4-i

CHAPTER 4. SCREENING ANALYSIS

TABLE OF CONTENTS

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

4.2 SCREENED-OUT TECHNOLOGIES................................................................ 4-2

4.2.1 Furnace Fan Energy Efficiency (FER) Standards.................................... 4-2

4.3 REMAINING TECHNOLOGIES ....................................................................... 4-4

4.3.1 Furnace Fan Energy Efficiency Standards............................................... 4-4

4.3.2 Standby Mode and Off Mode Power Consumption Standards................ 4-4

LIST OF TABLES

Table 4.3.1 Screened-In Standby Mode and Off Mode Design Options......................... 4-4
4-1

4.1 INTRODUCTION

This chapter details the screening analysis that the U.S. Department of Energy 

(DOE) conducted in support of the direct final rule for energy conservation standards for 

residential furnace fans.

In the market and technology assessment (MTA; chapter 3), DOE presents an 

initial list of technologies that manufacturers can use to improve the energy efficiency of 

residential furnace fans and standby and off mode electrical power consumption for 

hydronic air handlers. The purpose of the screening analysis is to evaluate the 

technologies that improve product energy efficiency or reduce standby and off mode 

energy consumption to determine which technologies DOE should consider further in the 

rulemaking analyses. DOE consulted a range of parties, including industry and technical 

experts and others, to develop a list of technologies for consideration in the market 

assessment (see chapter 3 of the TSD). Some of these technologies can reduce annual 

energy consumption of products in actual applications but may not improve the annual 

fan efficiency ratio (FER) or reduce standby and off mode electrical power consumption.

This rating metric is measured according to DOE regulations at XXX. DOE removed 

from consideration those technologies that do not improve FER or reduce standby and off 

mode electrical power consumption per the DOE test procedures. DOE evaluated the 

remaining technologies pursuant to the criteria in the Energy Policy and Conservation 

Act (EPCA), as amended. (42 U.S.C. 6311-6317)

Section 325(o) of EPCA establishes criteria for prescribing new or amended 

standards designed to achieve the maximum improvement in energy efficiency. 

Furthermore, EPCA directs the Secretary of Energy to determine whether a standard is 

technologically feasible and economically justified. (42 U.S.C. 6295(o)(2)(A)(B)) In 

view of this requirement, 10 CFR Part 430 Subpart C, Appendix A, Procedures, 

Interpretations and Policies for Consideration of New or Revised Energy Conservation

Standards for Consumer Products (the Process Rule), guides DOE in its consideration 

and promulgation of new or revised product efficiency standards. These procedures 

elaborate on the statutory criteria provided in 42 U.S.C. 6295(o) and, in part, eliminate

problematic technologies early in the process of prescribing or amending an energy 

efficiency standard. In particular, DOE determines whether to eliminate from 

consideration any technology that presents unacceptable problems with respect to the 

following criteria:

Technological feasibility. Technologies that are not incorporated in commercial 

products or in working prototypes will not be considered further.

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.
4-2

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, sizes, capacities, and volumes that are 

substantially the same as products generally available in the U.S. at the time, it will not 

be considered further.

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. In sum, if DOE

determines that a technology, or a combination of technologies, has unacceptable impacts 

on the policies stated in section 5(b) of the Process Rule, it will be eliminated from 

consideration. If a particular technology fails to meet one or more of the four criteria, it 

will be screened out from further consideration in the engineering analysis. 61 FR 36974-

36987; 10 CFR part 430, subpart C, appendix A, section (5)(b). The reasons for 

eliminating any technology are documented in section 4.2.

4.2 SCREENED-OUT TECHNOLOGIES

This section describes the technologies that DOE eliminated based on 

consideration of the following four factors: 1) technological feasibility; 2) practicability 

to manufacture, install, and service; 3) adverse impacts on product utility or product 

availability; and 4) adverse impacts on health or safety.

4.2.1 Furnace Fan Energy Efficiency (FER) Standards

DOE eliminated the following technology options for residential furnace fans

from further consideration: housing design modifications; and airflow path design.

4.2.1.1 Housing Design Modifications

DOE investigated housing design modifications during its teardown analysis. 

DOE found that housing designs did not vary dramatically between baseline and higherefficiency models or across manufacturers. In addition, DOE found no quantitative data 

correlating specific housing design modifications with efficiency improvements. 

Manufacturers also estimated that housing improvements would have very little effect on 

fan efficiency during manufacturer interviews. For these reasons, DOE is not including 

improved housing designs as a technology option.

4.2.1.2 Airflow Path Design

DOE recognizes that the airflow path design of the HVAC product in which the 

furnace fan is used impacts efficiency. DOE anticipates that modifying the size of the 

cabinet and the geometry of the heat exchanger(s) would be the primary considerations 

for improving airflow path design. Alterations to the design and configuration of internal 

components, such as the heat exchanger, could impact the thermal performance of the 

HVAC product. For the preliminary analysis, DOE was unable to confirm that heat 

exchanger modifications would not reduce thermal performance and result in reduced 
4-3

system efficiency. In addition, HVAC products that use furnace fans have space 

constraints. Any increase in overall size of the product could reduce utility to the 

consumer by potentially reducing or eliminating product availability for certain 

applications. While DOE did account for the impacts of airflow path design in the 

proposed test procedure and other aspects of the preliminary analyses (e.g., product class 

selection), DOE did not consider airflow path design as a technology option for these 

reasons. 

4.2.2 Standby Mode and Off Mode Power Consumption Standards

DOE eliminated the following standby mode and off mode technology options for 

residential furnace fans from further consideration: ECM control relay.

4.2.2.1 ECM Control Relay

While PSC blower motors do not draw any power when off, ECM blower motors

and their associated controls consume an average of 3 watts in order to provide power to

an integral control board for modulating the fan speed. To reduce standby power 

consumption of a furnace and off mode consumption of a central air conditioner or heat 

pump equipped with an ECM blower, DOE considered adding a relay to the circuit to 

disconnect the blower motor’s control circuit when not in use. A typical relay activates a 

switch when current runs through it, and a spring holds the switch open when there is no 

current flow. Manufacturer feedback provided during the interview process (see chapter 

12 of this TSD) indicated that ECMs are subject to an inrush of current upon startup. The 

power supply on the ECM’s control board, which is typically a switching mode power 

supply, cannot withstand the repeated surge of current that occurs at ECM startup and,

therefore, completely depowering and reactivating the motor by use of a control relay

would shorten the motor’s lifetime significantly. DOE considers a premature failure of 

the blower to be a reliability issue that has an adverse impact on product utility to the 

consumer. Therefore, DOE believes that disconnection of an ECM fan motor when the 

blower is not in use should not be considered in the engineering analysis. In addition,

DOE has not found any HVAC products that utilize a control relay or other mechanism to 

disconnect the ECM fan when the product in standby or off mode. Therefore, DOE did 

not consider this technology option for this rulemaking.
4-4

4.3 REMAINING TECHNOLOGIES

After eliminating those technologies that have no effect or do not increase energy 

efficiency and screening out those technologies that that do not meet the requirements of 

sections 4(a)(4) and 5(b) of the Process Rule, DOE considered the technologies in the 

following sections.

4.3.1 Furnace Fan Energy Efficiency Standards

For its FER standards rulemaking analysis, DOE considered the following 

technology options:

• Higher efficiency fan motors

• Higher efficiency fan blades (backward-curved impellers)

• Inverter technology

4.3.2 Standby Mode and Off Mode Power Consumption Standards

Because DOE is required by EPCA, as amended by EISA 2007, to include a 

descriptor for standby mode and off mode energy consumption for residential furnaces 

and a descriptor for off mode energy consumption for central air conditioners and heat 

pumps, a separate screening analysis was conducted for standby and off mode design 

options. (42 U.S.C. 6295(gg)(2)(A))

DOE identified the following design options that are capable of reducing the 

standby and off mode electrical power consumption of hydronic air handlers:

Table 4.3.1 Screened-In Standby Mode and Off Mode Design Options

Design Option Hydronic Air 

Handlers

Toroidal transformer X

Switching mode power supply X