CHAPTER 4. SCREENING ANALYSIS

TABLE OF CONTENTS

4.1 INTRODUCTION ........................................................................................................... 4-1 4.2 SCREENED

- OUT TECHNOLOGY OPTIONS ............................................................. 4-1 4.2.1 Electro

- hydrodynamic enhanced heat transfer ..................................................... 4-2 4.2.2 Alternative refrigerants ........................................................................................ 4-2 4.2.3 Sub- coolers .......................................................................................................... 4-3 4.3 REMAINING DESIGN OPT IONS ................................................................................. 4-3

LIST OF TABLES

Table 4.3.1 Retained Design Options for Small, Large, and Very Large Air-Cooled CUAC and CUHP .......................................................................................... 4-3

4-iCHAPTE R 4. SCREENING ANALYSIS

4.1 INTRODUCTION
This chapter details the screening analysis conducted by the U.S. Department of Energy (DOE) of the technology options identified in the market and technology assessment (chapter 3 of this technical support document (TSD)) for small, large, and very large
, air

- cooled commercial package air con ditioning and heating equipment (also referred to in this notice as small, large, and very large air -cooled commercial unitary air conditioners, CUAC, and small, large, and very large air

- cooled commercial unitary heat pumps, CUHP). In the market and technology assessment, DOE presented an initial list of technologies that can be used to increase the efficiency of the considered equipment. The goal of the screening analysis is to identify any technology options that will be eliminated from further consideration in the rulemaking analyses.

T he candidate technology options are assessed based on DOE ’s analysis as well as inputs from interested parties including manufacturers, trade organizations, and energy efficiency advocates. Technology options that are judged to be viable approaches for improving efficiency are retained as inputs to the subsequent e ngineering a nalysis , and are designated as design options. Technology options that are not incorporated in commercial equipment or in working prototypes, or that fail to meet certain criteria
, as to practica bility to manufacture, install and service, as to impacts on product utility or availability, or as to health or safety will be eliminated from consideration. The rationale for either screening out or retaining each technology option is detailed in the following sections.

4.2 SCREENED

- OUT TECHNOLOGY OPTIONS
The following section details the specific technology options that were screened out prior to the engineeri ng analysis, along with the rationale for elimination.

The technologies identified in the market and technology assessment were evaluated pursuant to the criteria set out in the Energy Policy and Conservation Act ( EPCA ). (42 United States Code ( U.S.C.) 6291-6317) DOE consulted with industry, technical experts, and other interested parties in developing a list of design options. DOE then applied the following set of screening criteria to determine which design options are unsuitable for further consideration in the rulemaking:

(1) Technological feasibility

. If it is determined that a technology has not been incorporated in commercial equipment 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 equipment and reliable installation and servicing of the technology could not be achieved on the scale necessary to serve the releva nt market at the time of the effective date of the standard, then that technology will not be considered further.

4-1(3) Impacts on product utility to consumers

. If a technology is determined to have significant adverse impact on the utility of the equipment to significant subgroups of consumers, or result s in the unavailability of any covered equipment type with performance characteristics (including reliability), features, size, capacities, and volumes that are substantially the same as equipment 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.

After reviewing the technology options to increase the efficiency of the covered equipment against the screening criteria
, DOE eliminate d the following technology options from consideration in its rulemaking analysis.

4.2.1 Electro

- hydrodynamic enhanced heat tra nsfer

Electro

- hydrodynamic enhance ment of heat transfer, which increases the net heat transfer coefficient by applying a high

- voltage electrostatic potential field across a heat transfer fluid to destabilize the thermal boundary layer and incite fluid mixing, is still in the research stage. Although the technique has been shown to improve heat transfer in laboratory testing, DOE is not aware of any commercially available equipment or working prototypes that use electro

hydrodynamic heat transfer. As a resu lt, DOE does not believe at this time that this option meets the screening criterion of technological feasibility. In addition, DOE notes that this technology has not been adequately demonstrated for commercial deployment and, as a result, does not meet th e criterion of practicability to install and service on a scale necessary to serve the relevant market at the time of the compliance date of a new standard. For these reasons, DOE did not consider electro

- hydrodynamic heat transfer further analys i s.

4.2.2 Alter native refrigerants DOE considered ammonia, carbon dioxide, and various hydrocarbons (such as propane and isobuta ne) as alternative refrigerants to those that are currently in use, such as R-410A. DOE notes that safety concerns need to be taken into consi deration when using ammonia and hydrocarbons in air- conditioning systems. The Environmental Protection Agency ( EPA ) created the Significant New Alternatives Policy (SNAP) Program to evaluate alternatives to ozone

depleting substances. Substitutes are reviewed on the basis of ozone depletion potential, global warming potential, toxicity, flammability, and exposure potential. DOE notes that ammonia (in vapor compression cycles), carbon dioxide, and hydrocarbons have been approved or are being considered under SNAP for certain uses, but these or other low GWP alternatives are not yet listed as acceptable substitutes for this equipment. a DOE is also not aware of any other more efficient refrigerant options that are SNAP -approved. Because these alternative refrigerants have not yet been approved for this equipment, DOE screened out ammonia, carbon dioxide, and

a On July 9, 2014, EPA proposed to list certain hydrocarbons and R

- 32 for residential self

- contained A/C appliances as acceptable subject to use conditions to address safety concerns (See 79 FR 38811). EPA is also evaluating new refrigerants for other A/C ap plications, including commercial A/C. Additional information regarding EPA’s SNAP Program is available online at: http://www.epa.gov/ozone/snap/

.

4-2hydrocarbons as alternative refrigerants for improving the energy efficiency of small, large, and very large air -cooled CUAC and CUHP.

4.2.3 Sub

- coolers

A sub- cooler is a device located between the condenser coil outlet and the expansion device inlet used to further cool the refrigerant exiting the condenser in order to achieve a higher cooling/heating capacity for a unit. DOE notes that air -cooled CUAC and CUHP typically sub

cool the refrigerant in the condensing coil ( i.e. , providing additional decrease in the temperature of the refrigerant ). DOE also notes that additional mechanical sub- cooling from smaller, secondary vapor-compression circuits has not been incorporated in commercial equipment or in working prototypes. As a result, DOE does not believe sub- cooling meets the criterion of technological feasibility and did not consider it for further analysis.

4.3 REMAINING DESIGN OPTIONS

Table 4.3.1 list s the technology options that were retained by DOE and subsequently designated as design options. Each of these technologies will be evaluated (consistent with equipment available on the market) further in the subsequent engineering analysis.

Table 4.3.1 Retained Design Options for Small, Large, and Very Large Air-Cooled CUAC and CUHP Condenser and evaporator fan and fan moto r improvements:

• Larger fan diameters

• More efficient fan blades (e.g., air foil centrifugal evaporator fans, backward

- cured centrifugal evaporator fans, high efficiency propeller condenser fans)

• High efficiency motors (e.g., copper rotor motor , high efficiency induction, permanent magnet, electronically commutated)

• Variable speed fans/motors Larger heat exchangers Microchannel heat exchangers Compressor Improvements

• High efficiency compressors

• Multiple compressor staging

• Multiple

- or variable

- capac ity compressors Thermostatic expansion valves Electronic expansion valves
Reduced indoor fan belt loss

• Synchronous (toothed) belts

• Direct

- drive fans

4-3