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Federal Register / Vol. 86, No. 180 / Tuesday, September 21, 2021 / Proposed Rules
in the Federal Register on July 3, 2014.
79 FR 38130. Separately, DOE has established an energy conservation standard for furnaces governing the energy efficiency of active mode 10
CFR 430.32e1ii and also established standards for furnace standby mode and off mode electrical power consumption 10 CFR
430.32e1iii.
DOE first evaluated whether it would be possible to establish a standard in terms of AFUE2 without increasing the maximum allowable energy use or decreasing the minimum required efficiency of furnaces excluding during standby mode and off mode operation and/or furnace fans i.e., whether a standard could be prescribed in terms of AFUE2 without violating EPCAs antibacksliding provision.
A combined metric i.e., AFUE2 for furnaces and furnace fans would reflect the total energy consumption from both the furnace and furnace fan. In its petition, AHRI described the concept of the AFUE2 metric as follows: The AFUE2 metric accounts for furnace fuel, fan power, and stand-by and off-mode power consumption. The measured value represents the sum of usable heat and fan benefit, divided by the total fuel and electricity consumed. AHRI, No. 2
at p. 2 As a result of combining the various metrics into a single metric, manufacturers would be able to make tradeoffs between the efficiencies of the various covered products e.g., using a less-efficient fan while improving the efficiency of fuel consumption, which could lead to the efficiencies of either covered product i.e., either the furnace or furnace fan decreasing below the currently applicable energy conservation standard.
As an example, if a single energy conservation standard were established for furnaces and furnace fans using the AFUE2 metric that is of equivalent stringency to the current minimum AFUE and maximum standby mode and off mode power consumption levels required for furnaces, and the maximum FER levels allowed for furnace fans, then a furnace paired with a highly efficient furnace fan could potentially have a fuel consumption efficiency i.e., AFUE less than what is currently required under the AFUE standards e.g., less than 80 percent AFUE for nonweatherized gas furnaces, resulting in backsliding for the furnace efficiency as compared to the existing AFUE
standard. Similarly, an AFUE2 standard could be met by pairing a furnace with a high AFUE e.g., over 90 percent with an inefficient furnace fan that that would not separately meet the existing FER requirement. Furnaces with high
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AFUE ratings could also potentially meet AFUE2 standards despite having standby mode and/or off mode power consumption that are not compliant with current requirements.
The CA IOUs provided test data for two units tested to the AFUE, FER, and AFUE2 test procedures that illustrated the risk of backsliding. The two units tested were both non-weatherized gas furnaces, and both had 80-percent AFUE ratings, input capacities of 60,000
Btu/h, and maximum blower rated airflows of 1,200 CFM. One unit referred to as unit under test UUT
01 had a permanent split capacitor blower motor and an FER rating of 359
Watts per 1,000 cfm which is noncompliant with the existing standard for furnace fans at 10 CFR 430.32y. The other unit UUT02 had a blower with a multi-speed electrically commutated motor and an FER rating of 233 Watts per 1,000 cfm which is compliant with the existing standard for furnace fans at 10 CFR 430.32y. Despite the significant differences in fan motor efficiencies, the AFUE2 ratings were only 1.3 percent different.9 CA IOUs, No. 27 at pp. 13 These test results illustrate how efficiency improvements associated with a high-fuel-efficiency furnace could offset efficiency decreases from using a low-efficiency furnace fan at a given AFUE2 rating i.e., illustrating how under a unified metric, implementing a high-efficiency furnace technology could enable backsliding of furnace fan energy efficiency. Thus, if DOE were to adjust its existing furnaces energy conservation standards to now also capture fan energy use, it would only impact minimally compliant products and arguably grant an improper reprieve to products at the higher end of the efficiency marketplace. Additionally, as was also discussed by the CA IOUs, the data provided by AHRI in its AFUE2 Petition Exhibit 2 Example Calculations 10
suggests that units with a wide range of FER ratings including those that are compliant with the current FER
requirements and those that are not can have the same AFUE2 ratings. CA
IOUs, No. 27 at pp. 34 As a result of these findings, DOE has determined that adopting a single AFUE2 metric would violate EPCAs anti-backsliding 9 The CA IOUs did not measure jacket losses during testing and used the default value of 1
percent, as is allowed by the furnace test procedure at Appendix N if a jacket lost test is not conducted.
The CA IOUs also estimated the AFUE2 results with a jacket loss factor of 0.3 percent, and the difference in ratings between UUT01 and UUT02 in that case was 1.2 percent.
10 The original data provided by AHRI can be found at www.regulations.gov/document/EERE2018-BT-PET-0017-0002 as Exhibit 2.

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provisions because it would allow decreases in the energy efficiency of individual covered products.
In evaluating the AHRI petition, DOE
also separately sought to determine whether it would be feasible to integrate the active mode energy use and standby mode and off mode power consumption into an integrated metric. DOE has previously determined in a final rule published in the Federal Register that it is not feasible to establish an energy conservation standard for furnaces that integrates electrical standby mode and off mode energy use. 75 FR 64621, 64623 Oct. 20, 2010; October 2010
final rule. In the October 2010 final rule, DOE concluded that it would not be technically feasible to develop an integrated metric combining electrical standby mode and off mode energy consumption into the calculation of overall annual energy consumption of those products because the standby mode and off mode energy usage, when measured, is essentially lost in practical terms due to the fact that manufacturers ratings of AFUE are presented to the nearest whole number. Id. Although furnace ratings are now reported to the tenth place for compliance certification purposes see 10 CFR 429.18a2vii, standby mode and off mode power consumption is substantially less than active mode power consumption and may not be apparent in the measured energy use of a furnace, and it does not change the fact that DOEs furnace energy conservation standards using the AFUE metric continue to be set at the nearest whole number. As such, a combined metric would likely not provide consumers any meaningful information as to the standby mode and off mode energy use of a furnace and may disincentivize manufacturers from making improvements to standby mode and off mode furnace efficiency.
DOE estimates that the electrical standby mode and off mode power consumption typically make up less than one percent of the combined furnace and furnace fan energy consumption, meaning that small increases in standby mode and off mode consumption would have little bearing on the AFUE2 rating. In its review of data provided by AHRI as part of its petition, DOE noted that a hypothetical doubling of the standby mode power consumption would result in a change of the AFUE2 result of less than half of one percent for each unit in the dataset.
The AHRI petition and accompanying data do not support DOE changing its prior determination that it is not be technically feasible to combine standby and off mode power consumption into a combined metric, and therefore, the
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