CHAPTER 5. ENGINEERING ANALYSIS

TABLE OF CONTENTS

5.1 INTRODUCTION ........................................................................................................... 5-1 5.2 EQUIPMENT CLASSES AN ALYZED

................................ .......................................... 5-1 5.3 ENERGY EFFICIENCY ME TRIC ................................................................................. 5-2 5.3.1 Cooling Efficiency Metric ................................................................................... 5-2 5.3.2 Heating Efficiency Metric .................................................................................... 5-5 5.4 EFFICIENCY LEVELS

................................ ................................ ................................... 5-5 5.4.1 Baseline Units ...................................................................................................... 5-5 5.4.2 Incremental Efficiency Levels ............................................................................. 5-7 5.5 METHODOLOGY OVERVIEW .................................................................................. 5-12 5.5.1 Manufacturer Interviews .................................................................................... 5-13 5.5.2 Equipment Teardown ......................................................................................... 5-13 5.5.2.1 Selection of Units ..................................................................................... 5-13 5.5.2.2 Generation of Bill of Materials ................................................................ 5-14 5.5.2.3 Cost Structure of the Spreadsheet Models ............................................... 5-14 5.5.3 Shipping Costs ................................................................................................... 5-15 5.5.4 Equipment Testing ............................................................................................. 5-16 5.6 ANALYSIS AND RESULTS ........................................................................................ 5-16 5.6.1 Manufacturer Interviews .................................................................................... 5-16 5.6.2 Equipment Testing ............................................................................................. 5-17 5.6.3 Equipment Teardown ......................................................................................... 5-20 5.6.4 Energy Modeling ............................................................................................... 5-28 5.6.4.1 Heat Exchanger Model ............................................................................. 5-29 5.6.4.2 Compressor Model ................................................................................... 5-32 5.6.4.3 Expansion Model ...................................................................................... 5-33 5.6.4.4 Fan Model ................................................................................................ 5-33 5.6.4.5 Refrigeration Cycle Model ....................................................................... 5-34 5.6.5 Design Option Analysis ..................................................................................... 5-34 5.6.5.1 7.5-ton Models ......................................................................................... 5-35 5.6.5.2 15-ton Models .......................................................................................... 5-38 5.6.5.3 30-ton Models .......................................................................................... 5-41 5.6.5.4 Design Option Summary .......................................................................... 5-45 5.6.6 Cost- Efficiency Results ..................................................................................... 5-48 REFERENCES .......................................................................................................................... 5-50

LIST OF TABLES

Table 5.2.1 Proposed Equipment Classes ......................................................................... 5-2 Table 5.4.1 Baseline Efficiency Levels ............................................................................ 5-6 Table 5.4.2 Incremental Efficiency Levels ..................................................................... 5-12

5-iTable 5.5.1 Major Manufacturing Processes .................................................................. 5-15 Table 5.6.1 Small Air -Cooled CUAC and CUHP Test Units ......................................... 5-18 Table 5.6.2 Large and Very Large Air -Cooled CUAC and CUHP Test Units ............... 5-19 Table 5.6.3 Test Results of Selected Small, Large and Very Large CUAC and CUHP units .................................................................................................. 5-20 Table 5.6.4 Heat Transfer and Pressure Drop Correlations ............................................ 5-32 Table 5.6.5 Design Options for 7.5- Ton CUAC Units ................................................... 5-37 Table 5.6.6 Design Option for 15- Ton CUAC Units ...................................................... 5-40 Table 5.6.7 Design Options for 30- Ton CUAC Units .................................................... 5-44 Table 5.6.8 Design Option Summary for Different Efficiency Levels ........................... 5-46 Table 5.6.9 Small Air -Cooled CUAC and CUHP Cost-Efficiency Relationships ......... 5-49 Table 5.6.10 Large Air -Cooled CUAC and CU HP Cost -Efficiency Relationships ......... 5-49 Table 5.6.11 Very Large Air -Cooled CUAC and CUHP Cost- Efficiency Relationships ................................................................................................ 5-49

LIST OF FIGURES

Figure 5.4.1 Relationship between EER and COP for Heat Pump, ≥65,000 Btu/h and <135,000 Btu/h Cooling Capacity, Electric Heat/No Heating Equipment Class ............................................................................................ 5-8 Figure 5.4.2 Relationship between EER and COP for Heat Pump, ≥135,000 Btu/h and <240,000 Btu/h Cooling Capacity, Electric Heat/ No Heating Equipment Class ............................................................................................ 5-9 Figure 5.4.3 Relationship between EER and COP for Heat Pump, ≥240,000 Btu/h and <760,000 Btu/h Cool ing Capacity, Electric Heat/No Heating Equipment Class ............................................................................................ 5-9 Figure 5.4.4 Relationship between IEER and COP for Heat Pump, ≥65,000 Btu/h and <135,000 Btu/h Cooling Capacity, Electric Heat/No Heating Equipment Class .......................................................................................... 5-10 Figure 5.4.5 Relationship between EER and COP for Heat Pump, ≥135,000 Btu/h and <240,000 Btu/h Cooling Capacity, Electric Heat/No Heating Equipment Class .......................................................................................... 5-10 Figure 5.4.6 Relationship between EER and COP for Heat Pump, ≥240,000 Btu/h and <760,000 Btu/h Cooling Capacity, Electric Heat/No Heating Equipment Class .......................................................................................... 5-11 Figure 5.5.1 Manufacturing Cost Assessment Stages ...................................................... 5-15 Figure 5.6.1 Baseline 7.5 -Ton Air-Cooled CUAC Full Production Cost Distribution .... 5-21 Figure 5.6.2 Baseline 7.5 -Ton Air- Cooled CUAC Materials Cost Distribution .............. 5-21 Figure 5.6.3 Baseline 15 -Ton Air-Cooled CUAC Full Production Cost Distribution ..... 5-22 Figure 5.6.4 Baseline 15 -Ton Air- Cooled CUAC Materials Cost Distribution ............... 5-22 Figure 5.6.5 Baseline 30 -Ton Air -Cooled CUAC Full Production Cost Distribution ..... 5-23 Figure 5.6.6 Baseline 30 -Ton Air- Cooled CUAC Materials Cost Distribution ............... 5-23 Figure 5.6.7 7.5-ton Indoor Coil Face Area * Number of Tube Rows versus IEER ....... 5-24 Figure 5.6.8 7.5-ton Indoor Coil Face Area * Number of Tube Rows versus IEER ....... 5-25 Figure 5.6.9 15-ton Indoor Coil Face Area * Number of Tube Rows versus IEER ........ 5-25

5- iiFigure 5.6.10 15-ton Outdoor Coil Face Area * Number of Tube Rows versus IEER ...... 5-26 Figure 5.6.11 30-ton Indoor Coil Face Area * Number of Tube Rows versus IEER ........ 5-26 Figure 5.6.12 30-ton Indoor Coil Face Area * Number of Tube Row s versus IEER ........ 5-27 Figure 5.6.13 Manufacturing Cost for ~7.5- ton CUAC with Electric Resistance Heating or No Heating ................................................................................. 5-27 Figure 5.6.14 Manufacturing Cost for ~15- ton CUAC with Electric Resistance Heating or No Heating ................................................................................. 5-28 Figure 5.6.15 Manufacturing Cost for ~30- ton CUAC with Electric Resistance Heating or No Heating ................................................................................. 5-28 Figure 5.6.16 User Interface of CoilDesigner .................................................................... 5-30 Figure 5.6.17 Schematic of a Refrigeration Cycle Using a Dual Compressor Configuration ............................................................................................... 5-34 Figure 5.6.18 Model Validation for 7.5- Ton CUAC Units After Applying IEER Weighting Factors ........................................................................................ 5-35 Figure 5.6.19 Model Validation for 15- Ton CUAC Units After Applying IEER Weighting Factors ........................................................................................ 5-38 Figure 5.6.20 Model Validation for 30-Ton CUAC Units with Tube-Fin Condensers After Applying IEER Weighting Factors .................................................... 5-41 Figure 5.6.21 Model Validation for 30-Ton CUAC Units with Microchannel Condensers After Applying IEER Weighting Factors ................................. 5-42 Figure 5.6.22 7.5-Ton EERs at Different Load Conditions for Five Efficiency Levels .... 5-45 Figure 5.6.23 15-Ton EERs at Different Load Conditions for Five Efficiency Levels ..... 5-47 Figure 5.6.24 30-Ton EERs at Different Load Conditions for Five Efficiency Levels ..... 5-47 Figure 5.6.25 Indoor Coil Face Area * Tube Row Number ............................................... 5-48 Figure 5.6.26 Outdoor Coil Face Area * Tube Row Number ............................................ 5-48

5- iiiCHAPTER 5. ENGINEERING ANALYSIS

5.1 INTRODUCTION
After conducting the screening analysis, the U.S. Department of Energy (DOE) performed an engineering analysis based on the remaining design options

. The engineering analysis consists of estimating the energy consumption and costs of products at various levels of increased efficiency . This section provides an overview of the engineering analysis (section 5.1 ), discusses proposed equipment classes (section 5.2 ), establishes baseline unit specification s (section 5.4.1 ), discusses incremental efficiency levels (section 5.4.2 ), explains the methodology used during da ta gathering ( 5.5 ) and discusses the analysis and results (section 5.6 )

The primary inputs to the engineering analysis are baseline information from the market and technology assessment (c hapter 3 of this technical support document ( TSD )) and technology options from the screening analysis (chapter 4) Additional inputs include laboratory testing and

reverse

- engineering of representative equipment, energy modeling, and manufacturer interviews. The primary output of the engineering analysis is a set of cost- efficiency curves . In the subsequent markups analysis ( c hapter 6), DOE determined customer ( i.e.

, equipment purchaser) prices by applying distribution markups, sales tax and contractor markups. After applying these markups, they serve as the input to the building energy-use and end-use load c haracterization (chapter 7) and the life-cycle cost (LCC) and payback period (PBP) analyses ( c hapter 8).

DOE typically structures its engineering analysis around one of three methodologies. These are: (1) the design -option approach, which calculates the in cremental costs of adding specific design options to a baseline model that will improve its efficiency ( i.e. , lower its energy use); (2) the efficiency

- level approach, which calculates the relative costs of achieving increases in energy efficiency levels, without regard to the particular design options used to achieve such increases; and/or (3) the reverse

- engineering (or cost -assessment) approach, which provides “bottom-up” manufacturing cost assessments for achieving various levels of increased efficiency , based on teardown analyses (or physical teardowns) providing detailed data on costs for parts and material, labor, shipping/packaging, and investment for models that operate at particular efficiency levels. A supplementary method called a catalog teardow n uses published manufacturer catalogs and supplementary component data to estimate the major physical differences between a piece of equipment that has been physically disassembled and another piece of similar equipment for which catalog data are availabl e to determine the cost of the latter equipment. Deciding which methodology to use for the engineering analysis depends on the product, the design options under study, and any historical data that DOE can draw on.

5.2 EQUIPMENT CLASSES ANALYZED
DOE separated small, large, and very large, air

- cooled commercial package air conditioning and heating equipment (also referred to in this notice as small, large, and very large air -cooled commercial unitary air conditioners, CUAC, and small, large, and very large aircooled commercial unitary heat pumps, CUHP) into equipment classes

. Because DOE formulated a separate energy conservation standard for each equipment class, the criteria for separation into different classes are (1) type of energy used ( e.g., natural gas or electricity), and

5-1(2) capacity or other performance -related features such as those that provide utility to the consumer, or others deemed appropriate by the Secretary that would justify the establishment of a separate energy conservation standard

.
For th e reasons discussed in chapter 3 of this TSD , DOE has analyzed for the purposes of this final rule the equipment classes for small, large, and very large, air

- cooled CUAC and CUHP , presented in Table 5.2.1

.

Table 5.2.1 Proposed Equipment Classes Equipment Class Equipment Type Cooling Capacity Sub

Category Heating Type

1 Small Commercial Packaged Air

- Conditioning and Heating Equipment (Air

- Cooled) ≥ 65,000 Btu/h and <135,000 Btu/h AC Electric Resistance Heating or No Heating
2 All Other Types of Heating

3 HP Electric Resistance Heating or No Heating
4 All Other Types of Heating

5 Large Commercial Packaged Air

- Conditioning and Heating Equipment (Air

- Cooled) ≥ 135,000 Btu/h and <240,000 Btu/h AC Electric Resistance Heating or No Heating
6 All Other Types of Heating

7 HP Electric Resistance Heating or No Heating
8 All Other Types of Heating

9 Very Large Commercial Packaged Air

- Conditioning and Heating Equipment (Air

Cooled) ≥ 240,000 Btu/h and <760,000 Btu/h AC Electric Resistance Heating or No Heating
10 All Other Types of Heating

11 HP Electric Resistance Heating or No Heating
12 All Other Types of Heating

5.3 ENERGY EFFICIENCY METRIC
The current energy conservation standards for small, large, and very large air -cooled CUAC and CUHP are based on energy efficiency ratio (EER) for cooling efficiency and, for air

cooled CUHP heating efficiency, coefficient of performance (COP). 10 CFR 431.97(b).

5.3.1 Cooling Efficiency Metric

On February 1, 2013, DOE published a request for information and notice of document availability for sma ll, large, and very large, air cooled CUAC and CUHP . 78 FR 7296. In the RFI, DOE noted that it was considering whether to replace the existing efficiency descriptor

, EER, with a new energy

- efficiency descriptor, the integrated energy efficiency ratio ( IEER ).

As part of a final rule published on May 16, 2012, DOE amended the test procedure for this equipment to incorporate by reference the Air -Conditioning, Heating and Refrigeration Institute ( AHRI ) Standard 340/360–2007, “Performance Rating of Commercial a nd Industrial

5-2Unitary Air -Conditioning and Heat Pump Equipment,” including addendum 1 in December 2010 and addendum 2 in June 2011 (AHRI Standard 340/360–2007). 77 FR 28928. AHRI Standard 340/360–2007 includes methods and procedures for testing and rating equipment with both the EER and IEER metrics . EER is the ratio of the cooling capacity (in Btu/h) to the power input (in watts), and provides a measure of the efficiency of equipment operating at full load ( i.e. , 100 percent cooling capacity). IEER is a single number figure of merit expressing cooling part-load EER efficiency on the basis of weighted operation at various load capacities for the equipment. T he IEER metric factors in the efficiency of operating at part -loads of 75 percent, 50 percent, and 2 5 percent of capacity as well as the efficiency at full load. This is accomplished by weighting the full - and part

- load efficiencies with the average amount of time operating at each loading point. The IEER metric incorporates part load efficiencies measured with outside temperatures appropriate for the load levels, i.e. at lower temperatures for lower load levels.

EPCA authorizes DOE to establish “ energy conservation standards” that set either a single performance standard or a single design r equirement —not both. (42 U.S.C. 6311(18)) As such, DOE may prescribe an energy conservation standard based either on a single performance

based standard or design requirement. In the case of small, large, and very large air -cooled CUAC and CUHP

, the American Society of Heating, Refrigerating, and Air-Conditioning Engineers ( ASHRAE ) Standard 90.1–2010, “Energy Standard for Buildings Except Low- Rise Residential Buildings” (ASHRAE Standard 90.1–2010) specifies two performance requirements : EER and IEER a

. In DOE’s view, w ith respect to modifying its energy conservation standard with a new performance standard, the statute limits its choices to either an improved EER or a new standard using IEER. DOE did not consider altering its energy conservation standard to be based

on a single design requirement because performance -based standards will provide manufacturers with more flexibility in developing equipment that meets the standard levels rather than requiring a specific design. DOE notes that a change in metrics ( i.e. , from EER to IEER) would necessitate an initial DOE determination that the new requirement would not result in backsliding when compared to the current standards. (42 U.S.C. 6313(a)(6)(B)(iii)(I))

As part of the RFI, DOE conducted a review of the market to see if part

- load performance is currently being used and accepted for rating CUAC and CUHP. O n January 2, 2009, the Environmental Protection Agency (EPA) issued a draft ENERGY STAR specification for Light Commercial Air Conditioners and Heat Pumps equipment, i.e. , small and large air

cooled CUAC and CUHP, which proposed to adopt IEER as part of the minimum energy efficiency criteria. b In a January 30, 2009 letter regarding EPA’s draft

, AHRI supported this change. DOE also noted in the RFI that the Consortium for Energy Efficiency ( CEE ), an organization for energy efficiency advocates, has adopted IEER for its Tier 0, 1, and 2 efficiencies for CUAC and CUHP, i.e. , small, large, and very large air

- , water

- , and

a The IEER requirements were first established i n Addend a from the 2008 Supplement to Standard 90.1

– 2007, and became effective on January 1, 2010 . See ASHRAE Addenda. 2008 Supplement. http://www.ashrae.org/File%2 0Library/docLib/Public/20090317_90_1_2007_supplement.pdf
b ENERGY STAR. Re: EPA Proposed Draft Energy Star Specification for Light Commercial HVAC Equipment. http://www.energystar.gov/ia/partners/prod_development/revisions/downloads/lhvac/AHRI_Comments_D1.pdf

5-3evaporatively -cooled air conditioners and air- and water

- source heat pumps

. c 78 FR 7296, 7299 (Feb. 1, 2013).

DOE also noted in the RFI that IEER has gained support through efforts such as DOE’s Commercial Building Energy Alliance (CBEA) technology transfer program, which sponsors the High Performance Roof top Unit Challenge (RTU Challenge). This program provides a market mechanism that reduces barriers for manufacturers to procure greater than 18

- IEER 10 -ton equipment and encourages the private sector to commit to adopt energy

- efficient equipment. A number of manufacturers are currently participating in the RTU Challenge, including Lennox, 7AC Technologies, Rheem, Carrier, and McQuay. Of these participants, both Carrier and McQuay have already begun producing AHRI- certified equipment meeting or exceeding 18 IEER. In conjunction with manufacturer support, fourteen CBEA- member private entities, d such as Target Corp., Macy’s, Inc., McDonald’s Corp., and others, have also signaled their support and indicated their strong interest in potentially purchasing high-efficiency rooftop units, a sign of their confidence in the RTU Challenge and its ability to use IEER to accurately portray the energy use of air -cooled CUAC and CUHP in the field. 78 FR 7296, 7299 (Feb. 1, 2013).

As part of the RFI, DOE conducted a market analysis to compare the two metrics based on publicly available ratings of existing equipment currently available in the market. DOE made a document available for comment that provided the methodology and results of the investigation of the relationship be tween IEER and EER for air -cooled CUAC and CUHP with cooling capacities between 65,000 Btu/hr and 760,000 Btu/hr ( i.e. , 5 and 63 tons). e In the RFI, DOE noted that if it decides to propose standards using the IEER metric, it would transition the existing Federal energy conservation standards that are based on the EER metric to the new IEER metric to determine baseline energy -efficiency levels to use in the analysis. 78 FR 7296, 7299 (Feb. 1, 2013).

EPCA requires that test procedures be reasonably designed to produce test results that measure the energy efficiency of covered equipment during a representative average use cycle or period of use. (42 U.S.C. 6314(a)(2)) As discussed above, the IEER metric weights the efficiency of operating at different part loads and full load based on usage patterns, which provide a more representative measure of annual energy use than the EER metric. A manufacturer that was involved in the development of the IEER metric indicated that the usage patterns weights for the IEER metric were developed by analyzing equipment usage patterns of several buildings across the 17 ASHRAE Standard 90.1–2010 (appendix B) climate zones identified. ( Docket ID: EERE –2013– BT

– STD –0007–0018, Carrier, at p. 1) The weighting factors accounted the h ours of operation where mechanical cooling was active. Id

. As a result, the IEER metric provides a more accurate representation of the annual energy use for this equipment than the EER metric , which only considers full load energy use. For the reasons , DO E is proposing energy conservation standards based on the IEER metric.

c Consortium for Energy Efficiency. CEE Commercial Unitary AC and HP Specification. http://www.cee1.org/files/CEE_CommHVAC_UnitarySpec2012.pdf
d U.S. Department of Energy. Building Technologies Program. High Performance Rooftop Unit Challenge Fact Sheet. http://apps1.eere.energy.gov/buildings/publications/pdfs/alliances/techspec_rtus.pdf

e The document is available at: http://www1.eere.energy.gov/buildings/appliance_standards/product.aspx/productid/77

. 5-45.3.2 Heating Efficiency Metric AHRI Standard 340/360–2007 also specifies methods and procedures for testing and rating equipment heating efficiency for air -cooled CUHP based on the COP metric. The heating efficiency COP is the ratio of the heating capacity (in watts) to the power input (in watts). f AHRI Standard 340/360–2007 provides methods to rate the COP at both high temperature steady state heating conditions (47 degrees Fahrenheit (°F) dry bulb and 43 °F wet bulb) and low temperature steady state heating conditions (17 °F dry bulb and 15 °F wet bulb). The current energy conservation standards for small, large, and very large air-cooled CUHP heating efficiency are based on the COP met ric rated at the high temperature steady state heating conditions. 10 CFR 431.97(b)

DOE is not aware of any test procedures that have been developed that measure part load performance in heating mode for small, large, and very large air -cooled CUHP. DOE is not aware of any data regarding the annual usage for CUHP under part -load heating conditions to determine whether part -load heating hours are significant and would warrant the development of a part

- load heating metric. One manufacturer noted that CUHP typically operate in full load heating mode and cycle the auxiliary heat on and off because heat pump capacity alone is inadequate to meet the building load. In addition, DOE is unaware of data regarding usage patterns for CUHP to determine appropriate test c onditions under part-load heating conditions. Because DOE is unaware of any test procedures or usage data regarding part

- load performance in heating mode for CUHP that shows that part-load heating hours are significant, DOE is not considering amendments to the test procedure to measure part

- load heating efficiency at this time. DOE is proposing standards for the heating efficiency based on the COP metric.

5.4 EFFICIENCY LEVELS

5.4.1 Baseline Units DOE selected baseline units as reference points for each equipment class, against which DOE measured changes resulting from energy conservation standards

. The baseline unit in each equipment class represents the basic characteristics of equipment in that class

. Typically, a baseline unit is a unit that just meets current required energy conservation standards and provides basic consumer utility . DOE used the baseline units in the engineering analysis and the lifecycle

- cost and payback

- period analysis . To determine energy savings and changes in price, DOE compared each higher energy efficiency design option with the baseline unit.

As discussed in section 5.3.1

, DOE is proposing to replace the current cooling performa nce energy efficiency descriptor ( i.e.
, EER ), with a new energy efficiency descriptor ( i.e.
, IEER ) , and a single EER level can correspond to a range of IEERs. As a result, DOE must establish a baselin e IEER for each equipment class. DOE is typically obligated either to adopt those standards developed by ASHRAE or to adopt levels more stringent than the ASHRAE levels if there is clear and convincing evidence in support of doing so. (42 U.S.C. 6313(a)(6)(A) ) ASHRAE Standard 90.1–2010 specifies minimum efficiency requirements using both the EER and IEER metrics. As discussed in the RFI, DOE evaluated the relationship between EER and

f Any supplementary resistance heat is excluded from the test

. 5-5IEER by considering models that are rated at the current DOE standard levels based on the EER metric for each equipment class. DOE then analyzed the distribution of corresponding rated IEER values for each equipment class. DOE notes that the lowest IEER values associated with the current DOE standards for EER generally correspond with the ASHRAE Standard 90.1–2010 minimum efficiency requirements. 78 FR 7296, 7299 (Feb. 1, 2013); EERE-2013- BT

- STD

0007-0001. Based on this evaluation, because DOE is considering energy conservation standards based on the IEER metric, DOE is proposing to use the ASHRAE Standard 90.1–2010 minimum IEER requirements to characterize the baseline cooling efficiency for each equipment class. DOE also notes that equipment is available on the market that is at or near the ASHRAE Standard 90.1–2010 minimum IEER requirements. As a result, DOE is not considering higher IEER levels for the baseline.

As discussed in section 5.3.2

, DOE is considering heating efficiency standards for CUHP based on the COP metric. The Energy Policy Act of 2005, Public Law 109–58 (Aug. 8, 2005) (EPAct 2005) established minimum COP levels for small, large, and very large air -cooled CUHP , which DOE codified in a final rule on October 18, 2005. 70 FR 60407. DOE i s proposing
to use the COP standard levels to characterize the baseline heating efficiency for each equipment class.

The baseline efficiency levels for each equipment class are presented below in Table 5.4.1

.

Table 5.4.1 Baseline Efficiency Levels

Equipment Type Heating Type Baseline Efficiency Level

Small Commercial Packaged AC and HP (Air

- Cooled) – ≥ 65,000 Btu/h and <135,000 Btu/h Cooling Capacity AC Electric Resistance Heating or No Heating 11.4 IEER
All Other Types of Heating 11.2 IEER

HP Electric Resistance Heating or No Heating 11.2 IEER 3.3 COP All Other Types of Heating 11.0 IEER 3.3 COP

Large Commercial Packaged AC and HP (Air

- Cooled) – ≥ 135,000 Btu/h and <240,000 Btu/h Cooling Capacity AC Electric Resistance Heating or No Heating 11.2 IEER
All Other Types of Heating 11.0 IEER

HP Electric Resistance Heating or No Heating 10.7 IEER 3.2 COP All Other Types of Heating 10.5 IEER 3.2 COP

Very Large Commercial Packaged AC and HP (Air

Cooled) – ≥ 240,000 Btu/h and <760,000 Btu/h Cooling Capacity AC Electric Resistance Heating or No Heating 10.1 IEER
All Other Types of Heating 9.9 IEER

HP Electric Resistance Heating or No Heating 9.6 IEER 3.2 COP All Other Types of Heating 9.4 IEER 3.2 COP

5-65.4.2 Incremental Efficiency Levels For the equipment classes presented in section 5.2 , DOE analyzed several efficiency levels and obtained incremental cost data at each of these levels

. Table 5.4.2 presents the efficiency levels for each equipment class.

As part of the NOPR analyses, DOE considered four efficiency levels beyond the baseline efficiency level for each equipment class. These levels were developed primarily b ased on a review of industry standards and available equipment. For efficiency level (EL) 1, DOE used the IEER levels specified in a draft of addendum CL g to ASHRAE Standard 90.1–2010 (Draft Addendum CL) . For the higher efficiency levels, DOE initially determined the levels for equipment classes of CUAC with electric resistance heating or no heating based on the range of efficiency levels associated with equipment listed in the AHRI certification database h and the California Energy Commission’s (CEC) database i . DOE evaluated the full range of capacities for the small, large, and very large equipment classes with specific focus on 7.5-ton, 15-ton, and 30- ton as the representative cooling capacities (see sec tion 5.6 ) . DOE chose efficiency levels for CUAC with all other types of heating equal to the efficiency levels for equipment with electric resistance heating or no heating , minus the differences in the IEER specifications for these pairs of equipment classes prescribed in the Draft Addendum CL . DOE believes these decreases in IEER appropriately reflect the additional power required for furnace pressure drop. Similarly for the CUHP equipment classes, DOE developed cooling mode efficiency levels equal to the CUAC efficiency levels minus the difference in IEER specifications for these two equipment types prescribed in the Draft Addendum CL . DOE believes t hat the se decreases in IEER are representative of the efficiency differences that occur due to losses from the reversing valve and coil circuitry required in heat pumps.

T he maximum

- available efficiency levels rely on the performance of recently introduced models. DOE evaluated available equipment literature and energy use information on these maximum

- available efficiency models and conducted energy modeling to determine the feasibility of achieving these efficiency levels. For the ≥65,000 Btu/h and <135,000 Btu/h capacity CUAC with electric resistance heating or no heating equipment classes, DOE noted based on its review of the AHRI certification and CEC equipment databases that the maximum

available unit was rated at 20.9 IEER. However, sufficient information allowing correlation of incremental efficiency gain s with specific design options and incremental manufacturing costs was not available to properly evaluate this unit. DOE also notes that a different manufacturer currently offers a 7.5-ton model rated at 19.9 IEER and a 10-ton model rated at 20.8 IEER. DOE notes that there is also uncertainty regarding the way the design differences contribute to the added efficiency of the 10

- ton model, making it difficult to accurately estimate the incremental
cost as sociated with this efficiency gain. As a result, DOE is proposing to use 19.9 IEER as the maximum

- available efficiency level representative of this equipment class. DOE is not aware of

g ASHRAE periodically updates specifications in its Standard 90.1through a public review process. The Draft Addendum CL

, which was made available for public review in October 2012

, was the latest available version at the time DOE conducted the analyses for today’s NOPR. DOE notes that ASHRAE has more recently finalized Addendum CL, with minor modifications to the IEER levels for large air

- cooled CUAC and CUHP (i.e., cooling capacity of >=135,000 Btu/h and <240,000 Btu/h).
h Available online at: http://www.ahridirectory.org/ahridirectory/pages/home.aspx

. i Available online at: http://www.appliances.energy.ca.gov/Default.aspx

. 5-7data showing that energy efficiency can be increased beyond these level s. As a result, DOE is proposing to use the maximum- available efficiency levels as the max

- tech levels for the NOPR analyses.

For the CUHP equipment classes, DOE is proposing heating efficiency levels based on the variation of COP with IEER. In the advanced notice of proposed rulemaking (ANOPR) that was published on July 29, 2004 (hereafter referred to as the July 2004 ANOPR), DOE proposed to address the energy efficiency of air -cooled CUHP by developing functions relating COP to EER. 69 FR 45460, 45468 (July 29, 2004). This method was also used by industry to establish minimum performance requirements for ASHRAE Standard 90.1–1999. Id. AHRI supplied the ASHRAE Standard 90.1–1999 committee with curves relating the COP as a function of EER. Using this information, the committee then set the minimum COP levels to the COP corresponding to the selected minimum EER level. Id. DOE stated in the RFI that since this method was generally accepted by industry and interested parties involved in the development of ASHRAE Standard 90.1–1999, it was considering a similar approach for this rulemaking. DOE indicated that if it transitions to IEER as the cooling mode energy efficiency descriptor, DOE may establish minimum COP levels based on the variation of COP with IE ER. 78 FR 7296, 7301 (Feb. 1, 2013).

To determine COP efficiency levels, DOE evaluated AHRI and CEC data for small, large, and very large air

- cooled CUHP units with electric resistance heat or no heat to analyze the relationship between COP and both IEER a nd EER. DOE developed linear relationships between EER and COP, and IEER and COP through regression. Figure 5.4.1 through Figure 5.4.3 show the relationships between EER and COP. Figure 5.4.4 through Figure 5.4.6 show the relationships between IEER and COP.

Figure 5.4.1 Relationship between EER and COP for Heat Pump, ≥65,000 Btu/h and <135,000 Btu/h Cooling Capacity, Electric Heat/No Heating Equipment Class

5-8Figure 5.4.2 Relationship between EER and COP for Heat Pump, ≥135,000 Btu/h and <240,000 Btu/h Cooling Capacity, Electric Heat/No Heating Equipment Class

Figure 5.4.3 Relationship between EER and COP for Heat Pump, ≥240,000 Btu/h and <760,000 Btu/h Cooling Capacity, Electric Heat/No Heating Equipment Class

5-9Figure 5.4.4 Relationship between IEER and COP for Heat Pump, ≥65,000 Btu/h and <135,000 Btu/h Cooling Capacity, Electric Heat/No Heating Equipment Class

Figure 5.4.5 Relationship between EER and COP for Heat Pump, ≥135,000 Btu/h and <240,000 Btu/h Cooling Capacity, Electric Heat/No Heating Equipment Class

5-10Figure 5.4.6 Relationship between EER and COP for Heat Pump, ≥240,000 Btu/h and <760,000 Btu/h Cooling Capacity, Electric Heat/No Heating Equipment Class DOE’s review of the data showed that the correlations between COP and IEER using linear regressions are no less strong than the correlations between COP and EER for e ach cooling capacity range. Based on this evaluation, DOE is proposing to use the functions relating COP to IEER based on AHRI and CEC data to establish COP efficiency levels. For each CUHP equipment class, DOE selected COP levels corresponding to each inc remental IEER level.

The efficiency levels for each equipment class are presented in Table 5.4.2

.

5-11Table 5.4.2 Incremental Efficiency Levels

Equipment Type Heating Type Efficiency Levels

Baseline EL1 EL2 EL3 EL4 (Max

- Tech)

Small Commercial Packaged AC and HP (Air

- Cooled) – ≥65,000 Btu/h and <135,000 Btu/h Cooling Capacity AC Electric Resistance Heating or No Heating 11.4 IEER 12.9 IEER 14 IEER 14.8 IEER 19.9 IEER

All Other Types of Heating 11.2 IEER 12.7 IEER 13.8 IEER 14.6 IEER 19.7 IEER

HP Electric Resistance Heating or No Heating 11.2 IEER 3.3 COP 12.2 IEER 3. 3 COP 13.3 IEER 3.4 COP 14.1 IEER 3.5 COP 19.2 IEER 3.7 COP

All Other Types of Heating 11.0 IEER 3.3 COP 12 IEER 3. 3 COP 13.1 IEER 3.4 COP 13.9 IEER 3.4 COP 19.0 IEER 3.6 COP

Large Commercial Packaged AC and HP (Air

- Cooled)

– ≥135,000 Btu/h and <240,000 Btu/h Cooling Capacity AC Electric Resistance Heating or No Heating 11.2 IEER 12.2 IEER 13.2 IEER 14.2 IEER 18.4 IEER

All Other Types of Heating 11.0 IEER 12.0 IEER 13.0 IEER 14.0 IEER 18.2 IEER

HP Electric Resistance Heating or No Heating 10.7 IEER 3.2 COP 11.4 IEER 3. 2 COP 12.4 IEER 3.3 COP 13.4 IEER 3.3 COP 17.6 IEER 3.3 COP

All Other Types of Heating 10.5 IEER 3.2 COP 11.2 IEER 3. 2 COP 12.2 IEER 3.3 COP 13.2 IEER 3.3 COP 17.4 IEER 3.3 COP

Very Large Commercial Packaged AC and HP (Air

- Cooled) – ≥240,000 Btu/h and <760,000 Btu/h Cooling Capacity AC Electric Resistance Heating or No Heating 10.1 IEER 11.6 IEER 12.5 IEER 13.5 IEER 15.5 IEER

All Other Types of Heating 9.9 IEER 11.4 IEER 12.3 IEER 13.3 IEER 15.3 IEER

HP Electric Resistance Heating or No Heating 9.6 IEER 3.2 COP 10.6 IEER 3.2 COP 11.5 IEER 3.2 COP 12.5 IEER 3.2 COP 14.5 IEER 3.2 COP

All Other Types of Heating 9.4 IEER 3.2 COP 10.4 IEER 3.2 COP 11.3 IEER 3.2 COP 12.3 IEER 3.2 COP 14.3 IEER 3.2 COP

5.5 METHODOLOGY OVERVIEW
In order to develop the cost- efficiency relationships f or small, large, and very large, air

cooled CUAC and CUHP, DOE conducted testing and performed detailed equipment teardowns and reverse- engineering analyses on a sample of models to develop a manufacturing cost model. In addition, DOE supplemented the teardown analysis by conducting catalog teardowns for equipment spanning the full range of capacities from all manufacturers selling equipment in the United States. DOE conducted energy modeling analyses to identify key design features required to achieve higher efficiency levels , consistent with equipment available on the market. The energy modeling was used in conjunction with the manufacturing cost model to determine the incremental costs associated with higher

- efficiency equipment design to develop the cost5-12efficiency relationships . DOE also supplemented these analyses by conducting interviews with equipment manufacturers to gain a better understanding of the design options and costs associated with achieving higher efficiency levels.

5.5.1 Manufacturer Interviews

DOE conducted confidential interviews with manufacturers of small, large, and very large, air -cooled CUAC and CUHP to develop a deeper understanding of the various combinations of technologies used to increase equipment efficiency

, and their associated manufacturing costs . Sample questions asked during the interviews, which were also conducted in support of the manufacturer impact analysis, are contained in appendix 5A. During the interviews, DOE also gathered information about the capital expenditures required to increase the efficiency of the baseline units to various efficiency levels ( i.e. , conversion capital expenditures by efficiency or energy -use level) . The interviews provided information about the size and the nature of the c apital investments . DOE also requested information about the depreciation method used to expense the conversion capital.

5.5.2 Equipment Teardown Other than obtaining detailed manufacturing costs directly from a manufacturer, the most accurate method for determi ning the production cost of a piece of equipment is to disassemble the equipment piece- by

- piece and estimate the material and labor cost of each component using a process commonly called a physical teardown

. A supplementary method, called a catalog teardow n, uses published manufacturer catalogs and supplementary component data to estimate the major physical differences between a piece of equipment that has been physically disassembled and another piece of similar equipment. DOE performed physical and catalo g teardown analys es on equipment for this rulemaking. The teardown methodology is described in detail in section 5.5.2.1 through section 5.5.2.3

.

5.5.2.1 Selection of Units During the process of selecting units for teardown, DOE considers three main questions:

• What efficiency levels should b e captured in the teardown analysis?

• Are there units on the market that capture all potential efficiency levels and design options?

• Which of the available units are most representative?
In responding to the preceding questions, DOE adopts the following cri teria for selecting units for the teardown analysis:

• The selected products should span the full range of efficiency levels for each equipment class under consideration;

• W ithin each equipment class, if possible, the selected products should come from the

sa me manufacturer and be within the same equipment series;

5-13• T he selected equipment should primarily come from manufacturers with large market share in that equipment class, although the highest efficiency equipment were chosen irrespective of manufacturer; an d

• T he selected equipment should have non- efficiency

- related features that are the same as, or similar to, features of other equipment in the same class and at the same efficiency level

.

5.5.2.2 Generation of Bill of Materials

The end result of each teardown is typ ically a structured bill of materials (BOM)

. Structured BOMs describe each equipment part and its relationship to the other parts, in the estimated order of assembly . The BOMs describe each fabrication and assembly operation in detail, including the type of equipment needed ( e.g. , stamping presses, injection molding machines, spot- welders, etc.) and the process cycle times . The result is a thorough and explicit model of the production process.

The BOMs incorporate all materials, components, and fasteners

, classified as either raw materials or purchased parts and assemblies

. The classification into raw materials or purchased parts is based on DOE’s previous industry experience, recent information in trade publications, and discussions with high- and low-volume original equipment manufacturers (OEMs).

For purchased parts, the purchase price is an estimate based on volume- variable price quotations and detailed discussions with suppliers. For fabricated parts, the price of intermediate materials ( e.g. , tube, s heet metal) and the cost of transforming them into finished parts are an estimate based on current industry pricing.

The cost of raw materials is determined using prices for copper, steel and aluminum from the American Metals Market. 1 The price of steel drastically increased in 2005, and the price of
copper has increased steadily since 2004. Because DOE is using a 5- year average in material prices from 2009–2013 , these price increases are normalized, which better represents long

- term material prices.

5.5.2.3 Cost Structure of the Spreadsheet Models The manufacturing cost assessment methodology used is a detailed, component-focused technique for rigorously calculating the manufacturing cost of a product (direct materials, direct labor and some overhead costs. ) Figu re 5.4.1 shows the three major steps in generating the manufacturing cost.

5-14Figure 5.5.1 Ma nufacturing Cost Assessment Stages The first step in the manufacturing cost assessment is the creation of a complete and structured BOM from the disassembly of the units selected for teardown. The units are dismantled, and each part is characterized according to weight, manufacturing processes used, dimensions, material , and quantity. The BOM incorporates all materials, components, and fasteners with estimates of raw material costs and purchased part costs . Assumptions on the sourcing of parts and in-house fabrication are based on industry experience, information in trade publications, and discussions with manufa cturers

. Interviews and plant visits are also conducted with manufacturers to ensure accuracy on methodology and pricing.

Following the development of a detailed BOM, the major manufacturing processes are identified and developed for the spreadsheet model. These processes are listed in Table 5.5.1

.

Table 5.5.1 Major Manufacturing Processes

Fabrication Finishing Assembly/Joining Quality Control Fixturing Washing Adhesive Bonding Inspecting & Testing Stamping/Pressing Powder Coating Spot Welding Turret Punching De

- burring Seam Welding Brake Forming Polishing Brazing Cut ting and Shearing Tube Forming Fabrication process cycle times are estimated and entered into the BOM . For this analysis, $24.00 per hour was used as the average fully-burdened labor rate based on typical annual wages and benefits of industry employees. In the final step of the cost assessment, assembly times and associated direct labor costs are estimated

. Once the cost estimate for each teardown unit is finalized, a detailed summary is prepared for relevant components, subassemblies and processes. The B OM thus details all aspects of unit costs.

Design options used in units subject to teardown are noted in the summary sheet of each cost model and are cost

- estimated individually . Thus, various implementations of design options can be accommodated, ranging from assemblies that are entirely purchased to units that are made entirely from raw materials . Hybrid assemblies, consisting of purchased parts and parts made on site are thus also accommodated

.

5.5.3 Shipping Costs
In addition to the MPC, DOE also considered the cost to ship the unit from the manufacturing facility to the first point on the distribution chain. In calculating the shipping costs, DOE first gathered estimates of the costs to ship a full trailer of manufactured equipment an average distance in the United States. DOE then used the representative unit sizes to calculate

5-15a volume for each unit. Along with the dimensions of a shipping trailer, DOE used this cost and volume information to develop an average shipping cost for each equipment class direct ly analyzed.

5.5.4 Equipment Testing DOE conducted equipment testing to verify the energy use of equipment and to develop a better understanding of the potential efficiency improvements associated with various design options and to develop disaggregated efficien cy data . The equipment testing also served to provide information about the refrigeration system operating conditions to support the energy modeling analyses.

5.6 ANALYSIS AND RESULTS
DOE conducted the engineering analyses using the reverse

- engineering approac h, analyzing three specific capacities to represent each of the three cooling capacity categories ( i.e.
, small, large, and very large). Based on a review of manufacturer equipment offerings and interviews with manufacturers, DOE selected representative capacities of 90,000 Btu/h (7.5
tons j ) for the ≥65,000 to <135,000 Btu/h capacity range, 180,000 Btu/h (15 tons) for the ≥135,000 to <240,000 Btu/h capacity range, and 360,000 Btu/h (30 tons) for the ≥240,000 to <760,000 Btu/h capacity range. k DOE noted in the July 2004 ANOPR that 7.5 tons and 15 tons represent capacity points with large shipment volumes in their respective capacity range. 69 FR 45460, 45469 (July 29, 2004). T hese capacities are near the center of their respective equipment class capacity r anges. Additionally, as discussed in section 5.6.1

, DOE interviewed several equipment manufacturers as part of the current rulemaking and found that the majority of manufacturers interviewed agreed that the 7.5-ton, 15-ton, and 30- ton capacities adequately represent the three equipment class capacity ranges.

5.6.1 Manufacturer Interviews As previously discussed in section 5.5.1 , DOE conducted confidential interviews with CUAC and CUHP manufacturers. Sample questions are contained in appendix 12A. In general, manufacturer s interviewed agreed with DOE’s proposed methodology of evalua ting a representative size unit for each equipment class, specifically 7.5 ton to represent small capacity units, 15 ton to represent large capacity units, and 30 tons to represent very large capacity units. Manufacturers indicated that the three capacity sizes DOE proposed to investigate generally have high sales volume. Some manufacturers remarked that DOE should evaluate both air conditioning units and heat pump.

During the interviews, manufacturers indicated that the IEER metric was relatively new and expressed concern over testing variab ility and the robustness of the metric. Regarding the proposed methodology for evaluating different efficiency levels, manufacturers remarked that DOE should evaluate different size and efficiency equipment from the sam e manufacturer(s) and

j Air conditioning cooling capacity may be denoted in tons. An air conditioning ton is equivalent to 12,000 Btu/h of cooling capacity (or 3.5 kilowatts of cooling capacity).
k An air conditioning ton is equivalent to 12,000 Btu/h of coo ling capacity.

5-16product family. Manufacturers interviewed did not oppose DOE’s proposal to conduct a reverse engineering analysis.

From the manufacturers interviewed, DOE collected a general impression of commercial air -cooled air conditioning and heating equipment on the market. Interviewed manufacturers indicated that all of the equipment covered in this rulemaking currently use scr oll compressors and R-410A refrigerant . However, manufacturers employ different design strategies in terms of compressor staging, indoor and outdoor fan selection, and heat exchanger design. Manufacturers interviewed noted that technologies like variable speed drives and compressor staging could be employed to achieve higher IEER , however, manufacturers did no t quantify the improvement potential of these technologi es. Manufacturers also commented that although increasing the size of the heat exchangers in a unit increase s efficiency, this approach has diminishing returns ( i.e.
, the size increase that achieves 5 percent improvement would have to be more than doubled to achieve 10 percent improvement) . Additionally, manufacturers remarked that CUACs and CUHPs are limited in terms of footprint size because the units are often installed on existing rooftop curbs. A rooftop curb is a mounting platform that provides structural support, weight distribution, and a level installation surface and DOE understood from the manufacturers interviewed that changing the size of a rooftop curb can be costly. CUACs and CUHPs are generally shipped by freight truck , which also imposes a s ize limit. Regarding installation, maintenance, and repair costs, manufacturers thought that an increase in efficiency level would likely cause units to become more complex and therefore more expensive to install, maintain, and repair.

5.6.2 Equipment Testing
As discussed above, DOE conducted the engineering analyses specifically analyzing representative capacities of 7.5 tons, 15 tons, and 30 tons. DOE conducted a market survey of small, large, and very large air -cooled CUAC and CUHP models and their features. DOE selected four 7.5 -ton, two 15-ton, and one 30-ton CUAC models for testing and reverse engineering. The models were selected to develop a representative sample of the market at different efficiency levels. DOE based the selection of units on the efficiency data available in the AHRI certification database and the CEC equipment database. Where feasible, DOE selected models for reverse engineering with low and high efficiencies from a given manufacturer that are built on the same platform ( i.e. , the same basic design and construction). DOE also selected one 7.5-ton CUHP model to evaluate the design differences between CUAC units and CUHP units. Details of the key features of the tested units are presented in Table 5.6.1

.

5-17Table 5.6.1 Small Air

- Cooled CUAC and CUHP Test Units

Feature Test Unit Description

CUAC

– Electric Resistance Heating or No Heating CUHP

– Electric Resistance Heating or No Heating

Test Unit 1 Test Unit 2 Test Unit 3 Test Unit 4 Test Unit 5 Rated Cooling Tons 7.5 7.5 7.5 7.5 7.5 Cooling Stages 1 2 1 2 2

Rated IEER 11.4 13.2 12.2 14.5 12.8

Rated EER 11.2 12.2 11.2 12.6 12.1

Rated COP

- - - - 3.5

Compresso

r Quantity 1 2 1 2 2

# of Circuits 1 2 1 2 2

Type Scroll Scroll Scroll Scroll Scroll

Outdoor Coil Quantity 1 1 1 1 1

Type Fin

- and

tube Fin

- and

tube Microchannel Microchannel Fin

- and

- tube

Face Area (ft. 2 ) 20.5 25.1 16.91 20.66 25.1

Fin Pitch 17 17 23 23 17

Tube Rows 2 2 1 1 2

Outdoor Fan Quantity 2 2 1 1 2

Motor Horse p ower 0.25 0.25 0.7 0.75 0.25

Speeds 1 1 1 2 1

Indoor Coil Quantity 1 1 1 1 1

Type Fin

- and

tube Fin

- and

tube Fin

- and

- tube Fin

- and

- tube Fin

- and

- tube

Face Area (ft. 2 ) 8.9 11.1 9.89 12.36 11.1

Fin Pitch 15 15 16 16 15

Tube Rows 3 4 4 4 4

Indoor Fan # of Motors/ # of Fans 1/1 1/1 1/1 1/1 1/1

Drive Belt Belt Belt Direct Belt

Motor Horse p ower 1.7 1.7 1 3.75 1.2

Speeds 1 1 3 Variable Speed 1

5-18Table 5.6.2 Large and Very Large Air

- Cooled CUAC and CUHP Test Units

Feature Test Unit Description

CUAC

– Electric Resistance Heating or No Heating

Test Unit 6 Test Unit 7 Test Unit 8 Rated Cooling Tons 15 15 30 Cooling Stages 2 2 2

Rated IEER 13.2 Not Listed 11.9

Rated EER 12.2 11.0 10.1

Compressor Quantity 2 2 4

# of Circuits 2 2 2

Type Scroll Scroll Scroll

Outdoor Coil Quantity 2 2 1 Type Fin

- and

- tube Fin

- and

- tube Microchannel

Face Area (ft. 2 ) 21.4 (each) 20.19 (each) 32.9

Fin Pitch 17 21 20

Tube Rows 2 2 1

Outdoor Fan Quantity 3 3 2

Motor Horse p ower 0.25 0.33 1

Speeds 1 1 1

Indoor Coil Quantity 1 1 1 Type Fin

- and

- tube Fin

- and

- tube Fin

- and

- tube

Face Area (ft. 2 ) 22 16.34 31. 7

Fin Pitch 15 15 15

Tube Rows 4 3 4

Indoor Fan # of Motors/ # of Fans 1/2 1/1 1/2

Drive Belt Belt Belt

Motor Horse p ower 2.2 2 10

Speeds 1 1 1

Because DOE is considering energy conservation standards based on the IEER metric, DOE conducted testing on each unit according to the IEER test method specified in AHRI Standard 340/360–2007. Table 5.6.3 shows the test results of selected small, large and very large CUAC and CUHP units. The maximum deviation of tested and rated cooling capacity is observed to be -7.9 percent. The maximum deviations of tested EER and IEER compared to rated EER and IEER are -4.4 percent and 12.9 percent, respectively.

5-19Table 5.6.3 Test Results of Selected Small, Large and Very Large CUAC and CUHP units

Parameter Te st Unit 1 Test Unit 2 Test Unit 3 Test Unit 4 Test Unit 5 Test Unit 6 Test Unit 7 Test Unit 8

Type CUAC CUAC CUAC CUAC CUHP CUAC CUAC CUAC

Nominal Cooling Capacity [ton] 7.5 7.5 7.5 7.5 7.5 15 15 30

Rated IEER 11.4 13.2 12.2 14.5 12.8 13.2 13 11.9
Rated EER 11.2 12.2 11.2 12.6 12.1 12.2 11 10.1

Tested Cooling Capacity [ton] 7.8 7.4 7.2 7.6 7.6 14.8 14.9 2 7.6 c

Tested IEER 12.9 14.0 13.2 15.4 a 13.3 13.2 NA b 11.2 c
Tested EER 11.5 12.4 11.6 12.4 11.6 11.9 10.5 10.0 c

a Corrected through energy modeling at 75 percent load point.
b Tested for IPLV instead of IEER prior to this rulemaking.

c Corrected indoor blower air flow rate to meet minimum static pressure requirement.

5.6.3 Equipment Teardown As part of the reverse engineering analyses, DOE conducted physical teardowns on each test unit l to develop a manufacturing cost model and to evaluate and identify key details for design features ( e.g. , heat exchangers, compressors, fan and fan motors, con trol strategies, etc.) and the corresponding manufacturing cost of each test unit. Because DOE was only able to conduct testing and physical teardowns on a limited sample of equipment, DOE supplemented th ese data by conducting catalog teardowns on 346 models spanning the full range of capacities and efficiency levels from all manufacturers selling equipment in the United States. DOE based the catalog teardowns on information provided in equipment literature and experience from the physical teardowns.

Based upon product teardowns (supplemented by the energy modeling and design option analysis discussed in section s 5.6.4 and 5.6.5 ), DOE developed the following baseline production cost distributions and materials costs distributions for typical small, large, and very large air

cooled CUACs, shown in Figure 5.6.1 through Figure 5.6.6 . Depend ing on the manufacturer and the production volume, the depreciation costs may vary from those shown in the figures, which assume a “green

- field” site. Production cost distributions include raw material, purchased part, labor (assembly, fabrication, supervision, and indirect labor), depreciation (equipment, tooling, and building depreciation), and other overhead (indirect process, maintenance, utility, property tax, and insurance ) costs

. Mate rial cost distributions are broken down by major assemblies ( e.g. , structural sheet metal, indoor/outdoor heat exchangers and fan assemblies, sealed system, controls). DOE note s that the refrigeration system, heat exchangers, and fan components account for over 69 percent of the material costs for this equipment.

l For test unit #8, DOE conducted a partial teardown, examining key components (heat exchangers, compressors, fans/motors, controls, etc.) and basic design construction without fully disassembling the unit.

5-20Figure 5.6.1 Baseline 7.5- Ton Air

- Cooled CUAC Full Production Cost Distribution

Figure 5.6.2 Ba seline 7.5

- Ton Air

- Cooled CUAC Materials Cost Distribution

5-21Figure 5.6.3 Baseline 15

- Ton Air

- Cooled CUAC Full Production Cost Distribution

Figure 5.6.4 Baseline 15

- Ton Air

- Cooled CUAC Materials Cost Distribution

5-22Figure 5.6.5 Baseline 30

- Ton Air

- Cooled CUAC Full Production Cost Distribution

Figure 5.6.6 B aseline 30

- Ton Air

- Cooled CUAC Materials Cost Distribution

5-23Based on the physical/catalog teardowns, DOE evaluated the relationship between heat transfer area and IEER for both the indoor and outdoor coils. m Figure 5.6.7 through Figure 5.6.12 show the coil face area multiplied by the number of tube row for indoor and outdoor coils, respectively , for 7.5- ton, 15 -ton, and 30-ton units. n DOE observed that the increased heat transfer area generally correlated with higher IEER values.

Figure 5.6.7 7.5-ton Indoor Coil Face Area * Number of Tube Rows versus IEER

m The following are examples of equipment literature DOE reviewed (does not include complete list of analyzed literature): (1) United Technologies Corporation. “Carrier 50TC Cooling Only/Electric Heat, Packaged Rooftop, 3 to 15 Nominal Tons: Product Data.” Available online at: http://www.docs.hvacpartners.com/idc/groups/public/documents/techlit/50tc

- 19pd.pdf (Accessed on Sept. 12, 2013). (2) Lennox International Inc. “Lennox Packaged Electric /Electric LCH Energence® Rooftop Units: Product Specifications.” Available online at: http://tech.lennoxintl.com/C03e7o14l/3rEpIb5d/ehb_lch_bbox_1306_210556_020.pdf (Accessed on Sept. 12, 2013). (3) Ingersoll Rand. “Trane Product Catalog: Packaged Rooftop Air Conditioners, VoyagerTM Cooling and Gas/Electric, 12 1⁄2 - 25 Tons, 60Hz“ Available online at: http://www.trane.com/CPS/Uploads/UserFiles/DXUnitarySystems/Light%20Rooftops/RT

- PRC028

- EN_08022013.pdf (Accessed on Sept. 12, 2013).

n For the 7.5

- ton and 15

- ton units, DOE evaluated heat transfer area versus IEER for units with tube

- and

- fin heat exchangers (for both the outdoor and indoor coils) to provide a consistent evaluation of coil sizes. For 30

- ton units, because the majority of units on the market used microchannel heat exchangers for the outdo or coil, DOE evaluated heat transfer area versus IEER for units with microchannel heat exchangers for the outdoor coils and tube

- and

- fin heat exchangers for the indoor coils.

5-24Figure 5.6.8 7.5- ton Indoo r Coil Face Area * Number of Tube Rows versus IEER

Figure 5.6.9 15-ton Indoor Coil Face Area * Number of Tube Rows versus IEER

5-25Figure 5.6.10 15- ton Outdoor Coil Face Area * Number of Tube Rows versus IEER

Figure 5.6.11 30-ton Indoor Coil Face Area * Number of Tube Rows versus IEER

5-26Figure 5.6.12 30- to n Indoor Coil Face Area * Number of Tube Rows versus IEER

DOE developed equipment manufacturing costs for each physical/catalog teardown unit. Figure 5.6.13 through Figure 5.6.15 pr esent the manufacturing costs for the air -cooled CUACs with no heat or electric resistance heat with capacities of approximately 7.5 tons, 15 tons, and 30
tons. o

Figure 5.6.13 Manufacturing Cost for ~7.5- ton CUAC with Electric Resistance Heating or No Heating

o ~7.5 tons included 7.3 – 7.7 ton units, ~15 tons included 14.3 – 16.3 ton units , and ~30 tons included 27 – 30 ton units.

5-27Figure 5.6.14 Manufacturing Cost for ~15- ton CUAC with Electric Resistance Heating or No Heating

Figure 5.6.15 Manufacturing Cost for ~30- ton CUAC with Electric Resistance Heating or No Heating

The manufacturing cost model was used in subsequent analyses to determine the cost of small, large, and very large air -cooled CUAC designs incorporating series of design options to increase efficiency. The results of these analyses are discussed in section 5.6.6

.

5.6.4 Energy Modeling In the absence of industry-supplied data for each capacity or efficiency level, and because DOE was only able to conduct testing on a limited sample of equipment, DOE conduct ed energy modeling of the equipment obtained for reverse engineering analysis and of equipment designs

5-28that incorporate energy -saving design options. Moreover, the energy modeling analysis provided the energy consumption of individual components ( i.e. , compressor, indoor and outdoor fans,

an d controls) to characterize component energy use at different efficiency level s, which served as input to the building energy-use and end- use load characterization analysis (chapter 7) and the LCC and PBP analyses ( c hapter 8)

. DOE conducted energy modeling using the modeling tools developed by the Center for Environmental Energy Engineering (CEEE) of the University of Maryland at College Park (UMCP) . The modeling tools include a detailed heat exchanger modeling program CoilDesigner and a refrigeration cycl e modeling program VapCyc. A compressor database was also included in the refrigerant cycle modeling program. The refrigeration cycle modeling program integrates the compressor model, heat exchanger models and a built-in expansion model to complete a refri geration cycle model to simulate the performance of an air conditioning or heat pump system at specific operating conditions. Based on the key design features identified during physical equipment teardowns, DOE used the energy modeling tools to generate de tailed performance data ( e.g. , capacity and EER for all available capacity stages) and validated EER against the result obtained from laboratory testing at each IEER capacity level (25, 50, 75, and 100 percent). It should be noted that EERs at these capacity levels were calculated using interpolation or degradation, as prescribed in AHRI Standard 340/360–2007. With the validated energy models, DOE identified the key design features required for 7.5-ton, 15-ton, and 30-ton air -cooled CUAC units with electric resistance heating or no heating to achieve each efficiency level.

EER can be calculated through the modeling tools, but there is no direct output of IEER. The corresponding performance data at 100-percent, 75- percent , 50- percent , and 25- percent load leve ls were calculated separately, using interpolation and/or degradation adjustments from actual capacity stages as prescribed by AHRI Standard 340/360–2007, and then used these as input to calculate the IEER according to the equations set forth in the test standard. For part load conditions, iteration may be required depending on the configuration of the unit when the outdoor air temperature becomes a fu nction of the loading profile. In this case, multiple iterations were performed in VapCyc to ensure the outdoor temperature matches the requirement given the specific loading profile.

5.6.4.1 Heat Exchanger Model

Fin

- and

- tube heat exchangers are still commonly us ed for CUAC . Microchannel heat exchangers have been used for many years in the automotive industry due to their low weight and compact design. While challenges still exist for CUAC applications, there are products sold on the market that utilize microchann el heat exchangers for small, large, and very large capacity CUAC . Therefore, a heat exchanger model applicable for both fin

- and -tube and microchannel heat exchangers become necessary for this rulemaking.

The heat exchanger modeling tool CoilDesigner deve loped by CEEE at the University of Maryland College Park was employed for this rulemaking. This software program includes the modeling capability of a variety of heat exchangers: fin

- and -tube, microchannel, flat-tube, wirefin tube, and tube- in -tube heat e xchangers. Physical geometry parameters of the heat exchanger are needed as the input for modeling. For this rulemaking analysis , both fin

- and -tube and microchannel heat exchangers have been modeled. For fin

- and -tube heat exchangers, the

5-29geometry input par ameters include: number of tubes perpendicular to air flow, number of tube rows or banks parallel to air flow , tube length, tube outer diameter (OD), tube thickness, tube spacing perpendicular and parallel to air flow , fin type, fin pitch, and fin thicknes s. For microchannel heat exchangers, the geometry input parameters include: number of tubes perpendicular to air flow, tube length, tube height, tube width, tube vertical spacing, un-finned tube length, ports ( i.e. microchannels) per tube, port type, fin type, fin pitch, and fin thickness. Different heat exchanger parameters can be defined through the user interface of CoilDesigner. The circuitry of the heat exchangers can also be designed through the user interface to represent the actual connections of re frigerant tubes. Figure 5.6.16 shows the user interface of CoilDesigner.

The modeling approach of CoilDesigner is to divide each heat exchanger tube into multiple segments, and each segment is treated as a mini heat exchanger. Refrigerant -side and air

- side heat transfer and pressure drop calculations are performed in each segment of each tube. Users can define the number of segments needed to perform the calculation. In general, the accuracy of modeling results can be enhanced with a higher number of segments. However, the computation effort increases correspondingly, which essentially increases the modeling time. In this modeling wo rk, the number of segments of each tube is defined as 10 in order to provide reasonably accurate results, but without a significant increase in the computation time.

Figure 5.6.16 User Interface of CoilDesi gner

Inlet conditions of refrigerant- side and air

- side are needed as the input in order t o perform the heat exchanger modeling . These conditions include: refrigerant mass flow rate, inlet refrigerant temperature and pressure, air volume flow rate, inlet air pressure, temperature and humidity. O utlet conditions are calculated by the heat exchanger model. The output parameters Tube segment Circuitry

5-30include the refrigerant

- side and air

- side exit temperatures and pressures, and the heat exchanger capacities, etc. CoilDesigner also has a number of heat transfer and pressure drop correlations that may be se lected as shown in Table 5.6.4 . In this modeling work, the heat transfer and pressure drop correlations selected were those that provided the best match to the labora tory testing results

. The same correlations were used for units modeled at different capacities.

CoilDesigner can work as a standalone design tool for various types of heat exchangers, and it can also be integrated into a refrigeration cycle to perform cycle modeling. When CoilDesigner is integrated into a refrigeration cycle, no input on the refrigerant side parameters is needed because they are calculated internally as part of the refrigeration cycle modeling in VapCyc. In this case, only the input parameters from the air side are needed, which include the air pressure, volume flow rate, inlet air temperature and humidity for both the condenser and evaporator

.

5-31Table 5.6.4 Heat Transfer and Pressure Drop Correlations

Fin

- and -tube

Evaporator Air

- side Heat Transfer Refrigerant

- side Heat Transfer

Wang

- Hwang

- Lin 2 Two -phase Jung Radermacher 5 Vapor Gnielinski 4

Air

- side Pressure Drop Refrigerant

- side Pressure Drop

Wang

- Hwang

- Lin 2 Two -phase Jung Radermacher 6 Vapor Blasius 7

Fin

- and -tube

Condenser Air

- side Heat Transfer Refrigerant

- side Heat Transfer

Wang

- Hwang

- Lin 2 Liquid Gnielinski 4

Two

- phase Shah 8 Vapor Gnielinski 4

Air

- side Pressure Drop Refrigerant

- side Pressure Drop

Wang

- Hwang

- Lin 2 Liquid Blasius 7

Two

- phase Homogeneous 9 Vapor Blasius 7

Microchannel

Condenser Air

- side Heat Transfer Refrigerant

- side Heat Transfer

Chang- Wang 3 Liquid Gnielinski 4

Two

- phase Shah 8 Vapor Gnielinski 4

Air

- side Pressure Drop Refrigerant

- side Pressure Drop

Chang- Wang 3 Liquid Blasius 7

Two

- phase Chen Vapor Blasius 7

2 : Wang et al. (2002) 3 : Wang et al. (1999)

4 : Gnielinski (1976) 5 : Jung and Radermacher (1989a)

6 : Jung and Radermacher (1989b) 7 : Incorpera and DeWitt (1996)

8 : Shah (1979) 9 : Ould Didi et al. (2002)

5.6.4.2 Compressor Model The compressor model utilizes the AHRI 10- coefficient model [1] 10 , as described in Eq. 5.1 :

X = C1 +C2·S+C3·D+C4·S 2 +C5·S·D+C6·D 2 +C7·S 3 +C8·D·S 2 +C9·S·D 2 +C10·D 3 Eq. 5

. 1

where:

C = Equation coefficient, represents compressor performance S = Suction dew point temperature, degrees Celsius ( °C) D = Discharge dew point temperature, °C

5-32X represents any of the following variables:

• Power input, kW

• Mass flow rate, kg/s

• Current, A

• Compressor efficiency

The coefficients for each compressor can be obtained from compressor manufacturers. The cycle modeling program also provides a database that includes a comprehensive list of compressor coefficients

5.6.4.3 Expansion Model

VapCyc uses an isenthalpic expansion model. The subcooling and superheating are specified as inputs through the user interface of VapCyc. As equipment manufacturer s typically provide recommended ranges of subcooling and superheating to optimize system performance

, values within the recommended ranges were used in this modeling work. The refrigeration cycle solves automatically to meet the specific subcooling and superheating requirements.

5.6.4.4 Fan Model

Indoor and outdoor fan power consumption has a great impact on the IEER of a unit, particularly for high IEER units. In the case that a unit is tested in a laboratory, the indoor and outdoor fan power use is measured, and therefore, they are used directly for the EER and IEER calculation. If not tested, the fan power use is estimated from the manufacturer published performance data at the nominal air flow rate and minimum static pressure

. For a given refrigeration cycl e at full load condition, the fan power consumption can be calculated given the air flow rates and static pressure. In addition, as design options may include changes in heat exchanger designs and air flow , the fan power requirement also changes . In such

case s , the air -side pressure drop increases or decreases with the variation of air velocity due to coil size change. The air -side pressure drop variation is converted to fan power consumption change, which follows the fan power curve for the given specifications of equipment manufacturers.

Fan power consumption at part load conditions is estimated to be a function of the full load power consumption, as described in Eq. 5.2 . Typically, fan power consumption correlates to the cube of air flow rate s according to Fan Laws. The superscript of 3 was replaced with 2.5 to better characterize the fan power estimate of f

in -and-tube and microchannel heat exchangers

.

5-33P part load = P full load ∗ ( Airflow part load Airflow full load ) 2

. 5 Eq. 5.2

5.6.4.5 Refrigeration Cycle Model The cycle model utilizes the refrigeration cycle model VapCyc developed by CEEE at UMCP. The cycle model integrates the above-mentioned compressor model, heat exchanger models and expansion model to form a refrigeration cycle model. Figure 5.6.17 shows a screenshot of a refrigeration cycle from VapCyc using a dual -compressor configuration. VapCyc also provides the flexibility of various design options, including using multiple compres sors and heat exchangers in parallel. This feature provides great flexibility in modeling large and very large CUAC equipment, which often have multiple compressors and refrigeration cycles. In addition to the parameters describing the compressors and heat exchangers, system parameters such as degree of superheat and subcooling are also required as input for the modeling. Initial values of condensing and evaporating temperatures are also needed to initiate the iterations for solving the cycle. The modeling program has a built-in refrigerant property routine that provides the properties needed for the evaluation. The iteration terminates when the convergence criteria have been satisfied. The performance data are then output to an Excel spreadsheet for further analysis.

Figure 5.6.17 Schematic of a Refrigeration Cycle Using a Dual Compressor Configuration

5.6.5 Design Option Analysis
As discussed above, DOE selected 7.5 -ton, 15-ton and 30-ton unit designs to be representative of their equipment classes. Models were developed for the range of efficiency levels considered for each equipment class, from the baseline efficiency to the max

- tech efficiency, based on designs consistent with equipment that is sold on the market. The energy models at each capacity level were validated against laboratory testing and/or manufacturer data at multiple efficiency levels. In some cases the models were developed to represent designs of specific equipment models that are available for sale or that were tested and reverse

engineered —in other cases, the models represented modifications of these designs based on consideration of alternative design options.

5-345.6.5.1 7.5- ton Models

Five 7.5-ton units were purchased and tested according to AHRI Standard 340/360–2007. Among the five tested units, one unit was used to validate the model built in CoilDesigner and VapCyc. This air-conditioning unit has a nominal cooling capacity of 7.5 tons, and is rated at 11.2 EER and 11.4 IEER. It features a single refrigerant circuit with a single scroll compressor, fin

- and -tube indoor and outdoor heat exchangers. The compressor model number was identified during the tear down analysis after completing the performance testing in the laboratory. Indoor and outdoor heat exchanger specifications were collected for creating the coil models in CoilDesigner. The circuiting of both heat exchanger s in CoilDesigner also follows exactly the actual heat exchanger geometry

. Figure 5.6.18 shows the model validation results of the test ed 7.5-ton unit at 100- percent, 75-percent, 50- percent and 25- percent load conditions. The maximum deviation between the tested and modeling resu lts are 4.8 percent , with the modeling results slightly lower than the tested results. The overall tested IEER is 12.87, and the modeled IEER is 12.27, which is 4.7 percent lower than the tested IEER. The purpose of the model validation is to create models in CoilDesigner and VapCyc so that the models, with adjustment to parameters in CoilDesigner and VapCyc (e.g., heat transfer and pressure drop correlations, initial values, etc.), output performance data close to the actual tested data, and then used for design option analysis after validation. Therefore, all reported results were final outputs from CoilDesigner and VapCyc, and no further correction was made for the difference between modeled and tested results.

Figure 5.6.18 Model Validation for 7.5-Ton CUAC Units After Applying IEER Weighting Factors

The validated models were used for subsequent design option analysis. Table 5.6.5 shows the specifications of the different efficiency levels for the 7.5 -ton units. EL 1 and EL 2 are based on actual laboratory testing data, and the max -tech unit is based on the specificati ons of a unit available on the market with modeled IEER matched with published data. T he remaining the

5-35efficiency levels are based on modeling results. The baseline efficiency level features a single refrigerant circuit with a fixed speed scroll compressor

, fin

- and -tube condenser and evaporator. The air flow rates through the condenser and evaporator are also fixed.

The design change from the baseline efficiency level to EL1 is the increase of condenser and evaporator coils face area. Increased coil face area enhances the heat transfer in the condenser and evaporator. Given the same air flow rate, the increased coil face area leads to a lower velocity of air flowing through the coils. This reduces the air side pressure drop, which lowers the fan power consumption and contributes to an improvement of IEER.

The design improvement from EL 1 to EL 2 include the increase of condenser and evaporator coils face area, and also features a dual

- compressor design with two separate refrigerant circuits. The dual

- compressor design allows two stages of capacity at different load conditions. At the full load condition, both compressors are in operation to meet the capacity demand. While at part load conditions, only one compressor is operating, allowing the power saving whic h essentially enhances the IEER.

The main design improvement from EL 2 to EL 3 is the implementation of a variable speed indoor fan. The variable speed indoor fan provides the optimum air flow rates needed to maximize the performance while minimizing the f an power consumption. Two stages of air flows are also provided in the outdoor unit in order to minimize the fan power consumption at part load conditions.

For the max tech efficiency level ( i.e.
, EL 4), a single refrigerant circuit design is implemented to further improve IEER . The single refrigerant circuit design ensures the best utilization of heat exchanger heat transfer area during part load conditions, and therefore significantly enhances the overall system performance. The compressors were also selected with different capacities to deliver three stages of capacity: i.e. , full load capacity at 100 percent load conditions, compressor with greater capacity running at 75 percent load condition, and compressor with lower capacity running at 50 percent and 25 percent load conditions. Larger condenser and evaporator coils are also utilized for the max tech unit compared to other efficiency levels. A variable speed indoor fan provides different air flow rates depending on various load conditions. The condenser fans also provides three stages of air flows to effectively dissipate the condenser heat to the ambient environment while keeping the fan power consumption at a minimal value.

5-36Table 5.6.5 Design Options for 7.5-Ton CUAC U nits

ID Airflow OD Airflow

# Basis IEER Ref. Circuit # of Comp. Type Stage Capacity ratio Speed Type Face

area [ft^2] Fin pitch Rows Stage Type Fin pitch Face

area [ft^2] Row Stage

Baseline Modeling 11.4 1 circuit 1 Scroll 1 100 Fixed Tube-fin 7.2 15 3 1 Tube-fin 17 16.6 2 1

EL1 Teardown / Testing 12.9 1 circuit 1 Scroll 1 100 Fixed Tube-fin 8.9 15 3 1 Tube-fin 17 20.5 2 1

EL2 Teardown / Testing 14.0 2 circuits 2 Scroll 2 50/50 Fixed Tube-fin 11.1 15 4 1 Tube-fin 17 25.1 2 1

EL3 Modeling 14.8 2 circuits 2 Scroll 2 50/50 Fixed Tube-fin 11.1 15 4 VS Tube-fin 17 25.1 2 2

EL4 Modeling with Published Manuf. Data 19.9 1 circuit 2 Scroll 3 64/36 Fixed Tube-fin 17.5 15 4 VS Tube-fin 18 36.1 2 3 Efficiency Level Compressor Indoor Heat Exchanger Outdoor Heat Exchanger

5-375.6.5.2 15- ton Models Two 15-ton units were purchased and tested. One of the units was selected for validating the model in CoilDesigner and VapCyc in order to develop the design options for the 15-ton capacity level. This unit has a nominal cooling capacity of 15.0 tons, and is rated at 12.2 EER and 13.2 IEER. It features two separate refrigerant circuits with two scroll compressors, fin

- and

tube indoor and outdoor heat exchangers. The compressor model numbers were identified during the tear down analysis after completing the performance testing in the laboratory. Indoor and outdoor heat exchanger specifications we re collected for creating the coil models in CoilDesigner. The circuiting of both heat exchangers in CoilDesigner also follows exactly the actual heat exchanger geometry

Figure 5.6.19 shows the model validation of the test 15-ton unit at 100- percent , 75- percent , 50- percent and 25- percent load conditions. The maximum deviation between the tested and modeling results are 1.2 percent , with the modeling results slightly higher than the tested results. The overall tested IEER is 13.22, and the modeled IEER is 13.28, which is only 0.5 percent higher than the tested IEER. This shows a very close match between the tested and modeled results.

Figure 5.6.19 Model Validation for 15 -Ton CUAC Units After Applying IEER Weighting Factors

As a similar approach employed for the 7.5-ton units, the validated 15-ton models were used in the subsequent design option analysis. Table 5.6.6 shows the specifications of the different efficienc y levels for the 15 -ton units. EL 2 is based on actual laboratory testing data, and the max -tech unit is based on the specifications of a unit available on the market with modeled IEER matched with published data. A ll other efficiency levels are based on m odeling results.

Baseline efficiency level features a dual

- refrigerant -circuit with one fixed speed scroll compressor in each refrigerant circuit. Both the condenser and evaporator utilize fin

- and -tube

5-38type heat exchangers. Fixed speed indoor and outdoor fans provide constant air flow rates through the condenser and evaporator coils.

The design change from the baseline efficiency level to EL1 is the increase of condenser and evaporator coils face area. Increased coil face area enhances the heat transfer in the condenser and evaporator. Given the same air flow rate, the increased coil face area leads to lower velocity of air flowing through the coils. This reduces the air side pressure drop, which lowers the fan power consumption and contributes to the impro vement of IEER.

The design improvement from EL 1 to EL 2 includes the increase of condenser and evaporator coils face area, and the number of tube rows of the evaporator coil is also increased from 3 to 4. A more efficient indoor blower was also implemente d in EL 2, which lowers power consumption, and therefore leads to a higher IEER compared to EL 1.

The main design improvement from EL 2 to EL 3 is the implementation of a variable speed indoor fan. The variable speed indoor fan provides the optimum air flo w rates needed to maximize the performance while minimizing the fan power consumption. Two stages of air flows are also implemented in the outdoor unit in order to minimize the fan power consumption at part load conditions.

Similar to the max -tech unit of the 7.5-ton equipment class, a single refrigerant circuit design is implemented in the 15 -ton max tech unit. The single refrigerant circuit design ensures the best utilization of heat exchanger heat transfer area during part load conditions, and therefore significantly enhances the system performance. The compressors were also selected with different capacities to deliver three stages of capacity: i.e. , full load capacity at 100 percent load conditions, compressor with greater capacity running at 75 percent load condition, and compressor with lower capacity running at 50 percent and 25 percent load conditions. Larger condenser and evaporator coils are utilized for the max tech unit compared to other efficiency levels. A variable speed indoor fan provides different air flow rates depending on various load conditions. The condenser fans also prov ides three stages of air flows to effectively dissipate heat to the ambient environment while keeping the fan power consumption at a minimal value.

5-39Table 5.6.6 Design Option for 15-Ton CUAC U nits

ID Airflow OD Airflow

# Basis IEER Ref. Circuit # of Comp. Type Stage Capacity ratio Speed Type Face

area [ft^2] Fin pitch Rows Stage Type Fin pitch Face

area [ft^2] Row Stage

Baseline Modeling 11.2 2 circuits 2 Scroll 2 50/50 Fixed Tube-fin 16.2 15 3 1 Tube-fin 21 26.6 2 1

EL1 Modeling 12.2 2 circuits 2 Scroll 2 50/50 Fixed Tube-fin 24.5 15 3 1 Tube-fin 21 40.4 2 1

EL2 Testing 13.2 2 circuits 2 Scroll 2 50/50 Fixed Tube-fin 22.0 15 4 1 Tube-fin 17 42.8 2 1

EL3 Modeling 14.2 2 circuits 2 Scroll 2 55/45 Fixed Tube-fin 22.0 15 4 VS Tube-fin 17 42.8 2 2

EL4 Modeling with Published Manuf. Data 18.4 1 circuit 2 Scroll 3 64/36 Fixed Tube-fin 26.4 15 4 VS Tube-fin 18 59.2 2 3 Efficiency Level Compressor Indoor Heat Exchanger Outdoor Heat Exchanger

5-405.6.5.3 30- ton Models One 30-ton unit was purchased and tested. This unit has a nominal cooling capacity of 30 tons, and is rated with 10.1 EER and 11.9 IEER. It features two separate refrigerant circuits with two fixed speed scroll compressors in each circuit. It has fin

- and -tube indoor and outdoor heat exchangers. Because the indoor coil has four rows of tubes, it is designed to have a front-back split for the tw o refrigerant circuits to account for better part load performance. During the literature research of the 30 -ton units, it was found that most of the 30-ton units on the market feature microchannel condenser coils, and it was also identified that the teste d unit also has an alternative option with a microchannel condenser coil at identical performance rating. Therefore, the tested unit with a fin

- and -tube condenser coil was selected for validating the models in CoilDesigner and VapCyc as a first step , and then a microchannel condenser coil identified from the manufacturer specification sheet was employed to replace the fin

- and -tube condenser coil to revalidate the models in CoilDesigner and VapCyc in order to develop the design options for different 30 -ton capacity levels. The compressor model numbers were identified during the tear down analysis after completing the performance testing in the laboratory.

Figure 5.6.20 shows the model validation of the test 15-ton unit at 100- percent , 75- percent , 50- percent an d 25- percent load conditions. The maximum deviation b etween the modeling and tested results are 3.3 percent , with the modeling EER slightly higher than the tested result. The difference between modeling IEER and test result is found to be -2.3 percent.

Figure 5.6.20 Model Validation for 30-Ton CUAC U nits with T ube -F in C ondensers After Applying IEER Weighting Factors

As a second step of the model validation, the fin

- and -tube condenser was replaced with a microchannel condenser in order to be representative of the technologies implemented in the 30- ton units. The indoor coil remains the same as previously validated.

By utilizing the microchannel condenser coils, the model was revalidated , and the results are shown in Figure 5.6. 21 . The maximum deviation between the modeling and tested EER s are

-

5-412.8 percent , with the modeling results slightly lower than the tested results. The difference between the modeling and tested IEER is -1.7 percent , with the modeling result slightly lower than the tested value.

Figure 5.6.21 Model Validation for 30-Ton CUAC U nits with M icrochannel C ondensers After Applying IEER Weighting Factors

Based on these validation analyses, DOE believes the energy models for each capacity is representative of the actual unit performance.

T able 5.6.7 shows the specifications of the different efficiency levels for the 30 -ton units. A 30 -ton unit was tested and used for the model validation, as elaborate previously. Because the efficiency of this tested unit does not match precisely with the desired IEER level, it is not directly used in this design matrix. As a result, all efficiency levels of the 30 -ton units are based on modeling results.

Baseline efficiency level features a dual

- refrigerant

- circuit with two fixed speed scroll compressors in each refrigerant circuit. It also has fin

- and -tube evaporator and microchannel condenser coils. Fixed speed indoor and outdoor fans provide constant air flow rates through the condenser and evaporator.

The design change from the baseline efficiency level to EL1 includes the increase of condenser and evaporator coils face area, and the implementation of two stages of air flow in the condenser coils to reduce the condenser fan power consumption in part load conditions. Given the same air flow rate, the increased coil face area leads to lower velocity of air flowing through the coils. This reduces the air side pressure drop, which lowers the fan power consumption and contributes to the improv ement of IEER.

The design improvement from EL 1 to EL 2 include the increase of condenser face area, and the number of outdoor fans also increases from 2 to 4 with smaller motors in each fan assembly in order to minimize the condenser fan power consumption.

5-42The design improvement from EL 2 to EL 3 is the imp lementation of a variable speed indoor fan and increased number of compressor staging. The variable speed indoor fan provides the optimum air flow rates needed to maximize the performance while minimizing the fan power consumption. Increased compressor staging lowers the compressor power at part load conditions. Four stages of capacity provide refined performance, i.e. , four, three, two and one compressors are in operation for 100 percent, 75 percent, 50 percent and 25 percent load conditions, respectively.

Both the 7.5-ton and 15- ton max tech units feature a single refrigerant circuit to maximize the coil surface area use during part load conditions for maximizing IEER. However, such a feature is not applicable in a 30-ton unit max tech unit due to potentia lly challenges of oil circulation in large refrigeration systems. Therefore, the 30

- ton max tech unit features a dual

refrigerant circuit design. As noted above, the i ncreased compressor staging at the max

- tech level lowers the compressor power at part load conditions.

Condenser coil size was further increased from EL 3 in order to effectively dissipate condenser heat to the ambient in order to lower overall system power consumption. A variable speed indoor fan provides different air flow rates depending on various load conditions. The condenser fans also provides four stages of air flows to effectively dissipate heat to the ambient environment while keeping the fan power consumption at a minimal value.

Comparing to the max tech units of 7.5-ton and 15-ton units, the 30-ton max tech unit has a much lower IEER. As the capacity of a unit increases, the design of such a unit has to consider the physical size in order to account for convenience of delivery and installation. Therefore, instead of significantly increasing the size of the condenser and evaporator coils, the air flow rates through the condenser and evaporator are increased substantially. The increase of air flow rates results in high fan power consumption, which essentially lowers the limit of IEER th at a unit can reach. This is the main reason that the 30-ton max tech unit has an IEER much lower than that of the 7.5-ton and 15-ton units.

5-43Table 5.6.7 Design O ptions for 30 -Ton CUAC U nits

ID Airflow OD Airflow

# Basis IEER Ref. Circuit # of Comp. Type Stage Capacity ratio Speed Type Face

area [ft^2] Fin pitch Rows Stage Type Fin pitch Face

area [ft^2] Row Stage

Baseline Modeling 10.1 2 circuits 4 Scroll 2 25/25/ 25/25/ Fixed Tube-fin 21.9 15 4 1 Microchannel 23 23.0 1 1

EL1 Modeling 11.6 2 circuits 4 Scroll 2 25/25/ 25/25/ Fixed Tube-fin 31.3 15 4 1 Microchannel 23 32.9 1 2

EL2 Modeling 12.5 2 circuits 4 Scroll 2 25/25/ 25/25/ Fixed Tube-fin 31.3 15 4 1 Microchannel 23 46.1 1 2

EL3 Modeling 13.5 2 circuits 4 Scroll 4 25/25/ 25/25/ Fixed Tube-fin 31.3 15 4 VS Microchannel 23 46.1 1 2

EL4 Modeling with Published Manuf. Data 15.5 2 circuits 4 Scroll 4 25/25/ 25/25/ Fixed Tube-fin 31.6 15 4 VS Microchannel 23 68.4 1 4 Efficiency Level Compressor Indoor Heat Exchanger Outdoor Heat Exchanger

5-445.6.5.4 Design Option Summary

Table 5.6.8 summarizes the detailed design options for the baseline efficiency and incremental efficiency levels.

Detailed performance data at different load conditions for 7.5-ton, 15-ton and 30-ton units are shown in Figure 5.6.22

, Figure 5.6.23 and Figure 5.6.24 , respectively. It can be seen that the max -tech unit (EL 4) has significantly higher EERs than other efficiency levels due to the b est available technologies implemented ( e.g. , variable speed indoor blowers, staged outdoor air flows

, capacity staging, larger coils, and single refrigerant circuit (7.5-ton and 15-ton), etc. ). Moreover, the slope of EL 4 flattens out as capacity increases from 7.5 -ton to 15-ton, and to 30- ton. This is mainly due to the substantial increase of indoor and outdoor fan power, which takes a much higher percentage of the overall power consumption as the system capacity increases. Comparing 30-ton units to 15-ton and 7.5-ton units, physical size of the units do no increase proportionally to the increase of capacity. Larger fans are utilized to draw more air at a higher velocity flowing through the coils, which result in an increase of static pressure, and therefore a significant increase of fan power consumption. It can also be seen that a s the ambient temperature decrease s, EER increases with decreasing part load until 50 percent . The transition point is from 50- percent to 25- percent part load, where the EER decreases. This is due to the degradation coeffic ient applied at the last part load condition.

Figure 5.6.22 7.5- Ton EERs at Different Load Conditions for Five Efficiency Levels

5-45Table 5.6.8 Design Option Summary for Different Efficiency Levels Equipment Type Baseline EL 1 (TSL 1) EL 2 (TSL 2) EL 3 (TSL 3) EL 4 (TSL 4)

Small CUAC

, CUHP Single compressor (1 stage) , fixed indoor and outdoor air flow Baseline + increase d outdoor and indoor coil heat transfer

areas EL1 + Two
compressor stages
, increase d outdoor and indoor coil heat transfer areas EL 2 + variable air volume for indoor fan

, two stage s outdoor coil air flow EL3 + Single refrigerant circuit (3 compressor stages), increased outdoor and indoor coil heat transfer areas

, three compressor and outdoor coil air flow stages

Large CUAC

, CUHP Two

- compressor s (2 stages) , fixed indoor and outdoor air flow Baseline + increase d outdoor and indoor coil heat transfer

areas EL 1 + increase d outdoor and indoor coil heat transfer

areas EL 2 + variable air volume for indoor fan

, two stage s outdoor coil air flow EL 3 + Single refrigerant circuit (3 compressor stages), increase d outdoor and indoor coil heat transfer areas , three
compres sor and outdoor coil air flow stag es

Very Large CUAC, CUHP Four-compressors (2 stages)

, two refrigerant circuits, fixed indoor and outdoor coil air flow Baseline + increase d outdoor and indoor coil heat transfer

areas , two stages outdoor coil air flow EL 1 + increase d outdoor and indoor coil heat transfer

areas EL 2 + 4 compressor stages, variable air volume for indoor fan EL 3 + increase d outdoor and indoor coil heat transfer

areas , four stages outdoor coil air flow Note: In addition to the listed design options, most of the efficiency level steps included incremental indoor and outdoor fan and fan motor efficiency improvements.

5-46Figure 5.6.23 15-Ton EERs at D ifferent Load C onditions for F ive E fficiency L evels

Figure 5.6.24 30-Ton EERs at D ifferent Load C onditions for F ive E fficiency L evels Figure 5.6.25 and Figure 5.6.26 show the coil face area multiplied by the number of tube row for indoor and outdoor coils, respectively. T he progression of efficiency levels correlates with the increase of heat transfer are a. From Figure 5.6.26 it can be seen that the heat transfer area of the 30 -ton units is even smaller than that of the 15-ton and 30-ton units. This is due to the fact that 30-ton units utilize microchannel condenser coils, and therefore, the heat transfer area is significantly less than other capacity levels.

5-47Figure 5.6.25 Indoor C oil F ace A rea * T ube Row N umber

Figu re 5.6.26 Outdoor C oil F ace Area * T ube Row N umber

5.6.6 Cost

- Efficiency Results With the validated energy models, DOE expanded the modeling tasks with various system design options and identified the key design features (consistent with equipment available on the market) required for 7.5-ton, 15-ton, and 30-ton air -cooled CUAC units w ith electric resistance heating or no heating to achieve each efficiency level. DOE then used these design features developed by the energy modeling in conjunction with the manufacturing cost model to

5-48determine the incremental manufacturing and shipping costs for each efficiency level for 7.5 -ton, 15-ton and 30-ton units.

DOE developed the cost-efficiency results shown in Table 5.6.9 through Table 5.6.11 for each cooling capacity range. DOE notes that the incremental costs would be equivalent for each of the equipment classes within a give n cooling capacity range ( i.e.
, CUAC units with electric resistance heating or no heat, CUAC units with all other types of heating, CUHP units with electric resistance heating or no heat, CUHP units with all other types of heating).

Table 5.6.9 Small Air

- Cooled CUAC and CUHP Cost

- Efficiency Relationships

Efficiency Level Incremental Manufacturer Production Cost Incremental Shipping Cost Baseline

- - EL1 $ 115.93

- EL2 $ 583.47

- EL3 $ 788.88

- EL4 (Max

- Tech) $ 1,277.04 $102.86

Table 5.6.10 Large Air

- Cooled CUAC and CUHP Cost

- Efficiency Relationships

Efficiency Level Incremental Manufacturer Production Cost Incremental Shipping Cost Baseline

- - EL1 $ 419.16

- EL2 $ 792.76 $192.86
EL3 $ 1,236.98 $192.86 EL4 (Max

- Tech) $ 1,554.26 $192.86

Table 5.6.11 Very Large Air

- Cooled CUAC and CUHP Cost

- Efficiency Relationships

Efficiency Level Incremental Manufacturer Production Cost Incremental Shipping Cost Baseline

- - EL1 $ 542.65

- EL2 $ 1,296.41

- EL3 $1, 834.67

- EL4 (Max

- Tech) $ 2,753.32 $444.00

5-49REFERENCES

1 American Metals Market . Available online at http://www.amm.com/

. (Last accessed December 2012)

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3 C.C. Wang, C.J. Lee, C.T. Chang, S.P. Lin, Heat transfer and friction correlation for compact louvere d fin

- and -tube heat exchangers, International Journal of Heat and Mass Transfer 42 (1999) 1945-1956.

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7 F.P. Incropera and D.P. DeWitt, Introduction to heat transfer. (3rd edition), John Wiley & Sons, New York (1996).

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10 ANSI/AHRI Standard 540, 2004, Standard for performance rating of positive displacement refrigerant compressors and compressor unit.

5-50