugwattana Dan Bertini Don Felts Energy Consulting: Don Felts

The following individuals reviewed and advised the project: Cathy Higgins, New Buildings Institute; Bill Pennington, Michael Martin and Jonathan Leber, California Energy Commission. Produced by: New Buildings Institute, Inc. PO Box 653 White Salmon, WA 98672 E-mail: [email protected] Web: www.newbuildings.org

This study focuses on economizer controls, Introduction including dampers, linkage, actuators, temperature sensors, and electronic and/or This Codes and Standards Enhancement electromechanical components required to (CASE) Study provides information to determine damper position. support updating HVAC Controls External controls include manufacturer- requirements in California’s Energy supplied or third party thermostats that Efficiency Standards for Nonresidential control delivery of heating, cooling and Buildings (Standards). In addition, the study ventilation services. The thermostats may looked at possible changes to the Title 20 also include a time clock for temperature Appliance Efficiency Regulations setback during unoccupied periods and fan (Regulations). operation controls. Depending on the local This CASE study examines the following thermostat setting the fans may operate issues relative to HVAC controls on unitary continuously or operate only when the unit equipment: is supplying heating or cooling (cycle on call). · Economizer controls Diagnostic capability refers to self- · Diagnostic systems monitoring systems installed to detect unit · Thermostats and fan controls operational faults that may or may not influence comfort, but may have a This CASE study for HVAC controls significant influence on energy discusses the: consumption. An example of this is a · technology, diagnostic system designed to detect problems in economizer operation. · current practice, · economics, Current Practice · key stakeholders, and

· implementation options and recommendations for inclusion into Economizers codes. The Standards exempt rooftop units under 75,000 Btu/hr nominal cooling capacity (6.25 ton) from economizers. Thus, most Technology Description units 6 tons and smaller do not utilize economizers. Conversely, most units larger HVAC controls on unitary equipment than 6 tons have outdoor air economizers. include internal control systems supplied with the equipment by the manufacturer and The Standards also require an “integrated” external controls that control the delivery of economizer, which is capable of providing heating, cooling and ventilation services partial cooling, even when mechanical according to occupant requirements. cooling is required to meet the remaining cooling load. Effective operation of an Internal control systems for unitary integrated economizer requires a compressor equipment include outdoor air damper system that provides stable operation at (economizer) controls, refrigerant flow partial cooling output. Units larger than 6 controls, heat pump refrigerant reversing tons generally use multistage compressors to controls, heat pump compressor and strip provide at least two discrete levels of heat controls, compressor staging controls, cooling output. and condenser fan staging controls.

Control strategies used with integrated during fan operation. The quantity of systems include: outdoor air is determined by the minimum outdoor air damper position. The supply of · Fixed temperature. The economizer continuous fresh air during occupied hours shuts off when the outdoor temperature relies on continuous operation of the HVAC exceeds a fixed set point, usually 75°F. unit supply fan. · Differential temperature. The Most simple thermostats used to control economizer shuts off when the outdoor unitary equipment provide an easily temperature exceeds the return air accessible switch on the face of the temperature. thermostat that determines fan operation. · Fixed enthalpy. The economizer shuts When set to the “on” mode, the fan runs off when the outdoor enthalpy exceeds continuously. When set to the “auto” mode, a fixed value. the fan only runs when the space loads are sufficient to require heating or cooling. · Differential enthalpy. The economizer Supply fan operation, and thus ventilation shuts off when the outdoor air enthalpy requirements, rely on the manual daily exceeds the return air enthalpy. setting of the fan on/auto switch to the “on” The current (1998) Standards leave the position. option open as to whether economizers have There is a growing body of evidence to temperature or enthalpy controllers. suggest that proper operation of ventilation California’s dry climate tends to indicate fans does not occur. A review of short-term that enthalpy economizer controllers do not monitored data collected by Architectural affect unitary equipment energy use or Energy Corporation on about 100 packaged enhance energy savings. Proposed changes rooftop units around the country showed to the Standards under the AB 970 about 25% of the units operated in “auto” emergency rulemaking procedure1 will mode, with intermittent fan operation. provide specific guidance on the appropriate Onsite surveyor observations of fan mode control strategy by climate zone. These varied widely over the data sources studied, changes are scheduled to take effect in ranging from less than 1% in auto mode in February 2001. the 1998 Southern California Edison (SCE) Nonresidential New Construction (NRNC) Fan Controls evaluation, to almost 50% in auto mode in The Standards require that all buildings not the 1996 PG&E/SCE NRNC evaluation naturally ventilated with operable windows study. A recent study by Lawrence Berkeley or other openings, be mechanically National Laboratory (LBNL) on duct ventilated. Mechanical ventilation is leakage in small commercial buildings found that nine of the ten buildings studied required to occur at least 55 minutes out of every hour that the building is occupied. operated with intermittent fans. Small commercial buildings typically do not The Standards further require that the have sophisticated energy management ventilation system be turned on at least one systems to control ventilation. Building hour before normal building occupancy in outdoor ventilation air is typically supplied order to purge potential build up of pollutants and outgassing from furniture, carpets, paint, etc. Simple thermostats used 1 Assembly Bill 970, among other things, with unitary equipment are typically not requires the California Energy Commission to sophisticated enough to set the unit to purge update the Standards under an emergency the space one hour before occupancy. rulemaking. The Commission was given 120 Without a more sophisticated controller days, or as soon as was practicably feasible, to (thermostat or energy management system), complete the rulemaking.

Diagnostic Systems

Major unitary equipment manufacturers Supply Air Mixed Air Outside Air Return Air Filter Performance Vapor Comp Economizer IAQ Vent. Air Supply such as Trane, York, Carrier and Lennox Train p p p p š p p offer limited diagnostic and reporting Carrier p p p p š š p p features. These are typically light-emitting Lennox p p p p š p diode (LED) and liquid-crystal display (LCD) indicators located on the control York p p p p š p panel at the unit. For the convenience of the Rheem building operator, they are sometimes Rudd p located on a control panel that controls all Regional p units in the building. Brands The LED or LCD indicators generally report p Indicates that manufacturer offers this feature on filter status, and supply air, outdoor air š Indicates very limited diagnostic features and/or return air temperatures. The outdoor air, supply air and return air temperature Figure 1. Summary of Diagnostic System indicators are readouts only. The filter Capabilities diagnostic indicator lights up when the static pressure across the filter exceeds a preset Market Characteristics limit, indicating that a filter change is in order. Two significant studies, RLW 1999 and Felts et al. 1999, show that rooftop units Economizer diagnostics are limited to one provide the majority of commercial building manufacturer, Carrier, who offers an LED cooling in California. Figure 2 shows the that indicates whether or not the economizer number of buildings in the RLW study is in operation. The system only reports that served by packaged versus built-up (chiller) the economizer is in operation, not whether systems. Approximately 90% of the the operation is appropriate. True buildings in the study were served by diagnostics are left up to the service packaged systems. technician. A summary of diagnostic system features is shown in Figure 1:

Figure 2. Market Penetration of Packaged and Built-up Systems

The term “packaged system” generally packaged rooftop AC, single packaged refers to a class of unitary HVAC rooftop heat pump, split system AC, equipment, including single packaged split system heat pump, or dual fuel heat rooftop air conditioners and heat pumps, pump, without evaporative condenser. split system air conditioners and heat Systems of type “B” include units of type A, pumps, packaged terminal air conditioners with evaporative condenser. (PTAC) and packaged terminal heat pumps (PTHP). The California Non-Residential Systems of type “C” include packaged Baseline Study reported the distribution of terminal AC, packaged terminal heat these system types in NRNC as shown in pump, window/wall AC unit, and Figure 3. window/wall heat pump unit. Systems of Type “D” are water loop heat pumps. The size ranges reported are: Packaged C-Small 1% small (£ 5.4 ton), medium (between 5.4

Packaged A-Extra Packaged D-Small and 11.25 ton), large (between 11.25 Large 1% 2% pand 63.3 ton) and extra large (> 63.3 Packaged A-Large ton). 19% Packaged A-Small 48% Air-cooled single packaged and split system air conditioners and heat pumps are the Packaged A-Medium 29% dominant packaged equipment type.

Figure 3. Market Share of Packaged Unitary Systems by System Type Where: Systems of type “A” include single

30%

25%

20%

15%

10% Estimated NRNC Unitary System Market Share

0% 1 2 3 4 5 6 7 10 12 15 20 25 30 40 50 75 100 Unit size (ton)

Figure 4. Market Penetration of Packaged Unitary AC and Heat Pumps by Cooling Capacity

Figure 4 illustrates the frequency spite of this, very few units actually had a distribution of Type A system sizes. These functioning economizer that took advantage data show that the majority of the systems of this free cooling opportunity. are 5 tons or less, with 5 tons being the most popular unit size. Economics From these data, it is evident that the current economizer requirements, which require Costs economizers on units larger than 6.25 ton, do not address the majority of the HVAC Costs to add economizers to small packaged systems installed in new California rooftop units were estimated in this study. buildings. Based on interviews conducted by AEC with distributors of Carrier, Trane, York and Lennox equipment, economizer options for a Equipment Reliability typical 5-ton unit add about $400–$800 to The 1999 ASHRAE HVAC Applications the unit cost. Additional labor to install and Handbook, Chapter 35, Table 3, lists the test the system adds another two hours to the rooftop unit service life at 15 years. A installation cost. Assuming a midpoint research project by Breuker and Braun estimate of first costs, and a labor rate of (1999), examined the service records for $75 per hour, the total cost of adding an over 6,000 rooftop units. They classified economizer to a five-ton unit is about $750. faults, which caused “no air conditioning” Average maintenance and repair costs over service calls. the 15-year life of the unit is estimated at $250 every 5 years Significant fault categories include: control error, 21%; electrical problems, 20%; refrigerant leak, 12%; condenser failure, Benefits 7%; and air handling failure, 7%. The The benefits of adding economizers to project rates the cost to repair faults by smaller units were investigated through the listing the percent of each category’s repair use of DOE-2 simulations of a simple dollars that goes toward repairing specific prototypical building. The prototype components. In the control system fault building characteristics are summarized category, the repair cost breaks down as below: follows: recalibrate/reset thermostat, 24%; general controls malfunction, 20%; replace · Shape. 1600-ft_ single zone building thermostat, 19%; and compressor control with a square footprint. Glazing area failure, 17%. equal to 25% of the vertical wall area applied to each orientation. Curiously, the study does not list economizer malfunction. Presumably, · Shell characteristics. Building shell economizer malfunction would not trigger a characteristics are set to Title 24 “no air conditioning” service call. The minimum values. project did not examine service lives of the · Occupancy. A typical 8 AM to 5 PM rooftop unit components. office occupancy schedule is used, with A study by Felts et al. (1999), showed that an occupant density and ventilation rate generally in the PG&E service territory, appropriate for office occupancy (7 economizers on unitary equipment either do persons/1000 ft_ and 15 CFM/person). not exist or they do not work. Of 250 · Controls. Control actions specified in packaged rooftop units that were monitored, the Standard are simulated, including a majority of the units had a time during the continuous fan operation during monitoring period when an economizer occupied hours, one-hour building flush could have satisfied all or part of the load. In and night thermostat setback.

The DOE-2 simulations assumed a non- · Fresno: CTZ11, CTZ12, CTZ13 integrated economizer, since most small · Long Beach: CTZ05, CTZ06, CTZ07, systems do not have the ability to modulate CTZ08, CTZ09, CTZ10 cooling output. · Shasta: CTZ01, CTZ16 Energy impacts were evaluated using a preliminary version of the time dependent Figure 5 shows energy cost savings, valuation (TDV) procedure. The TDV expressed as a percent of the total using the procedure assigns a specific value to energy TDV procedure, for non-integrated consumption for each hour of the year. The economizers applied to small systems. 8760 hourly values represent the net present The benefits of improved control of supply value (NPV) of energy costs over a 15-year fan systems were evaluated in terms of the life cycle, using a 3% real discount rate. For impacts of improved control on the effective more information on this procedure, see the ventilation rate. Effective ventilation rate Time Dependent Valuation Summary Report 2 procedures were developed for intermittent done by PG&E. fan and intermittent occupancy based on a For this project, data for five cities were CO2 balance on the space, similar to available, which were mapped to the Sherman et al. See Appendix A for a more California climate zones (CZ) as follows: detailed description of the effective ventilation rate procedure. · Oakland: CTZ02, CTZ03, CTZ04

· China Lake: CTZ14, CTZ15

2 Figure This report 5. Energyand tools necessarySavings tofrom evaluate Non-integrated the Economizers Applied to Small Unitary Systemspreliminary by TDV Climate Procedure Zone can be accessed at http://www.h-m-g.com/tdv/index.htm.

Effective OA comparison

CTZ 15 CTZ 12 15 CTZ 3 OA cfm/person

0 Base Intermittant fan Run

Figure 6. Impacts of Intermittent Fans on Effective Ventilation Rate

Figure 6 shows the impacts of intermittent Optional manufacturer-supplied fan control on effective ventilation rate. programmable thermostats include supply fan on/auto programming with each time Note that the effective ventilation rate goes step. They typically have 24 programmable below the code minimum of 15 CFM/person time steps for each day type, as shown in in all climate zones studied when Figure 7. intermittent fans are used.

Hour 1 2 3 4 5 6 ~ 9 10 11 AM AM AM AM AM AM AM Am AM Set 62 62 62 62 65 65 72 72 72 Availability Point

Economizers are widely available on units Fan Auto Auto Auto Auto Auto On On On On between 3 tons and 6.25 tons of cooling capacity. However, integrated economizers Figure 7. Thermostat Setpoint and Fan not available on units with single-stage Control Logic compressors, which comprise the majority of small units. The major manufacturers offer master and slave programmable thermostats for Programmable thermostats for packaged buildings with multiple units. They also unitary equipment are widely available from offer control panels that provide a central many sources including the unitary programming access point for the equipment manufacturers. The basic thermostats on all units. All programmable programmable thermostat has time of day thermostats have override features that allow and day of week features with a manual the user to set up or back temperatures on/auto fan switch. during nonbusiness hours.

Diagnostic systems capable of detecting monthly utility billing data when the data economizer faults are not available at this were available. time. Trane “Intellipak” units (greater than The NRNC database represents the broad 20 tons) offer a standard “human interface range of construction practices, climate panel” that provides diagnostic readouts and zones and occupant behavior expected in a fault alarm capabilities, but does not address building population as diverse as the NRNC economizers. Carrier also offers built-in market. Each site in the sample has a diagnostic and fault monitoring systems as statistically derived sample weight and part of their product-integrated controls precision, expressing the relative offered as standard features on rooftop units representation of each building in the NRNC greater than 20 tons. These do not address population, thus allowing the results economizer diagnostics in any significant obtained from simulations of each individual way. York “Millennium” rooftop units offer building to be projected to the population. optional diagnostic controls in units from 15 to 50 tons. Larger rooftops (greater than 20 The NRNC database and DOE-2 modeling tons) represent only a small fraction of the engine were programmed to estimate the total rooftop unit market in California. cost effectiveness of expanding the economizer coverage to include all units with three-ton (36,000 Btu/hr) cooling Statewide Analysis capacity and above. The results of the cost The statewide impacts were projected using effectiveness calculations are summarized the California Statewide NRNC database, a below: collection of 990 buildings selected to · Incremental costs. The NPV of the represent the majority of statewide NRNC incremental costs for adding activity. The majority of the data come from economizers, including first cost, around 800 onsite surveys conducted during installation, and maintenance of a 15- impact evaluation studies of the SCE and year life cycle is estimated at $1,500 per PG&E 1994 and 1996 NRNC energy unit. Total annual installations of units efficiency programs. These data were from 3 to 6.25 tons are estimated at supplemented with thirty audits from the 8,700 units per year, for a total cost of impact evaluation of the 1995 San Diego $13 million. Gas and Electric (SDG&E) NRNC program and additional onsite surveys designed to · Energy Savings. The NPV of the supplement the existing data. Participants in statewide savings using the TDV utility energy-efficiency programs are procedure over a 15-year period is $17.8 included, but are weighted according to their million. general representation in the population. · Cost effectiveness. According to the In the audits, information on building life-cycle analysis, the measure is cost physical characteristics such as types of effective, with a savings-to-investment lighting and plug load inventories, types and ratio (SIR) of 1.4. efficiency of HVAC equipment, insulation Life-cycle costs were not evaluated for levels, and glazing properties were improved ventilation fan controls, since this collected. Building occupants were is a primarily an indoor air quality issue. interviewed to determine behavior Life-cycle costs for diagnostic systems characteristics such as occupancy schedules cannot be evaluated at this time, since the and equipment operation. The onsite data systems do not exist. However, the benefits were used to develop DOE-2 building derived from diagnostics systems can be energy simulation models through an calculated, providing an initial estimate of automated modeling process. Building the market value of implementing the simulation models were calibrated to concept.

The economics of promptly detecting and fixing economizer faults are summarized Implementation Strategies below: and Recommendations · Energy Savings. Assuming 10% of economizers fail open, with the Implementation strategies include updates to remaining units failing in the closed the Standards and Regulations. We position (100% overall failure rate), the recommend that implementation be pursued energy savings potential for diagnostic through both options. controllers applied to all packaged unitary systems three tons and larger Appliance Efficiency Regulations was valued at an NPV of $187 million. Breuker and Braun estimate an Require certification of thermostats and additional energy savings of 5– 20% due other fan system controllers under the to implementation of onboard Regulations. Require that the controllers diagnostics for non-economizer related have the capability to meet the ventilation faults, which are not included in this control strategy requirements under the total. Standards, including continuous ventilation during occupied hours, one-hour building · Sales. Total HVAC unit sales were purge prior to occupancy, and night space estimated at 28,900 units. temperature setback with fans off during · Potential Market Value: 15-year NPV unoccupied periods. Develop a labeling of up to $6,500/unit. program to certify thermostats for commercial building applications. Key Stakeholders Economizer reliability should be addressed through the development of economizer The key stakeholders include packaged testing standards by a national standards unitary equipment manufacturers and their organization (Air-conditioning and suppliers, and electronic thermostat control Refrigeration Institute or ASHRAE). The manufacturers. The HVAC equipment standard would establish minimum criteria manufacturer suppliers are an important for failure, sensor location standards, and element, since many manufacturers rely on other criteria to improve the long-term outside vendors such as Cannon Fabrication reliability of economizers. (Canfab) to provide key components such as add-on economizer systems (controls, Energy Efficiency Standards for actuators and damper packages), and Buildings Honeywell and Johnson Controls to supply integrated packaged system controllers. Expand the current economizer requirements to cover all cooling units above 3-ton Other key stakeholders include building (36,000 Btu/hr) cooling capacity. Units owners and contractors, who will need to be under 6.25 tons may comply using a non- convinced of the benefits derived from the integrated economizer. The proposed 2001 added cost of requiring economizers on update under the AB 970 emergency small systems. Improvements in indoor air rulemaking3 provides an efficiency tradeoff quality may help persuade this group of the procedure for economizers applied to value of the proposed change. systems larger than 65,000 Btu/hr cooling

3 For more information on the AB 970 rulemaking, see http://www.energy.ca.gov/ab970_standards.

CASE STUDY PAGE 9 COPYRIGHT 2000 PACIFIC GAS AND ELECTRIC COMPANY output. This procedure should be expanded that promote better indoor air quality and to cover units down to three tons, as shown energy efficiency. in Table 1: Future Research Table 1. Economizer/Efficiency Tradeoff Procedure for Units < 65,000 Btu/hr Providing continuous ventilation through the output4 rooftop unit supply fan may not be the most cost-effective method for introducing Climate Zone Air Conditioner Heat Pump SEER Tradeoff SEER Tradeoff outside air in small commercial buildings. One option to provide ventilation during 1 NA NA periods with no heating or cooling load is to 2 14.4 14.0 use an electronic commutator on small 3 NA NA rooftop unit supply air fan motors in order to 4 14.1 13.7 set back the fan speed to where it is just meeting minimum ventilation requirements 5 NA NA when the unit compressor(s) is not running. 6 NA NA This strategy would require that the unit 7 NA NA have an economizer that would open to 8 14.2 13.8 supply 100% outdoor air when the unit is operating at low fan speed. 9 13.2 12.8 10 12.5 12.1 Another option is to encourage separate, dedicated ventilation systems independent of 11 12.4 12.0 the packaged unitary system for providing 12 12.9 12.5 outdoor air only. These ventilation strategies 13 11.8 11.4 are currently being used in residential codes 14 11.7 11.3 and standards in Washington, Minnesota, Vermont and in Canada. 15 10.7 10.3 16 NA NA Encourage the development of an onboard diagnostic control system designed to detect economizer faults. A project conducted by In addition, the California Energy Pacific Northwest National Lab (PNNL) Commission should adopt economizer (Katipamula et al. 1999) has developed an control strategy requirements to limit the use automated fault detection system for outdoor of enthalpy controls where little or no air ventilation systems and economizers. benefit can be derived. The fault detection system is designed for built-up systems served by an energy Voluntary Standards management system, but is an example of a system that could be incorporated into the A voluntary program to address economizer packaged system internal controller as part and thermostat system performance could be of an onboard diagnostic system. Encourage initiated with the help of the Consortium for industry participation in developing and Energy Efficiency. This program would marketing such a system. promote reliable mechanical linkages, automated diagnostics, and control strategies

4 This table is based on current equipment efficiency levels as prescribed by National Appliance Energy Conservation Act (NAECA).

Delp, Woody, Nance Matson and Mark Bibliography Modera. 1998. Exterior exposed ductwork: delivery, effectiveness and Breuker, Mark and James Braun. 1999. efficiency. ASHRAE Transactions. Evaluating the performance of a fault Case study of the energy and comfort detection and diagnostic system for impact of exposed rooftop ductwork. vapor compression equipment. ASHRAE Transactions. Electric Power Research Institute. 1997. The impact of maintenance on packaged Presents a detailed evaluation of the unitary equipment. performance of statistical, rules-based fault detection and diagnostic techniques Study of the impact of routine for rooftop air conditioning equipment. maintenance on the performance of unitary packaged commercial air Breuker, Mark and James Braun. 1999. conditioning equipment. Common faults and their impacts for rooftop air conditioners. ASHRAE Felts, Don et al. 1999. Roof top unit Transactions. technical potential assessment, working papers. Pacific Gas and Electric Identifies important faults and their Company. performance impacts for rooftop air conditioners. Examines the frequency of Characterization of rooftop packaged occurrence and the cost of service for equipment in northern California different faults. resulting from inspections, monitoring and analyses carried out on over 250 Cummings, James and Charles Withers, Jr. units in widely varying climates. 1998. Building cavities used as ducts: air leakage characteristics and impacts Felts, Don et al. 2000. Roof top unit in light commercial buildings. ASHRAE economizer feasibility study, working Transactions. papers. Pacific Gas and Electric Company. Summarizes field testing in 70 small commercial buildings in central Florida. Review of the feasibility of installing, Identified 33 out of the 70 buildings repairing or replacing rooftop HVAC using building cavities as air distribution unit economizer systems. Follow-up to systems. Examines the energy, the "Roof Top Unit Technical Potential infiltration and relative humidity Assessment" (1999) described above. impacts that result from using building Felts, Don and Patrick Bailey. 2000. The cavities as air distribution systems. state of affairs, package cooling Delp, Woody, Nance Matson and Eric equipment in California. ACEEE Tschudy. 1998. Field investigation of Summer Study Program. duct system performance in California Formal publication of the findings of the light commercial buildings. ASHRAE 1999 "Technical Potential Assessment" Transactions. (see above). Results of a study of 15 systems in eight Honeywell Inc. 1998. Carbon dioxide different buildings located in Northern HVAC basics. California. All of these buildings had the air distribution located in the cavity Honeywell informational document that between the suspended ceiling and the explains the CO2 and IAQ issues in roof deck.. In 50% of these buildings, buildings. the cavity was functionally outside both Honeywell Inc. 1997. A computer study of the building’s air and thermal barriers. the energy savings from using various

economizer changeover strategies in a Lunneberg, Tom. 1999. When good retail store. economizers go bad. Boulder, CO: E Source. Report represents an energy analysis of various economizer control strategies RLW Analytics et al. 1999. California non- including differential enthalpy and residential new construction baseline differential temperature controllers. study. California Board for Energy Examines the benefits and deficiencies Efficiency. of economizer control strategies in Conducted by RLW in association with several different climate types across the Architectural Energy Corporation and the United States. Heschong Mahone Group. Developed from Katipamula, S., R. Pratt, D. Chassin, Z. a database of over 800 onsite surveys Taylor, K. Gowri, and M. Brambley. compiled during evaluations of NRNC DSM 1999. Automated fault detection and programs operated by PG&E, SCE and diagnostics for outdoor-air ventilation SDG&E. Provides statewide coverage of the systems and economizers: methodology new construction marketplace. and results from field testing. ASHRAE Wacker, P.C. Economizer savings study. Transactions 105(1). ASHRAE Transactions. Describes an online economizer and Study of indoor comfort conditions ventilation diagnostic system designed resulting from different economizer to be used with a building automation control strategies including differential system. Describes field tests of the enthalpy and differential temperature system on large built-up air handlers in controllers. two buildings.

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