5-i CHAPTER 5

. ENGINEERING ANALYSIS

TABLE OF CO NTENTS

5.1 INTRODUCTION

................................ ................................ ................................ ........... 5

- 1 5.2 PRODUCT CLASSES ANAL YZED

................................ ................................ .............. 5

- 2 5.3 EFFICIENCY LEVELS

................................ ................................ ................................ ... 5

- 2 5.3.1 Baseline Efficiency Levels

................................ ................................ .............................. 5

- 3 5.3.2 Incremental Efficiency Levels

................................ ................................ ......................... 5

- 3 5.4 METHODOLOGY OVERVIEW

................................ ................................ .................... 5

- 5 5.4.1 Manufacturer Interviews

................................ ................................ ................................ .. 5

- 5 5.4.2 Product Testing

................................ ................................ ................................ ................ 5

- 6 5.4.3 Product Teardowns

................................ ................................ ................................ .......... 5

- 7 5.4.3.1 Selection of Units

................................ ................................ ........................... 5

- 7 5.4.3.2 Generation of Bill of Materials

................................ ................................ ...... 5

- 7 5.4.3.3 Cost Structure of the Spreadsheet Models

................................ ..................... 5

- 8 5.4.3.4 Cost Model and Definitions

................................ ................................ ........... 5

- 9 5.4.3.5 Cost Model Assumptions

................................ ................................ ............. 5

- 10 5.5 ANALYSIS AND RESULTS

................................ ................................ ........................ 5

- 10 5.5.1 Manufacturer Interviews

................................ ................................ ................................ 5

- 10 5.5.1.1 Product Classes

................................ ................................ ............................ 5

- 11 5.5.1.2 Design Features of Current Baseline Products

................................ ............ 5

- 12 5.5.1.3 Potential Incremental Efficiency Levels

................................ ...................... 5

- 12 5.5.1.4 Design Options Required to Improve Efficie ncy

................................ ......... 5

- 12 5.5.1.5 Impact on Consumer Utility

................................ ................................ ......... 5

- 13 5.5.1.6 Installation and Repair Costs as a Function of Efficiency

........................... 5

- 13 5.5.2 Product Testing

................................ ................................ ................................ .............. 5

- 13 5.5.2.1 Product Selection

................................ ................................ ......................... 5

- 13 5.5.2.2 Test Approach and Results

................................ ................................ .......... 5

- 14 5.5.3 Product Teardowns

................................ ................................ ................................ ........ 5

- 15 5. 5.4 Modeled Performance

................................ ................................ ................................ .... 5

- 16 5.5.4.1 Air Flow Optimization

................................ ................................ ................. 5

- 16 5.5.4.2 Additional Component Improvements

................................ ......................... 5

- 19 5.5.4.3 Design Options Not Specifically Considered

................................ .............. 5

- 21 5.5.5 Combined Tested and Modeled Performance

................................ ................................ 5

- 22 5.5.6 Cost Estimates

................................ ................................ ................................ ................ 5

- 26

LIST OF TABLES

Table 5.3.2.1 Portable AC Efficiency Level Equation Coefficients

................................ ............ 5

- 5 Table 5.4.3.1 Major Manufacturing Processes

................................ ................................ ............ 5

- 9 Table 5.5.5.1 Portable AC Efficiency Level Equation Coefficients

................................ .......... 5

- 25 Table 5.5.6.1 Incremental Portable AC Manufacturer Production Costs

................................ .. 5

- 265-ii LIST OF FIGURE S

Figure 5.3.2.1 Efficiency Level Curves by Cooling Capacity

................................ ..................... 5

- 5 Figure 5.4.3.1 Manufacturing Cost Assessment Stages

................................ ............................... 5

- 8 Figure 5.5.2.1 Measured Cooling Capacity and EER c m ................................ ............................. 5

- 15 Figure 5.5.4.1 R

- 410A Compressor Performance Char acteristics

................................ ............. 5

- 20 Figure 5.5.5.1 Modeled Cooling Efficiency versus Cooling Capacity at Each Efficiency

Level by Unit

................................ ................................ ................................ ..... 5

- 23 Figure 5.5.5.2 Modeled Power Consumption versus Cooling Capacity at Each Efficiency

Level by Unit

................................ ................................ ................................ ..... 5

- 24 Figure 5.5.5.3 Linear Trends Between Power Consumption and Cooling Capacity by

Efficiency Level

................................ ................................ ................................ . 5

- 25 Figure 5.5.5.4 Efficiency Level Curves by Cooling Capacity

................................ ................... 5

- 265-1 CHAPTER 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

an alysis consists of estimating the energy consumption and costs of portable air conditioner s (AC) at various levels of increased efficiency

. This section provides an overview of the engineering analysis (section 5.1 ), discusses product classes (section 5.2 ), establishes baseline and incremental efficiency levels (section 5.3 ), explains the methodology used during data gathering ( section 5.4 ) and discusses the analysis and results (section 5.5 )

. The primary inputs to the engineering analysis are baseline information from the market and technology assessment ( c hapter 3 of th is preliminary technical support document ( TSD ) ) a nd technology options from the screening analysis ( c hapter 4 of this preliminary TSD )

. Additional inputs were determined through teardown analysis and manufacturer interviews

. The primary output of the engineering analysis is a cost

- efficiency curve

. In the subsequent markups analysis ( c hapter 6 of this preliminary TSD ), DOE determined customer ( i.e.
, product purchaser) prices by applying distribution markups, sales tax and contractor markups

. After applying these markups, the cost

- efficiency curve serve s as the input to the building energy

- use and end

- use load characterization ( c hapter 7 of this preliminary TSD )

, and the life

- cycle cost (LCC) and payback period (PBP) analyses ( c hapter 8 of this preliminary TSD )

. DOE typically structures its engineering analysis around one of three methodologies

. These are: (1) the design

- option approach, which calculates the incremental costs of adding specific design options to a baseline model; (2) the efficiency

- level approach, which calculates the relative costs of a chieving 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 involves a “bottom

- up” manufacturing cost assessment based on a detailed bill of materials (BOM) derived from teardowns of the product or equipment being analyzed

. Deciding which methodology to use for the eng ineering analysis depends on the covered product , the design options under study, and any historical data that DOE can draw on.5-2

DOE used a hybrid approach of the design

- option and reverse

- engineering approaches for this analysis . This approach involved p hysically disassembling commercially available products, reviewing publicly available cost information, and modeling equipment cost. From this information, DOE estimated the manufacturer production costs ( MPC s ) for a range of products currently available o n the market. DOE then considered the steps manufacturers would likely take to improve product efficiencies. In its analysis, DOE determined that manufacturers would likely rely on certain design option s to reach higher efficiencies. From this information, DOE estimate d the cost and efficiency impacts of incorporating specific design options at each efficiency level . This preliminary TSD chapter further describes the process DOE followed to establish its cost

- efficiency relationship for portable AC s

.

5.2 PRODU CT CLASSES ANALYZED
Because portable air condition er s are not currently covered by the Energy Policy and Conservation Act (ECPA) of 1975, Pub. L. 94

- 163 (42 United States Code (U.S.C.) 6291

– 6309)

, there are no existing product classes for these products. DOE may divide covered products into product classes by the type of energy used or by capacity or other performance

- related features that affect efficiency. Different energy conservation standards may apply to different product classes. (42 U.S.C. 6295(q))

DOE considered two product characteristics for potentially establishing multiple portable AC product classes: duct configuration and capacity. As discussed in chapter 3 of this preliminary TSD, DOE only conducted this preliminary analysis on single

- duct and dual

- duct portable ACs. DOE is not considering spot coolers in this analysis. Also a s discussed in chapter 3 of this preliminary TSD, duct configuration ( i.e. , the presence of a condenser inl et air duct from the unconditioned space) has an impact on portable AC efficiency; however, DOE is not aware of any unique consumer utility asso ciated with duct configuration. DOE determined that duct configuration, therefore, does not require separate pro duct classes.

Portable AC efficiencies also typically increase for products with higher capacities. From its test and modeled data, DOE observed a consistent trend relating efficiency to capacity across the range of analyzed capacities

. DOE relied on thi s trend to determine appropriate efficiencies for its analysis instead of separating portable AC s into different product classes by capacity. Therefore, for this preliminary analysis, DOE analyzed a single portable AC product class.

5.3 EFFICIENCY LEVELS

DOE d eveloped representative efficiency levels using a combination of test and modeled portable AC performance data

. Each efficiency level corresponds to a particular set of design options, primarily based on duct configuration.5-3

5.3.1 Baseline Efficiency Levels

Typically, a baseline unit is a unit that just meets current energy conservation standards and provides basic consumer utility. Because there are no existing energy conservation standards for portable AC s, DOE observed whether units tested with lower effic iencies incorporated similar design options or features , and considered these features when defining a baseline configuration

.
As discussed further in section 5.5.2

, based on testing conducted in support of DOE’s test procedure notice of proposed rulemaking ( NOPR ) issued on February 12

, 201 5 ( February 2015 Test procedure NOPR ), a and the notice of data availability (NODA) published in the Federal Register on May 9, 2014 (May 2014 NODA , 79 FR 26639 ), DOE observed that the air flow pattern through a portable AC has a significant effect on measured cooling capacity and cooling
energy efficiency ratio ( EER c m )

. Cooling capacity describes the net amount of heat the portable AC is able to remove from the conditioned space, in British thermal units per hour (Btu/h). EER c m is equal to the cooling capacity divided by the overall power draw of the unit while in cooling mode , in Btu per watt

- hour (Btu/Wh)

. For units that draw air from the conditioned space over the condenser and then exhaust it outside of the conditioned space, an equivalent amount of infiltration air must enter the conditioned space due to the net negative pressure differential that is created between the conditioned and unconditioned spaces . Because the proposed test conditions specify that infiltration air would be at a higher temperature than the conditioned air, the infiltration air offset s a portion or all of the cooling capacity for each portable AC

. The greater the amount of infiltration air, the lower the cooling capacity will be

.
Based on the measured condenser exhaust air flow rates and the corresponding calculated magnitude s of the infiltration air heating effect, DOE determined that single

- duct units ( i.e. , units that draw all of the condenser intake air from within the condit ioned space and exhaust to the unconditioned space via a duct) would represent the baseline efficiency level for portable AC s. Section 5.5.5 provides additional det ail on the EER c m - cooling capacity relationship DOE developed for the baseline efficiency level.

5.3.2 Incremental Efficiency Levels
DOE developed incremental efficiency levels based on the design options manufacturers would likely use to improve portable AC ef ficiency. As discussed in sections 5.3.1 and 5.5.2 , the presence of infi ltration air has a large impact on unit performance. DOE expects that when improving efficiencies beyond the single

- duct baseline, manufacturers would first make improvements to incrementally reduce the amount of infiltration air.

The first efficiency level beyond the baseline, E fficiency L evel 1, represents the first improvement a manufacturer would make for a single

- duct unit. This efficiency level assumes

a The test procedure is available at: http://www1.eere.energy.gov/buildings/appliance_standards/product.aspx/productid/79

.5-4

manufacturers would convert single

- duct units to dual

- duct, but that the un its would still have a significant quantity of infiltration air. A t E fficiency L evel 1 , infiltration air flow was selected to equal half of the total air flow over the condenser ( i.e. , half of the condenser air flow is from the conditioned space, and the o ther half is from the unconditioned space via the condenser inlet duct). This amount of infiltration air flow is approximately equal to the average observed for dual

- duct units in DOE’s test sample.

Efficiency L evel 2 re presents dual

- duct units with reduced infiltration air flow . Out of its test sample, DOE observed that all dual

- duct units drew in a certain amount of infiltration air. The best

- performing units in the test sample had infiltration air flow s equal to approximately 25 percent of the tota l condenser air flow . Units meeting E fficiency L evel 2 would have infiltration air flow s similar to the 25 percent observed in testing.

Efficiency L evel 3 represents ideal dual

- duct performance. At this level, the dual

- duct products would intake all of t he condenser air from the unconditioned space via the condenser inlet duct, resulting in no infiltration air. DOE notes that it did not observe this air flow configuration for any products in its test sample, but included it in this analysis because DOE
te ntatively concludes it is technically feasible and results in a significant increase in efficiency.

Efficiency L evel 4 is the max

- tech level as determined by DOE. This level combines the ideal dual

- duct air flow configuration described for E fficiency L ev el 3 with additional design option changes to improve efficiency. Although DOE did not observe any portable ACs with these additional design options, DOE regards each of them as options that manufacturers would be likely to consider incorporating to achiev e the highest possible efficiencies. At E fficiency L evel 4, units would incorporate more efficient compressors and blower motors , larger heat exchangers , and low

- standby

- power electronic controls . Similar to E fficiency L evel 3, DOE did not test any portable AC s performing at E fficiency L evel 4, but estimated the potential performance improvements for products incorporating these design changes based on available information and modeling described in section 5.5.4

. DOE relied on its investigative testing and modeled data to deter mine product EER c m and cooling capacity at each of the efficiency levels. These data resulted in a rang e of product efficiencies for each efficiency level depending on the individual product cooling capacities. DOE evaluated the relationships between cooling capacity and EER c m at each efficiency level configuration, and developed the following equation to d escribe the representative EER c m for a given cooling capacity at each efficiency level:

EER c m = Cooling Capacity

( A × Cooling Capacity + B )

Table 5.3.2

. 1 be low provides the coefficients A, in Wh/Btu, and B , in watts (W), for each analyzed efficiency level that would be used to determine EER c m in Btu/Wh

. Figure 5.3.2

. 1 plots each efficiency level curve for cooling capacities from 0 to 10,000 Btu/h.5-5

Table 5.3.2

. 1 Portable AC Efficiency Level Equation Coefficien ts Efficiency Level A Coefficient (Wh/Btu) B Coefficient (W) Baseline 0.113 855.5 EL1 0.1201 685.4 EL2 0.1222 566.3 EL3 0.1256 426.9 EL4 0.1205 355.1

Figure 5.3.2

. 1 Efficiency Level Curves by Cooling Capacity

Section 5.5.5 provides additional detail describing how DOE developed the relationships between EER c m and cooling cap acity at each efficiency level.

5.4 METHODOLOGY OVERVIEW

DOE relied on multiple source s of information for this engineering analysis

. These sources include manufacturer interviews, internal product testing, and product teardowns

.

5.4.1 Manufacturer Interviews

DOE understands that there is variability among manufacturers in product offerings

, design strategies , and cost structures

. To be tter understand and explain these variances, DOE5-6

conducted manufacturer interviews as part of this analysis

. These confidential int erviews provided a deeper understanding of the various combinations of technologies used to increase portable AC efficiency, and their associated manufacturing costs

. Sample questions for the engineering analysis that were sent to manufacturers participati ng in these interviews are contained in appendix 5

- A of this preliminary TSD.

5.4.2 Product Testing

DOE does not currently cover portable AC s and

, therefore

, does not compile a list of portable AC performance data. T here is also little publicly available data on portable AC performance from other sources . Where data is available, often the test basis is unknown or not directly applicable to this analysis ( e.g. , the C alifornia E nergy C ommission (CEC) requires reporting of spot coo ler performance based on American National Standards Institute (ANSI)/American Society of Heating, Refrigerating, and Air

- Conditioning Engineers (ASHRAE) Standard 128

- 2001 “Method of Rating Unitary Spot Air Conditioners ” (ANSI/ASHRAE 128

- 2001) ; however, mo re recent industry standards , including ANSI / Association of Home Appliance Manufacturers (AHAM) PAC

- 1

- 2009 “Portable Air Conditioners” b (AHAM PAC

- 1

- 2009)

, Canadian Standards Association (CSA) C370

- 2013 “Cooling Performance of Portable Air Conditioners ” ( CS A 370

- 13 ) c , and the 2011 updated version of ANSI/ASHRA E Standard 128 , ANSI/ASHRAE Standard 128

- 2011 “Method of Rating Unitary Spot Air Conditioners” (ANSI/ASHRAE Standard 128

- 2011 ) all require a substantially lower indoor ambient testing temperature).

To a ddress this lack of portable AC performance data, DOE conducted its own investigative testing . As discussed in the February 2015 Test Procedure NOPR, DOE conducted testing according to an air enthalpy method (similar to current industry test methods) and a calorimeter method (similar to the method used for room AC s). Specifically, DOE conducted the testing to:

 Investigate and determine the most representative test methodology for portable

ACs;

 Establish efficiency trends for product s over a range of capacities ;

 Develop a better understanding of the design options and product features currently available on the market;

 Develop a better understanding of the operational characteristics of portable AC s

.

b ANSI/AHAM test procedures are a vailable for purchase online at: www.aham.org

.

c CSA standards are available for purchase online at: http://shop.csa.ca/

.5-7

5.4.3 Product Teardowns

Other than obta ining detailed manufacturing costs directly from a manufacturer, the most accurate method for determining the production cost of a product is to disassemble representative unit s piece

- by

- piece and estimate the material

, labor , and overhead cost s associated with each component using a process commonly called a physical teardown. DOE performed physical teardown analysis on portable AC s from a range of manufacturers

. The teardown methodology is
exp lained in the following sections

.

5.4.3.1 Selection of Units

DOE generally adopt s the following criteria for selecting units for teardown analysis:

 T he selected products should span the full range of efficiency levels for each product class under consideration;

 W ithin each product class, the selected products should

, if possible, come from the same manufacturer and belong to the same product platform ;

 T he selected products should , if possible, come from manufacturer s with large market share s in that product class, although the highest efficiency products are chosen irres pective of manufacturer; and

 T he selected products should have non

- efficiency

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

5.4.3.2 Generation of Bill of Materials

The end resul t of each teardown is a structured BOM , which describe s each product 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 value

— added eq uipment needed ( e.g. , stamping presses, injection molding machines, spot

- welders, etc.) and the estimated cycle times associated with each conversion step

. The result is a thorough and explicit model of the production process.

Materials in the BOM are divided between raw materials that require conversion steps to be made ready for assembly, while purchased parts are typically delivered ready for installation. The classification into raw materials or purchased parts is based on DOE’s previous industry

ex perience, recent information in trade publications, and discussions with original equipment manufacturers (OEMs). For purchased parts, the purchase price is based on volume

- variable price quotations and detailed discussions with suppliers.

For parts fabri cated in

- house

, the prices of the underlying “raw” metals ( e.g. , tube, sheet metal) are estimated on the basis of 5

- year averages to smooth out spikes in demand . Other “raw” materials such as plastic resins, insulation materials, etc. are estimated on a cu rrent

- market5-8

basis. The cost s of raw materials are based on manufacturer interviews, quotes from suppliers, secondary research, and by subscriptions to publications including the American Metals Market d (AMM)

. Past price quotes are indexed using applicable Bureau of Labor Statistics producer price index tables as well as AMM monthly data

.

5.4.3.3 Cost Structure of the Spreadsheet Models

The manufacturing cost assessment methodology used is a detailed, component

- focused technique for rigorously calculating the manu facturing cost of a product (direct materials, direct labor and some overhead costs). Figure 5.4.3

. 1 shows the three major steps in generating the manufacturing cost.

Figure 5.4.3

. 1 Manufacturing Cost Assessment Stages

The first step in the manufacturing cost assessment was the creation of a complete and structured BOM from the disassembly of the units selected for teardown . The units were dismantled, and each part was 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 were based on industry experience, information in trade publications, and discussions with manufacturers. Interviews and plant visits were conducted with manufacturers to ensure accuracy on methodology and pricing.

Following the development of a detailed BOM, the major manufacturing processes were identified and developed for the spreadsheet model. Some of t hese processes are listed in Table 5.4.3

. 1

.

d For information on American Metals Market, please visit: www.amm.com

.5-9

Table 5.4.3

. 1 Major Manufacturing Processes
Fabrication Finishing Assembly/Joining Quality Control Fixturing Stamping/Pressing Brake Forming Cutting and Shearing Insulating Turret Punch Tube Forming Enameling Washing

Powder Coating De

- burring Polishing Refrigerant Charging Adhesive Bonding

Spot Welding Seam Welding Packaging Inspecting & Testing

Fabrication process cycle times for each part made in

- house were estimated and entered into the BOM. Based on estimated assembly and fabrication time requirements, the labor content of each appliance could be estimated. For this analysi s, DOE estimated labor costs based on typical annual wages and benefits of industry e mployees.

Cycle requirements for fabrication steps were similarly aggregated by fabrication machine type while accounting for dedicated vs. non

- dedicated machinery and/or change

- over times (die swaps in a press, for example). Once the cost estimate for each teardown unit was finalized, a detailed summary was prepared for relevant components, subas semblies and processes. The BOM thus details all aspects of unit costs : material, labor, and overhead.

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 entir ely from raw materials. Hybrid assemblies, consisting of purchased parts and parts made on site are thus also accommodated.

5.4.3.4 Cost Model and Definitions
The cost model is based on production activities and divides factory costs into the following categories :

 Materials: Purchased parts ( i.e.
, motors , valves

, etc .), raw materials, ( i.e. , cold rolled steel, copper tube, etc .), and indirect materials that are used for processing and fabrication.

 Labor: Fabrication, assembly, indirect, and supervisor labor. Fabr ication and assembly labor cost are burdened with benefits and supervisory costs.

 Overhead: Equipment, tooling, and building depreciation, as well as utilities, equipment and tooling maintenance, insurance, and property taxes.

Cost Definitions

Because there are many different accounting systems and methods to monitor costs, DOE defined the above terms as follows:5-10

 Direct material: Purchased parts (out

- sourced) plus manufactured parts (made in

- house from raw materials).

 Indirect material: Material used d uring manufacturing ( e.g. , welding rods, adhesives).

 Fabrication labor: Labor associated with in

- house piece manufacturing.

 Assembly labor: Labor associated with final assembly.

 Supervisory labor: Labor associated with fabrication and assembly basis. Assig ned on a span basis (x number of employees per supervisor) that depends on the industry.

 Indirect labor: Labor costs that scale with fabrication and assembly labor. These included the cost of technicians, manufacturing engineering support, stocking, etc . t hat are proportional to all other labor.

 Equipment depreciation: Money allocated to pay for initial equipment installation and replacement as the production equipment is amortized. All depreciation is assigned in a linear fashion and affected equipment li fe depends on the type of equipment

.

 Tooling depreciation: Cost for initial tooling (including non

- recurring engineering and debugging of the tools) and tooling replacement as it wears out or is rendered obsolete.

 Building depreciation: Money allocated to pay for the building space and the conveyors that feed and/or make up the assembly line.

 Utilities: Electricity, gas, telephones, etc.

 Maintenance: Annual money spent on maintaining tooling and equipment.

 Insurance: Appropriated as a function of unit cost.

 Property Tax: Appropriated as a function of unit cost.

5.4.3.5 Cost Model Assumptions
As discussed in the previous section, assumptions about manufacturer practices and cost structure played an important role in estimating the final product cost. In converting p hysical information about the product into cost information, DOE reconstructed manufacturing processes for each component using internal expertise and knowledge of the methods used by the industry. Site visits allowed DOE to confirm its cost model assumpti ons through direct observation of the manufacturing plant, as well as through manufacturer interviews, reviews of current Bureau of Labor Statistics data, etc

.

5.5 ANALYSIS AND RESULTS

5.5.1 Manufacturer Interviews

DOE conducted interviews with portable AC manufacturers to develop a better understanding of current product features and the technologies used to improve energy efficiency. The manufacturers interviewed represent a wide range of U

. S

. market share and included both domestic and international comp anies that sell portable AC s in the United States

. During these interviews, DOE asked manufacturers questions about the following topics related to the engineering analysis :5-11  Product classes

 Design features of current baseline products

 Proposed incremental efficiency levels

 Design options required to meet each efficiency level

 Performance at reduced ambient temperatures

 Impacts on consumer utility

 Installation and repair costs as a function of efficiency

The discussion helped DOE understand what proposed des ign options have already been implemented and what additional design options DOE should consider.

The discussion below represents a consolidation of the manufacturer responses.

5.5.1.1 Product Classes

Because DOE does not currently cover portable AC s, there are no existing product class divisions within this product type

. During m anufacturer interviews, DOE requested feedback on potential product classes that would separate single

- duct and dual

- duct units each into multiple product classes based on capacity

, from less than 8,000 Btu/h to greater than 14,000 Btu/h

. DOE established the potential capacity bins for product classes based on t he range of available capacities listed in publicly available data . DOE notes that these capacities correspond to existing indust ry test methods, and would not be comparable to cooling capacities as determined according to the method proposed in the February 2015 Test Procedure NOPR.

Manufacturers generally responded in support of product classes that separate single

- duct and dual

- duct configurations for testing and standards. They indicated that each configuration would have differen t efficiencies due to differing air conditions flowing over the condenser and other design choices impacting portability and nois e.

However, manufacturers s tate d that there is no significant consumer utility associated with a single

- duct configuration compared with a dual

- duct configuration. Manufacturers indicated that dual

- duct and single

- duct portable AC s of similar rated capaci ties typically have the same overall power, utilizing similar compressors, chassis sizes and fan speeds.

While there may be no utility associated with the different product configurations, manufacturer s indicated that single

- duct units tend to be more po pular due to a lower cost than the dual

- duct configuration and because they were the first configuration introduced to the market. Also, two ducts take up more space and can be cumbersome for consumers who are unfamiliar with the installation and presence of multiple ducts. However, manufacturer s also indicated that single

- duct units may have higher rates of returns due to consumer dissatisfaction with their cooling performance

.

M anufacturer s also indicated that the listed product classes, which were in 2,000 Btu/h intervals, may be too granular, and the re should be fewer capacity bins for each duct configuration

. DOE also received feedback that it should align product classes with room ACs so5-12

there is a direct compa rison between the two similar products. This would be helpful to consumers who make purchasing decisions based on capacity rather than efficiency rating.

5.5.1.2 Design F eatures of C urrent B aseline P roducts

DOE discussed with m anufacturers the features of baseline products. Because of the lack of a consistent test method, manufacturers indicated that it is difficult to compare efficiencies and capacities between products from different manufacturers

. However, m anufacturers indicated that baseline portable AC s typic ally include the same components as units at higher efficiencies, perhaps with smaller heat exchangers or less efficient compressors.

5.5.1.3 Potential Incremental Efficiency Levels

DOE asked manufacturers to comment on suitable efficiency levels for the potential portable AC product classes. Manufacturers were asked to comment on the appropriateness of each incremental efficiency level and the max

- tech levels. DOE based the incremental efficiency levels in the interview guide on publicly available efficiency and c apacity information. Accordingly, the efficiency levels do no t correspond to efficiencies that would be measured by the method proposed in the February 2015 Test Procedure NOPR. However, the information provided by manufacturers helped DOE understand the range of efficiencies that may be achieved as measured according to existing industry test methods.

In general, manufacturers did not object to the efficiency levels DOE selected for analysis ; however, there was some concern that larger increments in e fficiency between levels could be difficult to achieve

. Additionally, manufacturers expressed concern that not all products are currently rated using the same test method. Accordingly, certain efficiency levels may be too high or low depending on the ratin g conditions. Also, s ome manufacturers were concerned about meeting the maximum efficiency levels with current materials and components. T hey suggest ed that higher efficiency products are currently being investigated

, but the necessary changes are not
comp letely understood at this time.

5.5.1.4 Design O ptions R equired to Improve Efficiency

DOE asked manufacturers to describe the changes associated with each efficiency level relative to the baseli ne units in each product class. From the reverse

- engineering analysis and experience with room ACs and dehumidifiers , DOE predicted the key design options would be increased compressor efficiency and heat exchanger size s . DOE highlighted these options during discussions with manufacturers to determine the necessary design options to meet incremental efficiency levels

. Manufacturers generally agreed that the primary changes required to me e t higher efficiency levels are likely more efficient compressors and motors. They indicated that larger heat exchangers and higher air flow rates with larger ducting components would increase efficiency, but size and noise limitations associated with portability would limit the extent of5-13

these design options. Manufacturers also stated that the costs associated with these design options would be significant. Manufacturers confirmed that microchannel heat exchangers, variable

- speed compressors, and other advanced technologies to improve efficiency are not currently being implemented in portable ACs . Manufacturers stated that they would likely utilize improved compressor efficiencies and larger heat exchangers to improve portable AC efficiencies before incorporating these design options

.

5.5.1.5 Impact on Consumer Utility

DOE asked manufacturers how these design option changes may impact consumer utility. Manufacturers indicated that overall performance would not be impacted; however, larger fans
may increase the fan operating noise, and larger co mponents and cases would increase the overall unit weight and decrease portability

. Also, in addition to the general cost of parts associated with the design options, increasing the number of ducts would increase the packaging size , adding to the s hipping cost.

5.5.1.6 Installation and Repair Costs as a Function of Efficiency

M anufacturers indicated that s ingle

- duct units ar e more portable than dual

- duct units , and

are therefore e asier to install and move from one room to another. Otherwise, m anufacturers did
not indicate that product lifetime s or installation and repair costs would vary significantly with improvements in efficiency.

5.5.2 Product Testing

DOE conducted investigative testing on portable AC s in support of the May 2014 NODA and February 2015 Test Proced ure NOPR to determine the appropriate methodology to be included in a future DOE portable AC test procedure. 29 FR 26639 (May 9

, 2014) . DOE utilized the results of th is investigative testing to support th is preliminary engineering analysis. The following sections detail the testing process, from product selection through data analysis.

5.5.2.1 Product Selection

DOE ’s test sample included 2 4 portable AC s. DOE selected units covering a range of manufacturer

- rated capacities (5,000 to 14,000 Btu/h) and ene rgy efficiency ratios ( EERs

, 7.0 to 12 Btu/ Wh ) from a range of manufacturers. Because DOE does not currently regulate portable AC s, the rated capacities and EERs do not necessarily reflect performance under the conditions proposed in the February 2015 Test Procedure NOPR; however, they provided a basis for DOE to differentiate between units available on the market. DOE’s test sample also covered the two major product configurations: 17 single

- duct units and 7 dual

- duct units. DOE notes that one of the d ual

- duct units shipped with a conversion kit to enable testing in single

- duct configuration. DOE tested this unit in both single

- duct and dual

- duct configurations.5-14 5.5.2.2 Test Approach and Results
DOE first performed testing in accordance with AHAM PAC

- 1

- 20 09 to determine baseline performance according to industry standards. This baseline performance was then used
to evaluate the suitability of the current industry standards through comparisons with modified or alternate test approaches.

As discussed and presented in the May 2014 NODA, DOE further investigated heat transfer effects not currently captured in available portable AC test procedures, through additional testing according to a room calorimeter approach adapted from ANSI/ASHRAE St andard 16

- 1983 (RA 99), “Method of Testing for Rating Room Air Conditioners and Packaged Terminal Air Conditioners” ( ANSI/ASHRAE Standard 16

- 1983 )

. DOE conducted that testing on a representative sample of four single

- duct and two dual

- duct units. For this preliminary analysis, DOE conducted similar calorimeter testing on an additional 18 test units not covered by the May 2014 NODA. The calorimeter testing used two test chambers

, one maintained at the indoor conditions , 80 degrees Fahrenheit (°F) dry

- bulb te mperature and 6 7  F wet

- bulb temperature

, and the other maintained at the outdoor conditions , 95  F dry

- bulb temperature and 75  F wet

bulb temperature , specified in AHAM PAC

- 1

- 2009 . Rather than installing the test unit in the wall between the indoor and o utdoor test rooms, as for a room AC , the portable AC under test was located within the indoor test room with the condenser duct(s) interfacing with the outdoor
test room by means of the manufacturer

- supplied or manufacturer

- recommended mounting fixture

. DOE then considered a modified test approach that followed the procedure outlined in AHAM PAC

- 1

- 20 09 , but included calculations to account for any heat effect due to infiltration air

. DOE found that infiltration air heat input cause d a significant reductio n in cooling capacity and efficiency when compared with the results from the nominal AHAM PAC

- 1

- 2009 test procedure.

In the February 2015 Test Procedure NOPR

, DOE concluded that the AHAM PAC

- 1 test approach should be the basis of a DOE test procedure for portable AC s to ensure representative test results , minimize additional test burden, and align with current industry practices. Therefore

, DOE proposed referencing the new ly

- released version of the PAC

- 1 standard, AHAM PAC

- 1

- 2014 e with additional prov isions and clarifications to determine representative performance. Figure 5.5.2

. 1 pre sents the measured cooling capacity and EER c m of its test sample consistent with the approach proposed in the February 2015 Test Procedure NOPR. As can be seen from the lower measured cooling capacit ies compared to the manufacturer

- rated values, the inclusion of infiltration air heat ing results in a significant reduction in net cooling.

e As noted in the February 2015 Test Procedure NOPR, DOE’s testing and analysis in support of the test procedure rulemaking was completed prior to the publication of AHAM PAC

- 1

- 2014. After careful examinat ion, DOE concluded that the differences between the 2009 and 2014 versions of the test standard would not significantly affect testing results, and, therefore, DOE proposed a test procedure that would reference certain provisions of the current version of the standard (AHAM PAC

- 1

- 2014).5-15 Figure 5.5.2

. 1 Measured Cooling Capacity and EER c m

I n the February 2015 Test Procedure NOPR, DOE also proposed test procedures to determine heating capacity and efficiency in heating mode, energy consumption in off

- cycle mode, and energy consumption in various standby modes and off mode. In addition, DOE also proposed an overall combined EER ( CEER )

, which combines unit performance in each of these available modes

. However, b ecause cooling is the primary function of DOE expects that manufacturers would likely focus on improv ing efficiency in this mode to achieve higher CEERs. Accordingly, DOE focused on performance in cooling mode for this engineering analysis. Later rulemaking stages would consider portable AC performance based on CEER.

As detailed in the following sections, DOE utilized test data when conducting teardowns and modeling to correlate efficiency gains with certain design options for the units in the test sample.

5.5.3 Product Teardown s

After completing the investigative testing described in the pr evious section, DOE conducted teardowns on 23 units in its sample that were available at the end of the test series

. The teardown units spanned the range of product efficiencies and features available on the market from multiple manufacturers. DOE relied o n the portable AC teardowns to supplement the information gained through manufacturer interviews and to investigate how product construction related to performance observed during testing. Specifically, the teardowns allowed DOE to identify design features for improving efficiency and to develop corresponding manufacturing costs for products at different efficiency levels.

DOE observed all portable AC s in the teardown sample had similar construction. All units were housed in a plastic case with either a plastic or metal internal structure. The units5-16

typically featured distinct upper and lower internal sections to separate the evaporator and condenser and their associated components. The top section included the evaporator, evaporator blower, and filter, while the bottom section included the condenser, compressor, and condenser blower assembly, including a n air filter. For the single

- duct units, the duct was connected at one end to the condenser exhaust port on the back of the case and at the other end to the window mounting bracket for exhausting the air outside of the conditioned space

. Dual

- duct units similarly attached the duct to the back of the case at the condenser exhaust, but also included a second duct attached at the condenser air inlet. Both duc ts were connected to the window mounting bracket. For all units, t he accordion

- style collapsible plastic coil ducts were almost identical, with slight variations in diameter and construction ( i.e.
, some ducts included a wire support while others were entir ely plastic).

The units were constructed such that a ny condensate formed o n the evaporator in the upper chamber would drip over the condenser , allowing some or all condensate to evaporate before the remainder is collected in a small internal reservoir at the bottom of the unit . All units either implemented a slinger wheel or pump in the internal reservoir t o circulate any collected condensate back on to the condenser where it w ould be evaporated and removed from the case in the condenser exhaust air strea m. All units included a condensate drain outlet to allow manual draining of any condensate collected in the internal reservoir that exceed s the amount that could be re

- evaporated

. All units featured rotary R

- 410A compressor s secured to the base of the unit’s internal case platform . DOE observed that all blowers used permanent split capacitor (PSC) motors. The evaporator and condenser within each unit had similar dimensions and number of tube passes, and were connected via capillary tubes. The copper tub ing exiting the evaporator and entering the compressor was typically insulated, though the thickness and length of insulation varied among units. All of the units in DOE’s test and teardown sample featured electronic controls, although DOE believes other units available on the market may use electromechanical controls.

5.5.4 Model ed Performance
Although DOE tested and tore down a large sample of units from different manufacturers at varying capacities and efficiencies, the sample did not cover the entire range of efficiency levels and design options that are technically feasible

. To fill in the gaps in the teardown sample and to estimate the maximum efficiencies possible as measured by the method proposed in the February 2015 Test Procedure NOPR, DOE numeric ally modeled unit performance with various design option configurations

.

5.5.4.1 Air Flow Optimization
DOE’s test and teardown sample included both single

- duct and dual

- duct units covering a range of rated capacities and efficiencies . As discussed in the February 2015 Test Procedure NOP R, DOE determined that infiltration air has the most significant impact on performance when compared with other heat transfer components. DOE also found that air infiltration has the5-17

largest impact on single

- duct unit perfor mance, d ue to infiltration air flow equaling condenser inlet flow rates. Accordingly, single

- duct units typically had lower measured efficiencies and capacities compared to dual

- duct units. Therefore , DOE considered single

- duct units as the
current b aselin e configuration

. DOE expects that manufacture r s would rely on adjust ing the air flow configuration to improve the performance of units that produce significant infiltration air flow. DOE identified this as t he least expensive design option available to i ncrease both cooling capacity and efficiency , and therefore the most likely to be implemented . Other design options to improve efficiency ( e.g

. , increasing heat exchanger size or improving compressor and motor efficienc ies ) h ave smaller impact s on perform ance at higher costs . Therefore, DOE first considered incremental improvements to the air flow configuration to estimate the feasible improvements in efficiency for all units in the test and teardown sample.

E fficiency L evel 1

The first incremental change in the air flow design corresponds to E fficiency L evel 1. This change involves moving to a dual

- duct configuration t hat draws 50 percent of the condenser inlet from the conditioned space, and in turn, has an equivalent amount of infiltration air . DO E notes that dual

- duct units in its test sample drew between 37 and 72 percent of condenser inlet air from the conditioned space. This first incremental improvement represents a n improvement to an average performing dual

- duct unit currently available on th e market.

To determine the resulting impact on efficiency and capacity , DOE first reduced the infiltration air latent and sensible heat contribution by 50 percent

. The method proposed in the February 2015 Test Procedure NOPR determines the infiltrat ion air heating effect via a direct calculation, so DOE was able to account for this change with no additional modeling

. However, changing the condenser air source and internal air flow pattern leading to the condenser has additional effects on unit per formance beyond reducing infiltration air flow. While a single

- duct unit draws all condenser inlet air from the conditioned space, a dual duct unit with 50 percent infiltration air draws half of the condenser inlet air from the conditioned space and the
ot her half from the outdoor conditions. As a result, the average condenser inlet air conditions change from 80 °F dry

- bulb temperature and 51

- percent relative humidity to 87.5 °F dry

- bulb temperature and 45.5

- percent relative humidity (the average of the indoor and outdoor test conditions)

. T h e increase in dry

- bulb temperature and reduction in relative humidity result in less effective heat transfer from the condenser to the air stream

, decreas ing cooling capacity and efficiency.

To calculate the impact of the updated condenser air flow conditions on cooling capacity and efficiency , DOE performed energy modeling utilizing the MarkN program developed for use in its most recent room AC energy conservation standard s direct final rule. 7 6 FR 22454 (Apr. 21, 2011). The MarkN program was itself an update of an adaptation to the Oak Ridge National Laboratory Mark III Heat Pump program for modeling room AC cooling performance. This program was originally used in support of the 1997 room AC fi nal rule. 62 FR 50122 (Sept. 24,5-18

1997). The 1997 final rule and 2011 TSD f provide further details regarding the use of these programs in support of the room AC energy conservation standards rulemakings.

DOE first used the numerical model to simulate uni t performance for models in the test and teardown sample. The model inputs include product component specifications and the ambient operating conditions. DOE obtained component information from the product teardowns, including heat exchanger construction ( number of rows, tube passes, tube spacing, fin spacing, etc .), refrigerant tubing (lengths and diameters of inlet/outlet tubes and capillary tubes), and compressor specifications.

DOE calibrated the model results for multiple units in the teardown sample using available test data. DOE then modeled additional scenarios, changing only the condenser inlet air conditions. DOE developed a relationship between the condenser inlet air conditions and the resulting cooling capacity based on these simulations. This relationship was used to estimate the reduction in overall cooling capacity when condenser inlet conditions were adjusted for a combina tion of indoor and outdoor air.

DOE also used the MarkN model results to estimate the change in compressor power at the adjusted condenser inlet air conditions. C ompressor s draw more power at higher condenser inlet air temperature s because of the higher operating temperature and pressure of the refrigerant in the condenser

. DOE used the model results to develop a relations hip for compressor power consumption base d on condenser inlet conditions. The calculated efficiency results at each efficiency level account for the changes in compressor power draw at the different condenser inlet air conditions.

In addition to variations in compressor power draw , DOE also considered the increase in blower motor power required when moving from a single

- duct to dual

- duct configuration. DOE assumed that introducing an additional duct would require a 10

- percent increase in blower motor
power to overcome the added external static pressure associated with the additional duct.

Efficiency Levels 2 and 3

E fficiency L evel s 2 and 3 also represent dual

- duct performance, but with incrementally less condenser inlet air drawn from within the conditioned space. Efficiency L evel 2 represents 25

- percent condenser inlet air from the conditioned space, and E fficiency L evel 3 assumes that no condenser inlet air is drawn from the conditioned space. At E fficiency L evel 3 , there would be no pressure differential between the indoor and outdoor space s, resulting in no infiltration air. At these efficiency levels, DOE considered the same impacts on performance as for E fficiency L evel 1: air infiltration heat, compressor powe r, and blower motor power . However, DOE also

f The TSD in support of the 2011 room AC direct final rule is available online at: www.regulations.gov/#!documentDetail;D=EE RE

- 2007

- BT

- STD

- 0010

- 0053

.5-19

assumed that blower motor power would i ncrease by 5 percent at these efficiency levels to

a ccommodate the additional air flow through the condenser inlet duct.

5.5.4.2 Additional Component Improvements

As discussed ab ove, DOE also identified other design options that could be utilized to increase portable AC efficiency beyond improving the air flow configuration , including increas ing heat exchanger area and improv ing com pressor and fan motor efficiencies . DOE incorpora ted these changes to estimate performance at the max

- tech E fficiency L evel 4.

Increased Heat Exchanger Area

DOE is aware that increasing the heat transfer area of the evaporator and condenser coils may improve portable AC performance. At the max

- tech efficiency level, DOE considered the efficiency improvements that would be associated with larger coils. From manufacturer interviews, DOE learned that portable AC case sizes and weights are already approaching the limits of acceptable portability for cons umers. Significantly larger case sizes or greater weights would limit the ability for consumers to move units from room to room or to carry the unit up or down stairs. Accordingly, DOE considered a 10

- percent increase in coil cross

- sectional area in estima ting the potential efficiency improvemen t associated with larger coils. At this coil size, product cases and weights would not change significantly from those currently available on the market. Based on manufacturer interviews, DOE expects that manufacture rs would increase coil

cross

- sectional area to improve heat transfer rather than increasing heat exchanger depth or increasing fin density because it results in a relatively larger efficiency improvement.

To estimate the effect of larger heat exchangers on efficiency, DOE again modeled unit performance using the MarkN model. DOE began with the model inputs for the optimized dual

duct configuration ( i.e. , condenser inlet air at the outdoor conditions) and adjusted the heat exchanger parameters for a 10

- per cent larger cross

- sectional heat transfer area. DOE also modeled the other potential heat exchanger design options, increasing coil depth and increasing fin density, and confirmed that increasing cross

- sectional area resulted in the largest efficiency gain s.
Improved Compressor Efficiency

To determine appropriate ranges of compressor efficiencies, DOE utilized information gathered in the preliminary engineering analysis for dehumidifiers. g 79 FR 29380 (May 22, 2014)

. As shown in Figure 5.5.4

. 1 , compressors are available at rated EERs ranging from roughly 8.5 to 10.5 Btu/W h . DOE notes that this range represents a limited number of compressors based on a survey of the m arket, not necessarily those observed during teardowns.

g The preliminary engineering analysis for dehumidifiers is available in the preliminary TSD for this rulemaking, found at http://www. regulations.gov/#!documentDetail;D=EERE

- 2012

- BT

- STD

- 0027

- 0015

.5-20

DOE expects the range presented in Figure 5.5.4

. 1 to be representative of compressors available
to portable AC manufacturers.

Figure 5.5.4

. 1 R

- 410A Compressor Performance Characteristics

A t E fficiency L evel 4, DOE assumed the compressor in each optimized dual

- duct unit at E fficiency L evel 3 would be replaced with a compressor at an EER of 10.5 Btu/Wh

. The efficiency improvement associated with this design change varied from unit to unit dep ending on the efficiency of the compressor currently used. The overall average compressor efficiency observed for units in DOE’s teardown sample, and therefore the average compressor efficiency at Efficiency Level 3, was 9.8 Btu/Wh.

Improved Blower Motor Efficiency

DOE is aware that efficiency gains may be possible through improvements to the portable AC blower motor. DOE noted that all units in its teardown sample used PSC fan motors. Permanent

- magnet motors would provide slightly higher motor efficienc ies compared to PSC
motors ( DOE estimates them to be 80

- percent efficient compared to 60 percent for PSC motors)

, but the improvements to overall efficiency would be relatively small due to the smaller portion of energy consumed by the blower motor compared to the compressor. In interviews with DOE, manufacturers stated that they likely would not rely on changes to the blower to improve product efficiency due to the small efficiency gains and high cost. However, to consider the maximum efficiency possible for portable ACs, DOE considered this change to the blower motor

.

Low

- Standby

- Power Electronic Controls5-21

For th is preliminary engineering analysis, DOE considered portable AC performance in terms of EER c m and cooling capacity. In the February 2015 Test Procedure NOPR, DOE proposed a n overall CEER that would also incorporate energy consumption in other modes, su ch as heating mode, standby mode, off mode, and off

- cycle mode. DOE conducted this preliminary analysis only based on EER c m , which does not account for operation outside of cooling mode. However

, DOE still incorporated a change to low

- standby

- power electronic controls at the max

tech efficiency level because the downstream analyses for this preliminary analysis account for performance in the other non

- cooling modes.

5.5.4.3 Design Options Not Specifically Considered
DOE observed that manufacturers typicall y implement the design options discussed above to improve portable AC capacity and efficiency. Additionally, while many of the technology options identified in chapter 3 of this preliminary TSD may produce energy savings in certain real

- world situations, D OE did not further consider them in this analysis because there was not sufficient information available on the specific efficiency gains or the DOE test procedure would not capture those potential improvements. DOE considered the following design options in this engineering analysis, but does not expect manufacturers to rely on these features to meet higher efficiency levels.

Add Subcooler to Condenser Coil

DOE is aware that subcooling the refrigerant exiting the condenser may improve product efficiencies by increasing the amount of heat rejected by the condenser. However, based on product testing, DOE expects that any beneficial refrigerant subcooling already occurs within existing condensers. DOE observed that refrigerant temperatures exiting the condens er were well below the refrigerant condensing temperature. DOE expects that the use of condensate spray on the condenser contributes to the subcooling without the need for an additional heat exchanger.

Increase d Heat

- Transfer Coefficients
In the market a nd technology assessment, chapter 3 of this preliminary TSD, DOE identified technologies that would improve heat transfer coefficients in portable AC heat exchangers. In its teardown sample, DOE observed that units already incorporate many of the design op tions that would improve heat transfer coefficients, such as slit fins, grooved refrigerant tubes, and condensate spray over the condenser. DOE also identified microchannel heat exchangers as a potential means to improve heat

- transfer coefficients. As disc ussed in chapter 3, DOE expects the efficiency gains to be limited with a microchannel heat exchanger, but they may reduce the necessary refrigerant charge and condenser size.

Because portable ACs already include many design options to improve heat trans fer in the evaporator and condenser, and because it lacks information on the potential efficiency gains with microchannel heat exchangers, DOE did not specifically consider these design options in further improving portable AC efficiencies.

Improved Duct Connections5-22

In the market and technology assessment, DOE identified improved duct connections to the portable AC case and mounting bracket as a technology option to potentially improve portable AC performance by reducing air leakage . DOE did not observe any units in the test sample that provided additional sealing in the duct connections. DOE also lacks information regarding leakage rates and potential savings associated with reducing condenser air leakage to the room. Therefore, DOE did not further consi der the improvements associated with improved duct connections in this preliminary analysis.

Improved Product Case Insulation

In the market and technology assessment, DOE identified insulation as a component to potentially improve portable AC performanc e. DOE found that the cases had little or no insulation, and based on the February 2015 Test Procedure NOPR, the case heat transfer is included in the overall cooling capacity. Therefore, DOE identified case insulation as a potential improvement to eff

iciency. However, DOE observed that the average case surface temperature for products in its test sample was 82 °F. DOE expects that adding insulation to the product case would result in little or no improvement compared to existing product cases. Addition ally, as noted above, there is little room in the case to add additional components. Adding insulation would likely increase the overall case dimensions.

Part

- Load Technology Improvements

In the market and technology assessment, DOE identified v ariable

- speed compressors and thermostatic or electronic expansion valves to potentially improve portable AC performance. However, DOE notes that these design options would typically improve portable AC performance under varying conditions. The technologie s would help to optimize the refrigeration system performance to the specific indoor and outdoor conditions. Because the test procedure proposed in the February 2015 Test Procedure NOPR would be conducted under constant ambient conditions, incorporatin g these design options would have no measurable impact on performance. Accordingly, DOE did not further consider these design options in this preliminary engineering analysis.

5.5.5 Combined Tested and Modeled Performance
Based on the design options considere d at each efficiency level, DOE estimated the performance of units beyond its test sample. The test sample units served as the starting points for the incremental improvements at each efficiency level, so DOE could estimate the potential performance improv ements for specific units. Figure 5.5.5

. 1 presents efficiency and cooling results for each unit in DOE’s test sample , with the appropriate design optio ns applied for each efficiency level . At higher efficiency levels, unit performance increased in both EER c m and cooling capacity.5-23

Figure 5.5.5

. 1 Modeled Cooling Efficiency versus Cooling Capacity at Each Efficiency Level by Unit

Because a unit’s cooling capacity factors into the calculation of EER c m , DOE also considered how a unit’s power consumption changed at each efficiency level. Figure 5.5.5

. 2 presents the calculated power consumption versus cooling capacity for each unit at each efficiency level.5-24

Figure 5.5.5

. 2 Modeled Power Consumption versus Cooling Capacity at Each Efficiency Level by Unit

Figure 5.5.5

. 2 shows that the air flow configurations associated with E fficiency L evels 1 th rough 3 increase cooling efficiency by increasing cooling capacity. Power consumption for these efficiency levels increase s compared to the baseline because of the increased compressor and blower motor power consumption , as discussed in section 5.5.4.1 . At E fficiency L evel 4, cooling capacity increases slightly with the larger heat exchangers

, and power consumption decreases with improvements to the compressor and blower motor efficiencies.

From this plot, DOE observed that a linear relationship provided the best

- fit trend to the data points corresponding to units within the same efficiency level . This established the relationship between power draw and cooling capacity. Figure 5.5.5

. 3 shows the individual data points broken down by efficiency level and includes the linear trend for each efficiency level.5-25

Figure 5.5.5

. 3 Linear Trends Between Power Consumption and Cooling Capacity by Efficiency Level

DOE used these linear equations to develop curves relating EER c m to cooling capacity. As discussed in section 5.3.2 , the resulting curves are based on the following equation with the coefficients provided in Table 5.5.5

. 1

.

EER c m = Cooling Capacity

Power = Cooling Capacity

( A × Cooling Capacity + B )

Table 5.5.5

. 1 Portable AC Efficiency Level Equation Coefficients

Effi ciency Level A Coefficient (Wh/Btu) B Coefficient (W) Baseline 0.113 855.5 EL1 0.1201 685.4 EL2 0.1222 566.3 EL3 0.1256 426.9 EL4 0.1205 355.15-26 Figure 5.5.5

. 4 Efficiency Level Curves by Cooling Capacity

5.5.6 Cost Estimates

As described in section 5.4.3 , DOE developed estimates of MPCs for each unit in the teardown sample. Th e incremental costs provided below in Table 5.5.6

. 1 represent the additional costs manufacturers would incur by producing models at each efficiency level compared to the baseline.

Table 5.5.6

. 1 Incremental Portable AC Manufacturer Production Costs
Efficiency Level Incremental MPC (2013$)
Baseline $

- EL1 $ 4.09

EL2 $ 4.67
EL3 $ 5.26

EL4 $ 47.76

As discussed in section 5.5.4

, E fficiency L evels 1 through 3 represent changes to the air flow configuration. The small incremental costs at these efficiency levels represent the cost for an additional duct and larger blower motor. At E fficiency L evel 4, the incremental MPC is significantly higher due to the high

- cost design options incorporated at this level, including larger heat exchangers (and the additional cost of a larger case and internal components) and more efficient compressors and blower motors.