APPLICATION FOR ADOPTION OF VARIABLE REFRIGERANT FLOW SYSTEMS UNDER THE TITLE 24-2008 NONRESIDENTIAL ACM PROCEDURES

Prepared for:

Daikin AC (Americas), Inc. Mitsubishi Electric, Inc Sanyo North America LG Commercial Air ConditioningPrepared by:

EnergySoft, LLC

Submitted to:

California Energy Commission

PurposeUnder section 10-109(b)4 Exceptional Methods the Building Energy Efficiency Standards (Standards) allow for the introduction of new compliance approaches which cannot be properly accounted for in the current adopted regulation or modeling assumptions. Applications under the exceptional method are called compliance options. The following document is an application for a compliance option that would allow consideration of variable refrigerant flow (VRF) system under the Standards for nonresidential buildings. This application was submitted by EnergySoft on behalf of a number of the manufacturers of VRF systems. Staff has reviewed the document and while the general position of staff is supportive a number of concerns still need to be resolved. Therefore, before a final position can be taken which would hopefully lead to a recommendation to the Commission for approval of this compliance option, staff has held a public meeting to vet out all possible concerns.

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Acknowledgements

The work presented in this document is the culmination of a significant amount of research and development work performed by several of the manufacturers of Variable Refrigerant Flow systems. The authors would like to thank the staff and engineers at Mitsubishi Electric, Inc. including Paul Doppel, Dermot McMorrow, Nicholas Conklin and Meredith Emmerich for their guidance in the initial development of the VRF modeling concept. In addition, development of Mitsubishi specific curve data is credited to Tani Hidekazu. Kenji Obata and Lee Smith with Daikin AC contributed guidance on the Daikin modeling, with technical support provided by Shin Miyazu. Malcolm Perssaud with Sanyo Commercial Solutions provided necessary information to allow modeling of their systems, and information included on the LG systems came from Brian Bogden. Many of the sales team members for the manufacturers contributed to the testing and validation of the work here including Ruben Willmarth, Jim Benville, Sherwin Khayatian and Jon Marshall along with many others. In addition, Tianzhen Hong is to be credited with development of the fundamental equations that are used for the VRF modeling in DOE-2 presented here, as well as the compilation of the manufacturer specific curve coefficients.

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Purpose......................................................................................................................................... i Acknowledgements .................................................................................................................... ii Table of Figures......................................................................................................................... iv Executive Summary ................................................................................................................... 1 Description of VRF Systems ..................................................................................................... 3 Eligibility Criteria ...................................................................................................................... 6 Acceptance Requirements ......................................................................................................... 7 Modeling Procedures ................................................................................................................. 9 Proposed Nonresidential ACM Amendments ....................................................................... 20 Compliance Forms ................................................................................................................... 23 Appendix A The VRF DOE-2 Function .............................................................................. 29Appendix B Daikin Sensitivity -Analysis ...................................................................................... 65 Appendix C Daikin VRV Outdoor Unit RXYMQ48MVJU Performance Data ......................... 67 Appendix D Daikin VRV Outdoor Unit REYQ96MTJU Performance Data ............................. 73 Appendix E Daikin Air-Cooled VRV Generic Performance Curve Data.................................. 79 Appendix F Daikin Indoor Unit Guide Specification .................................................................. 81 Appendix G Daikin VRV Outdoor Unit REYQ96MTJU Guide Specification .......................... 99 Appendix H Daikin VRV Outdoor Unit RXYMQ48MVJU Guide Specification.................... 106 Appendix I Daikin Testing by Intertek ........................................................................................ 110 Appendix J Daikin Case Studies ................................................................................................... 119 Appendix K Daikin Correlation Testing ...................................................................................... 123 Appendix L Mitsubishi Sensitivity Analysis............................................................................... 125 Appendix M Mitsubishi CITY MULTI VRFZ Performance Curve Data ................................ 127 Appendix N Mitsubishi CITY MULTI VRFZ R410A Specifications ........................................ 134 Appendix O Mitsubishi CITY MULTI Indoor Units .................................................................. 140 Appendix P Mitsubishi CITY MULTI Controls .......................................................................... 142 Appendix Q Mitsubishi CITY MULTI Indoor Unit Guide Specification ................................ 144 Appendix R Mitsubishi CITY MULTI PURY-P96 Outdoor Unit Specifications .................... 210 ii

Appendix S Correlation Testing of Mitsubishi CITY MULTI VRFZ Systems ........................ 212 Appendix T Performance Certificate of Compliance for the CITY MULTI VRFZ Systems . 224 Appendix U Performance Certificate of Compliance for the PURY-P96 VRFZ Systems ..... 229 Appendix V Sanyo Sensitivity Analysis ...................................................................................... 232 Appendix W LG Sensitivity Analysis .......................................................................................... 240 Appendix X LG MULTI V Performance Curve Data ................................................................. 242

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Table of FiguresFigure 1 Example Daikin Heat Recovery VRV System Components .............................................. 1 Figure 2 Example Mitsubishi VRFZ System Components ................................................................ 2 Figure 3 - The Capacity Control of a typical VRF System .................................................................... 4 Figure 4 Forms - MECH-2-C............................................................................................................... 25 Figure 5 Forms - MECH-5-C............................................................................................................... 26

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Executive SummaryVariable Refrigerant Flow systems are energy efficient air-conditioning systems that offer savings of electricity and TDV energy as well as reduction of peak electricity demand. However, the 2008 California Building Energy Efficiency Standards (Title 24) do not provide compliance credits for VRF systems, because modeling procedures do not exist in the nonresidential ACM manuals. This application, pursuant to 10-109 of Title 24-2008, recommends modeling procedures to offer credit for VRF systems for nonresidential buildings. The VRF system is a R410A refrigerant-loop heat pump system which works like the conventional water-loop heat pump (WLHP) system, except the VRF system uses an outdoor unit to remove or add heat to the refrigerant loop, while the WLHP system uses a cooling tower to remove heat and a boiler to add heat to the water loop. A heat recovery VRF system can serve multiple zones with some zones demanding cooling while others demand heating. A VRF system has an air-cooled outdoor unit, multiple indoor units, the refrigerant piping loop, one or more optional distribution units, and corresponding system and zone controllers. Figure 1 and Figure 2 show components of a heat recovery VRF system.

Figure 1 Example Daikin Heat Recovery VRV System Components

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The VRF system uses inverter technology by varying the speed of the compressor in the outdoor unit to meet the changing load requirements of each indoor unit. The heat recovery VRF system recycles the energy in other zones to provide comfort only to the zones calling for cooling or heating. The VRF system is energy efficient, quiet in operation, and saves duct work space. This application is organized in the following sections: 1. Executive Summary describes the scope of the application and how VRF system works as well as its benefits. 2. Eligibility Criteria describes VRF system design requirement for compliance credit for nonresidential HVAC systems. 3. Acceptance Requirements describes acceptance requirements for VRF systems. 4. Modeling Procedures describes how VRF systems would be modeled for nonresidential HVAC systems. 5. Proposed Nonresidential ACM Amendments describes needed modifications and additions to the nonresidential ACM manual. 6. Compliance Forms shows reporting and enforcement of VRF systems 7. Appendices provide additional materials for reference as well as the inclusion of Curve Coefficient Data used in the DOE-2 modeling for the various product lines.

Figure 2 Example Mitsubishi VRFZ System Components

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Description of VRF SystemsVariable Refrigerant Flow (VRF) systems are still relatively new to the U.S. market, but have been used in Asia and Europe for more than 20 years. The U.S. has the most comprehensive requirements when compared to other markets worldwide, so there are several issues with testing VRF systems. The first issue is the relatively new testing standard 1230, which is recently released by the Air-conditioning Heating and Refrigeration Institute (AHRI). The second issue is in regards to the set-up, data collection, and control of these complex systems. The systems can be tested with up to five indoor units; in many cases, there may not be enough test room space for the units and all testing apparatus to adequately collect the airflow data. Also, because VRF systems are more complex than standard rooftop or split-system units, with integrated controls and multiple indoor units, the testing time is greater and the cost of set-up and testing becomes very expensive very quickly. Most VRF manufacturers have requested and subsequently received waivers from the Department of Energy (DOE) to be able to sell their systems. The waivers were requested because the older testing standards (ARI Standards 210/240 and 340/360) did not provide adequate information for testing multi-split systems that can have up to 50 indoor units; each outdoor unit can also have thousands of indoor unit combinations. Since the initial waivers, AHRI members have worked with DOE to develop an acceptable testing method, which had been used for the two Mitsubishi systems tested for this report; AHRI has released the AHRI Standard 1230 to test VRF systems. We believe these test results show there is still need for improving testing techniques and capabilities to properly reflect the energy savings potential of VRF systems. The VRF system is a R410A refrigerant-loop heat pump system which works like the conventional water-loop heat pump (WLHP) system, except the VRF system uses an outdoor unit to remove or add heat to the refrigerant loop, while the WLHP system uses cooling towers to remove heat and boilers to add heat to the water loop. A VRF system may have multiple compressors, typically one constant speed and one variable speed with inverter technology. The variable speed compressor system will have multiple capacity control steps which allow the amount of refrigerant flowing in the system to vary depending upon the fluctuating needs of zone loads. This delivers maximum efficiency during partial load conditions and provides precise temperature control in all zones. Each indoor unit incorporates an electronic expansion valve that continually controls the flow rate of refrigerant. In this way, the VRF system maintains a nearly constant room temperature without the typical temperature fluctuations that occur with a conventional ON/OFF control system. By using multiple compressors to regulate capacity, switching losses or power surges are minimized. The heat recovery function is achieved by diverting exhaust heat from indoor units in cooling mode to areas requiring heating and vice versa. The VRF system keeps running cost at an absolute minimum by controlling each zone individually and shutting down completely in unoccupied areas if required. There are two types of VRF systems: the Heat Recovery type which allows for simultaneous zones cooling and heating, and the Heat Pump type which allows for either zones cooling or zones heating operation. A VRF system has an air-cooled outdoor unit, multiple indoor units, the refrigerant piping loop, one or more distribution units (Heat Recovery models only), and corresponding system and zone controllers. An indoor unit needs to connect to a distribution unit if its operation mode needs to be switched automatically from cooling to heating or vice versa independent of the operational mode of the condensing unit. The heat recovery VRF is a three-pipe loop with two pipes connecting each indoor unit to the loop (allows cooling only) or to a Distribution unit (allows either cooling or heating 3

with automatic switching) and three pipes connecting all Distribution units to the outdoor unit. The heat pump VRF is a two-pipe loop with indoor units directly connected to the loop; no Distribution unit is necessary. Figure 1 and 2 show components of a heat recovery series and a heat pump series VRF system. Figure 3 shows capacity control of a VRF system.

Figure 3 - The Capacity Control of a typical VRF System A VRF outdoor unit can connect multiple indoor units with a total capacity of typically 130% - 150% of the outdoor units rated capacity, although some manufacturers do allow higher ratios. VRF systems have been installed in buildings throughout Asia, Europe, and other regions for many years with great success and customer satisfaction. Specifically, VRF systems have the following benefits: Energy efficient. The outdoor unit uses a variable speed compressor system to provide highly responsive cooling and heating performance. By responding to indoor and outdoor temperature fluctuations by monitoring system suction pressure, the system varies power consumption by adjusting the compressor speed to optimize energy usage. The variable capacity indoor units are controlled by electronic expansion valves. This feature allows operation only at the levels required to maintain a consistently comfortable indoor environment without wasting energy. Heat pump operation also offers high heating capacity and efficiency and is more efficient under part load conditions. The nominal cooling efficiency EER can be above 12.0, while the heating COP can exceed 3.5, however, the efficiency values are significantly higher at part load conditions. Flexible indoor layout and design. Each individual zone can have its own indoor unit or a group of indoor units that precisely control the indoor temperature. Multiple styles of indoor units can meet requirements of indoor unit layout and design.

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Zoning comfort control. Zones are actively cooled in one zone while heating another (heat recovery). Set up zones to maximize simultaneous operation: interior/exterior, eastern exposure/western exposure. Each zone gets the cooling or heating that is needed at any time. Simultaneous cooling and heating over three-pipes provides air conditioning and control flexibility to each and every zone. Zoning comfort can also be achieved with the Heat Pump VRF system. Quiet operation. VRF is designed for the quietest possible operation both indoor and outdoor. Outdoor units are as quiet as 58 dB(A) and indoor units as low as 28 dB(A), which makes VRF systems a huge advantage especially for classrooms, schools, universities, hospitals, healthcare facilities, and libraries, where quiet conversations are paramount.

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Eligibility CriteriaVRF systems are energy efficient and eligible for Title 24 compliance credits. The following sections describe the requirements for obtaining the nonresidential credit for VRF systems. New or existing nonresidential buildings can obtain compliance credits for the VRF systems for space cooling, space heating, and fan if the following eligibility criteria are met: 1. Eligible systems shall: Be R410A based refrigerant-loop heat pump systems with multiple direct expansion indoor units and an outdoor unit attached to the loop. Have an air-cooled outdoor unit. Have a variable speed compressor in the outdoor unit to vary the refrigerant flow to meet the changing zone loads. The Heat Recovery VRF outdoor unit can automatically switch operation between cooling mode and heating mode using the "auto" changeover mode. This mode helps move the existing "energy" in a building to the areas it can best be utilized /or is needed, and as such perform heat recovery operation. For the VRF Heat Pump system, users can manually switch the operation mode from cooling to heating and vice versa. Have no supplemental cooling or heating equipment attached to the loop. Have no storage tank. Have each indoor unit operation controlled by a zone controller and/or a system controller. Have a cooling connection ratio (total of indoor unit capacity / outdoor unit capacity) between 50% and 130%. Be installed and tested according to manufacturer installation and operation manuals.

2. Performance data for indoor and outdoor units shall be based upon testing temperature conditions defined in AHRI Standard 1230 for multi-split equipment, which is based on ISO 15042, ARI 210/240, and ARI 340/360 standards. 3. Building types are either nonresidential or high-rise residential.

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Acceptance RequirementsThe following amendments are proposed to the Appendix NJ of the 2008 Nonresidential ACM Manual. VRF Acceptance These acceptance requirements apply only to VRF systems, and are in addition to those for other systems or equipment such as economizers, packaged equipment, etc. Construction Inspection Prior to performance testing, verify and document the following: 1. The air-cooled outdoor unit is installed. 2. For a single VRF system, the actual piping length and total equivalent piping length to the most distant indoor unit is no greater than manufacturers recommendations. The system total piping length is no greater than recommended. Total piping equivalent length = (actual piping length from the outdoor unit to the farthest indoor unit) + equivalent piping length of branches on the piping. 3. The maximum level difference between the outdoor unit and indoor units is no greater than manufacturers recommendations. 4. The VRF system components are installed correctly per manufacturers installation manual, including correct refrigerant (R410A) charge and piping configurations. 5. The correct outdoor and indoor model numbers are installed (as indicated in compliance documents with rated cooling and heating capacities and power consumption of indoor and outdoor units). 6. All refrigerant lines are insulated per the requirements of Title 24 Part 6 Section 118 Equipment Testing For Heat Recovery VRF Systems: 1. Force the controls to indicate all zones demand for cooling. Make sure that all indoor units operate in cooling mode, and the outdoor unit also operates in cooling mode. 2. Force the controls to indicate all zones demand for heating. Make sure that all indoor units operate in heating mode, and the outdoor unit also operates in heating mode. 3. Force the controls to indicate some zones demand for cooling while others demand for heating. Make sure that indoor units demanding for cooling run in cooling mode, while indoor units demanding for heating run in heating mode. The outdoor unit runs in cooling mode if the total cooling demand is greater than the total heating demand of indoor units. 4. Force the controls to indicate some zones demand no cooling or heating while other zones demand cooling or heating. Make sure those indoor units with no demand for cooling or heating do not operate while others do and the outdoor unit also operates. For Heat Pump VRF Systems: 1. Force the controls to indicate dominant cooling demand by zones. Make sure that: 7

Indoor units operate in cooling mode for zones demanding cooling Indoor units do not operate for zones demanding heating Outdoor unit operates in cooling mode

2. Force the controls to indicate dominant heating demand by zones. Make sure that: Indoor units operate in heating mode for zones demanding heating Indoor units do not operate for zones demanding cooling Outdoor unit operates in heating mode

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Modeling ProceduresDOE-2 cannot model the performance of a VRF system; therefore a VRF system function has been developed for DOE-2 to calculate the cooling, heating, and fan energy use of a VRF system. The VRF function takes inputs of the VRF system performance data, hourly indoor and outdoor air temperatures, and hourly zone cooling and heating loads to calculate the hourly outdoor unit power consumption and indoor fan power consumption. The VRF function can be directly called by DOE2.1E to facilitate the simulation of VRF systems. To model a VRF system in DOE-2.1E, the system type is set to HP which is a DOE-2 code word representing the hydronic heat pump system. The VRF function is an after system function which is called after the HP system routine completes an hourly calculation. It basically uses the dummy HP system type and overwrites the way DOE-2 calculates the cooling, heating, and fan energy use for the HP system. The VRF function is called by each VRF system. The VRF function does not change any other energy use in zones, for example, lighting, plug-loads, and any process loads. For the heat recovery VRF system, the VRF function calculates the hourly cooling and heating electricity use of the system according to the zone loads and VRF system performance data. For the heat pump VRF system operates in cooling mode, the VRF function calculates the hourly cooling electricity use of the system according to zone cooling loads and VRF system performance data, but the hourly heating energy is calculated based on zone heating loads. In addition, a user input auxiliary heating system may be specified for colder climates. Should this not be specified, the modeling procedures will automatically define a default electric resistance backup heating system to ensure all loads are met. This methodology is similar to the way a conventional heat pump is handled by the ACM procedures. The same methodology is applied to the cooling system. Should the cooling system be undersized or have unmet load hours, the equations will automatically assign a default minimum efficiency cooling system (13 SEER) to handle unmet loads and ensure all hours of conditioning are reported. This section details the calculation algorithm for a VRF system. The code of the VRF DOE-2 function is listed in Appendix A VRF DOE-2 Function. Appendix A The VRF DOE-2 Function Determination of Operation Mode for a Heat Pump VRF System For a heat pump VRF system, when it is on, it can operate either in cooling mode or heating mode. For a given hour when the VRF system is on, get the hourly total zone cooling loads QCZ, and hourly total zone heating loads QHZ. If QCZ QHZ, then the VRF system operates in cooling mode, otherwise in heating mode. Heat Pump VRF Systems Operate in Cooling Mode Calculation of hourly VRF cooling electricity use Piping correction on outdoor unit cooling capacity PFc_c = f1 + f2*PEL + f3*PEL + f4*LD + f5*CR + f6*CR + f7*PEL*CR Where PFc_c 50F b1 = -1.3372 b2 = 0.022688 $ constant $ ZWB $ Cooling curves split at 50F

b3 = 1.6503E-4 $ ZWB**2 b4 = 7.8004E-3 $ ODB b5 = -2.9177E-5 $ ODB**2 b6 = -6.3973E-5 $ ZWB * ODB $ ODB50F c1 = -6.32 c2 = 0.198 c3 = -1.33E-3 c4 = 0.0 c5 = 0.0 c6 = 0.0 $ ODB