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CHAPTER 4. SCREENING ANALYSIS

TABLE OF CONTENTS

4.1 INTRODUCTION ........................................................................................................... 4-1

4.2 DISCUSSION OF TECHNOLOGY SCREENING........................................................ 4-2

4.2.1 Linear Compressors......................................................................................................... 4-3

4.2.2 Increased Evaporator Surface Area ................................................................................. 4-3

4.2.3 Improved Evaporator Heat Exchange.............................................................................. 4-3

4.2.4 Increased Condenser Surface Area .................................................................................. 4-4

4.2.5 Improved Condenser Heat Exchange............................................................................... 4-4

4.2.6 Forced-Convection Condensers....................................................................................... 4-4

4.2.7 Higher-Efficiency Fan Motors (for Non-Compressor Refrigerators).............................. 4-4

4.2.8 Higher-Efficiency Fan Blades.......................................................................................... 4-5

4.2.9 Improved Resistivity of Insulation................................................................................... 4-5

4.2.10 Gas-Filled Panels............................................................................................................. 4-5

4.2.11 Improved Gaskets, Double Gaskets, and Improved Door Face Frame............................ 4-5

4.2.12 Solid Door (for Cooled Cabinets).................................................................................... 4-6

4.2.13 Improved Expansion Valve.............................................................................................. 4-6

4.2.14 Fluid Control or Solenoid Valve...................................................................................... 4-7

4.2.15 Off-Cycle Defrost, Reduced Energy for Automatic Defrost, Adaptive Defrost, and 

Hot-Gas Bypass Defrost .................................................................................................. 4-7

4.2.16 Electronic Temperature Control ...................................................................................... 4-7

4.2.17 Conversion to Alternative Refrigeration System............................................................. 4-8

4.2.18 Component Location........................................................................................................ 4-9

4.3 REMAINING DESIGN OPTIONS ................................................................................. 4-9

LIST OF TABLES

Table 4.2.1 Thermoelectric COP Data......................................................................................... 4-8

Table 4.3.1 Retained Design Options........................................................................................ 4-10
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CHAPTER 4. SCREENING ANALYSIS

4.1 INTRODUCTION

This chapter discusses the screening analysis conducted by the U.S. Department of 

Energy (DOE) of the technology options identified in the market and technology assessment for 

miscellaneous refrigeration products (Chapter 3 of the preliminary technical support document 

(preliminary TSD)). In the market and technology assessment, DOE presented an initial list of 

technology options that can be used to reduce energy consumption of each of the products 

covered in this rulemaking. The goal of the screening analysis is to identify any technology

options that will be eliminated from further consideration in the rulemaking analyses.

For each product, the corresponding candidate technology options are assessed based on 

DOE analysis as well as inputs from stakeholders including manufacturers, trade organizations, 

and energy efficiency advocates. Technology options which are judged to be viable approaches 

for improving energy efficiency are retained as inputs to the subsequent engineering analysis. 

Technologies that pass through the screening analysis are referred to as “design options” in the 

engineering analysis. Technology options which are not incorporated in commercial products or 

in working prototypes, or that fail to meet certain criteria as to practicability to manufacture, 

install and service, as to impacts on product utility or availability, or as to health or safety will be 

eliminated from consideration in accordance with Energy Conservation Program for Consumer 

Products: Procedures for Consideration of New or Revised Energy Conservation Standards for 

Consumer Products. 61 FR 36974, sections 4(a)(4) and 5(b).

The technologies identified in the market and technology assessment were evaluated 

pursuant to the criteria set out in The Energy Policy and Conservation Act, as amended (EPCA 

or the Act). (42 U.S.C. 6291-6317) EPCA provides criteria for prescribing new or amended 

standards, which will achieve the maximum improvement in energy efficiency the Secretary of 

Energy determines to be technologically feasible. (42 U.S.C. 6295(o)(2)(A)) It also establishes 

guidelines for determining whether a standard is economically justified. (42 U.S.C. 

6295(o)(2)(B)) In view of the EPCA requirements for determining whether a standard is 

technologically feasible and economically justified, Appendix A to subpart C of Title 10 Code of 

Federal Regulations Part 430 (10 CFR Part 430), Procedures, Interpretations and Policies for 

Consideration of New or Revised Energy Conservation Standards for Consumer Products (the 

Process Rule), sets forth procedures to guide DOE in the consideration and promulgation of new 

or revised product efficiency standards under EPCA. These procedures elaborate on the statutory 

criteria provided in 42 U.S.C. 6295 and in part eliminate problematic technologies early in the 

process of revising an energy efficiency standard. Under the guidelines, DOE eliminates from 

consideration technologies that present unacceptable problems with respect to the following four 

factors: 
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(1) Technological feasibility. If it is determined that a technology has not been 

incorporated in commercial products or in working prototypes, then that technology will not be 

considered further.

(2) Practicability to manufacture, install, and service. If it is determined that mass 

production of a technology in commercial products and reliable installation and servicing of the 

technology could not be achieved on the scale necessary to serve the relevant market at the time 

of the effective date of the standard, then that technology will not be considered further.

(3) Impacts on product utility to consumers. If a technology is determined to have 

significant adverse impact on the utility of the product to significant subgroups of consumers, or 

results in the unavailability of any covered product type with performance characteristics 

(including reliability), features, size, capacities, and volumes that are substantially the same as 

products generally available in the United States at the time, it will not be considered further. 

(4) Safety of technologies. If it is determined that a technology will have significant 

adverse impacts on health or safety, it will not be considered further.

The following section details the technology options that were screened out for each 

product covered by this rulemaking and the reasons why each were eliminated.

4.2 DISCUSSION OF TECHNOLOGY SCREENING

For the products in this rulemaking, the screening criteria specified in section 4.1 were 

applied to the technology options to either retain or eliminate each technology from the 

engineering analysis. DOE also eliminated some technologies that were determined to provide 

little or no potential for energy use reduction for one of the following additional reasons: (a) the 

technology is already used in baseline products and is incapable of generating additional energy 

efficiency or reducing energy consumption, (b) the technology does not reduce energy use, and 

(c) there is insufficient data demonstrating benefit of the technology.

For all products, DOE screened out linear compressors, increased evaporator surface 

area, improved evaporator heat exchange, increased condenser surface area, improved condenser 

heat exchange, forced-convection condensers, higher-efficiency fan blades, improved resistivity 

of insulation, gas-filled panels, improved gaskets, double gaskets, improved door face frames, 

solid doors, improved expansion valves, fluid control or solenoid valves, off-cycle defrost, 

reduced energy for automatic defrost, adaptive defrost, hot-gas bypass defrost, electronic 

temperature control, conversion to thermoelectric or absorption refrigeration systems, and 

component location for the reasons that follow. DOE also screened out conversion to vapor 

compression and higher-efficiency fan motors for non-compressor refrigerators.
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4.2.1 Linear Compressors

While promising potential has been reported for linear compressors, DOE does not have 

sufficient information about commercially available linear compressors to allow accurate

prediction of the performance and cost impacts of this technology. 

Moreover, the LG design is proprietary, as discussed in section 3.3.3.1. Embraco is 

inviting co-development partnerships for their Wisemotion linear technology,1 but DOE does not 

have information about restrictions and limitations that may be associated with such 

partnerships. Other compressor manufacturers who have indicated that they have investigated 

linear technology have stated that linear compressor technology does not provide a clear path to 

improved efficiency, and some have indicated that they are no longer actively pursuing this 

technology. Consequently, DOE concludes that the potential for widespread use of linear 

compressors is not certain. For these reasons, DOE has eliminated linear compressors from 

further consideration in the analyses.

4.2.2 Increased Evaporator Surface Area

Increasing the heat exchanger surface area can be achieved by increasing the face area of 

the evaporator or adding more tube rows. These measures are limited by the geometry of the 

cooled cabinet. Most compact cooled cabinets use roll-bond or coldwall evaporators that are 

located along the back (for roll-bond designs) or side (for coldwall designs) walls of the cabinet. 

Such designs typically take advantage of all available wall space; therefore, there is little to no 

room for growth in these products. For these reasons, DOE has eliminated this design option 

from further consideration for cooled cabinets.

4.2.3 Improved Evaporator Heat Exchange

Improving heat exchanger performance can be achieved through the use of enhanced fins 

and/or tubes. These types of fin and tube enhancements are common in air-conditioning 

applications where slit and louvered designs are used to enhance the fin surface and different 

types of internally-grooved surfaces are used to enhance the tubing. Application of similar 

enhancements in cooled cabinet evaporators is complicated by the potential for frost 

accumulation on the evaporators when the operating at the lower end of their compartment 

temperature range. In order to avoid the energy use associated with frequent defrost, fin spacing 

in the evaporators of refrigeration products is comparatively sparse. During defrost, the typical 

flat fin design of these evaporators assures that the frost slides rapidly off the fins and doesn’t get 

stuck on fin enhancement features. The low fin density allows the evaporator to work effectively 

without blocking airflow with a considerable accumulation of frost. Although little or no frost 

accumulation may occur in energy testing conducted using a 55  ̊F standardized compartment 

temperature for cooled cabinets, these products generally also are designed to operate with 

compartment temperatures down to 40  ̊F or lower, for which evaporator temperature generally 
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would be below freezing. DOE has eliminated this option from consideration in the subsequent 

analysis for cooled cabinets.

4.2.4 Increased Condenser Surface Area

Increasing the heat transfer surface area of condensers can be achieved by (a) increasing 

the width of the rows of tubes, (b) adding more tube rows along the direction of air flow, or (c) 

adding more tube rows across the direction of air flow. However, such measures are constrained

by the geometry of the cooled cabinet. Most cooled cabinets have their condensers located

underneath the cabinet in a small compressor compartment; however, DOE observed that space 

for condenser growth was very limited in the units that it examined during its reverseengineering analysis. Therefore, DOE has eliminated this option from consideration in the 

subsequent analysis for cooled cabinets.

4.2.5 Improved Condenser Heat Exchange

Use of heat exchanger enhancements for the condenser is complicated by the need for 

adequate performance when the heat exchanger has not been cleaned. Most cooled cabinets’

condensers (other than hot wall condensers integrated into the outer shells of the products) are 

made of either steel tubes with steel wire fins or copper tubes with widely-spaced aluminum fins. 

These condensers have a very open construction which reduces the impact on performance of 

dust collecting on the condenser surfaces. High-density flat fin condensers are known to require 

more careful attention to cleaning, which occurs infrequently or never in consumer refrigeration 

products.

4.2.6 Forced-Convection Condensers

Some smaller, “countertop” cooled cabinets use hotwall condensers. However, most 

undercounter and standard-size cooled cabinets already use forced-convection condensers. 

Therefore, DOE has eliminated this option from consideration in subsequent analyses.

4.2.7 Higher-Efficiency Fan Motors (for Non-Compressor Refrigerators)

In its reverse-engineering analysis, DOE found that non-compressor refrigerators 

typically utilize brushless DC fan motors. Therefore, because this technology is already widely 

implemented in baseline units, DOE elected not to consider it as a design option for noncompressor refrigerators. However, DOE retained this design option for cooled cabinets, which 

typically do not utilize brushless DC fan motors.
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4.2.8 Higher-Efficiency Fan Blades

Cooled cabinet fan blades use an axial design. They are typically injection molded plastic 

with a three-dimensional shape for improved performance as compared with older stamped sheet 

metal designs. There is in general little data available to quantify the energy benefit possible with

further improvement in fan blade design in today’s refrigeration products. Fan performance is 

highly dependent on details of integration with the system: orifice geometry, tolerance of 

blade/orifice gap, match of system flow impedance to fan performance, etc. Hence, making 

credible estimates of energy savings potential through fan blade replacement requires testing fan 

blade swaps in baseline products. The cost of fabrication of improved fan blade geometries 

would be not be significantly higher than that of current designs, so most of the cost increase 

associated with this technology option would be associated with paying for the blade 

development, tooling, and/or licensing fees. During discussions with manufacturers, no 

information was provided which would allow credible calculation of savings and costs associated 

with improved fan blades. Hence, DOE has eliminated this option from further consideration.

4.2.9 Improved Resistivity of Insulation

Past research has demonstrated that the resistivity of polyurethane (PU) foam insulation 

can be improved through the use of additives that reduce the thermal conductivity of the foam.

Discussion with manufacturers has confirmed that there are no available options for 

improvement in PU foam insulation performance (other than reverting to use of banned blowing 

agents). Due to the lack of available information and the predictions that there is no significant 

benefit to be expected from PU foam improvements, DOE has eliminated this option from 

consideration in the engineering analysis.

4.2.10 Gas-Filled Panels

Investigation of the status of gas-filled panels suggests that there has been some 

evaluation of this technology by manufacturers of consumer refrigeration equipment, but that no 

manufacturers are using it in their products. The costs are reported to be as high as for vacuum 

insulation panels (VIPs), with less reduction in thermal load. DOE has not been able to identify a 

credible supplier that would provide gas filled panel products to the refrigeration industry. 

Consequently, DOE has eliminated this technology from further consideration.

4.2.11 Improved Gaskets, Double Gaskets, and Improved Door Face Frame

Past investigation on reduction of heat load in the gasket and door face frame area has 

focused on (1) limiting the conduction of heat through metal casing material passing underneath 

the gasket magnet on the cabinet side or in the region of the gasket clip on the door side into the 

cabinet interior, (2) using a gasket which provides additional cover of frame surfaces towards the 

interior of the magnet to prevent cold air from reaching the high-conductivity metal casing near 

the gasket magnet, and (3) providing a long thin “throat” area between the gasket and the interior 
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to limit convection heat transfer, although this is not generally done with glass doors. Most 

current designs are effective in addressing these issues. 

Limited information is publicly available which would allow quantification of additional 

improvement potential for the door frame/gasket area of cooled cabinets, hybrid refrigeration 

products, and ice makers. Some manufacturers use extra-strong gasket magnets to limit 

infiltration and thermal loss, but it is unclear whether significant thermal improvement is 

possible with such systems. Manufacturers during the 2011 Residential Refrigeration Products 

Rulemaking indicated during technical discussions that properly designed and installed gasket 

systems provide a tight seal and that there isn’t any further reduction in air leakage that could be 

achieved with improvements in the gasket system such as increasing the magnetic force.2 In

addition, consumer safety laws preclude use of excessive door sealing force. 

It is expected that incremental improvement may be possible for some products; 

however, the lack of good quantified information on general improvement potential in this area 

makes these technology options unsuitable for consideration as design options.

4.2.12 Solid Door (for Cooled Cabinets)

Replacing the glass door with a solid door, although it would notably improve energy 

efficiency, would negatively impact cooled cabinets’ consumer utility by eliminating one of its 

dual functions, the display of the products stored within. Discussions with manufacturers have 

indicated that cooled cabinets with solid doors would be much less desirable to consumers. 

Hence, DOE has eliminated this option from further consideration.

4.2.13 Improved Expansion Valve

Miscellaneous refrigeration products exclusively use capillary tubes for refrigerant flow 

metering. These tubes are inexpensive and they lend themselves easily to low-cost fabrication of 

suction line heat exchangers by brazing the capillary to the suction line. Automatic, adjustable 

thermostatic or electronic expansion valves are available, but they generally are oversized for 

consumer products such as cooled cabinets and refrigerators. Furthermore, it is unclear whether 

there is any potential for energy savings using alternative expansion devices. DOE has proposed

energy tests for miscellaneous refrigeration products using a single fixed ambient air temperature 

(90 °F for vapor-compression cooled cabinets, non-compressor refrigerators, and hybrid 

refrigeration products; 72 °F for ice makers and non-compressor cooled cabinets). A capillary 

tube can be designed to provide optimized performance for the single test condition. Systems are 

generally designed to operate with evaporator exit conditions having little or no superheat during 

energy testing, thus maximizing use of the evaporator. In the lower ambient temperature typical 

in homes, the pressure available to move refrigerant through the capillary tube is lower, thus 

possibly leading to increased superheat and less than optimum performance. An automatic valve 

could provide optimum performance for a wider range of operating conditions, but such 
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improvement would not be reflected in energy testing. DOE has eliminated this option from 

further consideration.

4.2.14 Fluid Control or Solenoid Valve

Off-cycle refrigerant migration reduces a refrigeration product’s efficiency by allowing 

warm and/or vapor-phase refrigerant to pass into the portion of the refrigeration system inside 

the cabinet. A fluid control or solenoid valve installed downstream of the condenser can be used 

to prevent such refrigerant migration. Research has demonstrated that solenoid valves can yield 

substantial energy savings.3 Although many dual-zone cooled cabinets use similar solenoid 

valves to allow control of multiple compartments with a single compressor, use of these valves 

may present a possible reliability issue. Also, operation with an off-cycle valve requires that the 

compressor motor be capable of starting up against a substantial pressure difference. The starting 

windings of compressors that can do this reliably over the life of a refrigerator draw more power 

and hence reduce the compressor’s steady-state efficiency. The different efficiency levels of 

commercial refrigeration compressors designed for instant restart versus restart after pressure 

equalization have energy efficiency ratio (EER) ratings which differ by 10 percent or more. Such 

a difference would be expected for residential compressors operating with an off-cycle valve, 

and this difference would more than neutralize any benefit accrued from using the off-cycle 

valve. Hence, DOE has eliminated this option from further consideration.

4.2.15 Off-Cycle Defrost, Reduced Energy for Automatic Defrost, Adaptive Defrost, and 

Hot-Gas Bypass Defrost

DOE has identified a few cooled cabinets that use active heater defrost; however, the vast 

majority of miscellaneous refrigeration products use passive (off-cycle) or manual defrost. 

Because these four design options are only relevant to products that use active heater defrost, 

they will not be applicable to most products. Hence, DOE has eliminated these options from 

further consideration.

4.2.16 Electronic Temperature Control

DOE has not identified any relevant information showing the energy benefit of electronic 

temperature control. Potential benefits of electronic control when operating with single-speed 

compressors are fine-tuning of the run times and fine-tuning of the cut-in and cut-out 

temperatures. While there may be potential for incremental improvement associated with such 

fine-tuning, the lack of data supporting claims for energy savings make it difficult to properly 

analyze this option.
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4.2.17 Conversion to Alternative Refrigeration System

Thermoelectric cooling technology currently does not achieve efficiency levels which 

make it attractive as a design option alternative to vapor compression technology for improving 

cooled cabinet energy efficiency. Because data on the efficiency of thermoelectric modules is 

limited, DOE conducted energy consumption and reverse-heat-leak testing to calculate the 

coefficient of performance (COP) of five thermoelectric refrigerators. During the reverse-heatleak test, DOE placed electrical heaters inside the refrigerators and determined the heater wattage 

necessary to maintain a refrigerator cabinet temperature of 90 °F in an ambient temperature of 

approximately 39 °F, corresponding to the reverse of the conditions required for the energy test. 

DOE calculated COP for thermoelectric modules using Equation 1:

Equation 1

CCC = Qheeeee

( r − ∑ f)

Where:

QH is the average power of the heater during the reverse-heat-leak test, in Watts;

Pref is the average power of the refrigerator at a compartment temperature of 39 °F, 

determined during the energy test, in Watts; and

Pfan is the sum of the average power of all fans in the refrigerator, in Watts.

These test results, which account solely for the efficiency of the refrigeration system in 

that they do not include parasitic fan power, are presented in Table 4.2.1.

Table 4.2.1 Thermoelectric COP Data

Storage Volume (ft3) COP

0.25 0.093

0.87 0.16

1.6 0.14

1.7 0.18

1.7 0.14

In comparison, the lowest compressor COP in the capacity range most utilized by 

miscellaneous refrigeration products (300-400 Btu/hour) is 0.9 (equivalent to an EER of 3.0), 

which is five to ten times the COP measured for the thermoelectric modules as listed above. 

Hence, DOE has not considered conversion to thermoelectric technology as a design option for 

vapor-compression products in the engineering analysis. DOE has also screened out heat pipes, 

which are only implemented as part of thermoelectric refrigeration systems, from its cooled 

cabinet analysis.

Because vapor-compression technology is more efficient than thermoelectric technology, 

DOE has considered conversion to vapor compression as a design option for non-compressor 
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cooled cabinets. However, DOE has not considered this design option for non-compressor 

refrigerators because vapor-compression refrigerators are part of DOE’s existing authority for 

coverage; they are part of a different set of products that have their own different standard levels.

4.2.18 Component Location

Locating the compressor at the top of the cooled cabinet was noted as a potential 

technology option. However, this change would increase structural requirements for the cabinet, 

increase risk of product tip-over, and provide much less practical use of space from the consumer 

perspective. It also makes design for re-evaporation of defrost water more challenging. It is 

unlikely that the savings would justify all of these drawbacks.

Another option is to locate the evaporator fan motor outside the cabinet to reduce 

internal loads from the heat loss of the motor. Evaporator fan motor input wattages are now in 

the range of 3 W to 7 W, with fan blade efficiency in the range of 20 percent to 30 percent and 

motor efficiency in the range of 20 percent to 50 percent. Hence, load reduction associated with 

moving the motor loss outside the cabinet is only in the range of 1 W to 5 W for the portion of 

time during which the evaporator fan is in operation, which is typically less than 50 percent of 

total operating time. The loss associated with the added infiltration and conduction is likely to be 

comparable to the savings from the fan relocation. Additional issues with this approach include 

reliability, reduced design flexibility, and the fact that reduction of motor losses (by using more 

efficient fan motors) may be a more effective approach to reducing the impact of the fan motor 

power input. 

No options for relocation of components have been identified which merit further 

consideration in the engineering analysis.

4.3 REMAINING DESIGN OPTIONS

Table 4.3.1 lists the design options that were retained by DOE for cooled cabinets and

non-compressor refrigerators, the two product categories for which DOE performed design 

option analysis. Each of these technologies were considered in the engineering analysis.
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Table 4.3.1 Retained Design Options

Design Option Cooled Cabinets Non-Compressor 

Refrigerators

Improved compressor efficiency 

Variable-speed compressors 

Forced-convection evaporator 

Higher-efficiency fan motors 

Increased insulation thickness  

Vacuum-insulated panels  

Improved resistivity of glass door 

Conversion to vapor compression 

Heat pipe 
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REFERENCES

 

1 < http://www.embraco.com/wisemotion/Default.aspx>(Accessed September 19, 2014)

2 U.S. Department of Energy-Office of Codes and Standards. Technical Support Document: Energy Efficiency 

Standards for Consumer Products: Refrigerators, Refrigerator-Freezers, and Freezers, September, 2011. 

Washington, DC. EERE-2008-BT-STD-0012.

3 Coulter, W.H. and Bullard, C.W. “ An Experimental Analysis of Cycling Losses in Domestic RefrigeratorFreezers,” ASHRAE Transactions, 1997. Vol. 103, Pt. 1.