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Federal Register / Vol. 86, No. 127 / Wednesday, July 7, 2021 / Proposed Rules furnace fan specifies the medium speed airflow-control setting for the heating function for certain installations, which is the highest airflow-control setting specified for the heating function. In this scenario, the DOE definition for Default airflow-control setting instructs to test the medium airflowcontrol setting for heating, rather than the as shipped setting i.e., the low setting, since there are multiple airflow-control settings for the heating function and the medium setting is the highest setting specified. See id.
The inquiries DOE has received from manufacturers also indicate that some manufacturers may be interpreting the test procedure to require testing according to installation instructions printed on the control board. DOE notes that the same control board can be used across multiple products to reduce manufacturing complexity and cost, so instructions provided on a control board may not be applicable to every unit in which a control board is used, which could lead to contradictory specifications regarding the installed use of consumer furnace fans. For this reason, DOE specifies in the definition of default airflow-control setting that the manufacturer specifications for installed-use are those specifications provided for typical consumer installations in the product literature shipped with the product in which the furnace fan is installed.
Issue 3: DOE requests comment on whether further instruction is needed for determining the appropriate airflow control settings for testing.
Issue 4: In the event of conflicting airflow-control setting information across multiple sources, DOE seeks comment on what the hierarchy should be for following manufacturers instructions.
In inquiries received after the January 2014 Final Rule, manufacturers have stated that requiring testing of the highest airflow-control setting for a given function when presented with multiple airflow-control setting options may result in a control configuration that is not representative of field installation.
Issue 5: DOE requests information about configuration of control settings for field installations of furnace fans.
Specifically, for instances in which a manufacturer specifies multiple airflowcontrol settings for a given function, DOE requests information and data that could help inform which airflow-control setting would be most representative of consumer use, such as data indicating the frequency with which a furnace fan is installed using each of the specified airflow-control settings.

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In addition to specifying the airflowcontrol settings for testing, the DOE test procedure also specifies operating conditions e.g., temperature rise ranges and ESP ranges. See section 8 of Appendix AA. In some instances, manufacturers specify that an airflowcontrol setting is to be used only under certain specified conditions, which are typically expressed as a maximum recommended ESP or temperature rise range associated with each airflowcontrol setting. In such instances, the manufacturer-specified operating conditions may not be consistent with the operating conditions required by the DOE test procedure. As a result, the furnace fan would be tested at conditions outside of those specified by the manufacturer for the applicable setting, if the airflow-control setting is one that is required to be tested. Section 8 of Appendix AA requires measurements of the heating setting operating within the ESP range and the temperature rise range defined by the test procedure, regardless of the range specified by the manufacturer. The operating conditions required by DOE
are intended to produce results that measure energy efficiency during a representative average use cycle for furnace fans. See 79 FR 500, 504 Jan.
3, 2014.
Moreover, testing outside the conditions specified by the manufacturer may not be possible.
Because furnaces are designed with safety controls that will automatically shut off the furnace when the outlet temperature reaches a certain temperature threshold, if the unit is operated at conditions other than those it is designed for, it may shut down before testing can be completed. For example, a thermal cutout switch might trip during testing causing the unit to shut down if the outlet temperature exceeds the temperature threshold of the safety control.
Issue 6: DOE requests data on the operating conditions typically encountered in the field for furnace fans across the various design options and input capacities currently available on the market.
Issue 7: DOE requests information on whether and to what extent safety shutdowns have occurred during testing.
In other cases, furnace fans have airflow-control settings that are designated by the manufacturer as being suitable for multiple functions i.e., heating, cooling, circulation; however, in the field each setting would be used only for a single function. The function that the setting would be used for when installed varies depending on installation needs e.g., assignment of a
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given airflow-control speed that can be used either for heating or cooling may be based on design considerations such as the size of the cooling coil paired with the furnace. In some field installations, the furnace fan must be physically reconfigured or re-wired to assign a particular function to the desired airflow-control setting. As discussed in section II.A, Appendix AA
defines airflow-control settings as being configured so that they perform a certain function without manual adjustment other than interaction with a user-operable control such as a thermostat that meets the manufacturer specifications for installed use.
However, in cases where multiple functions are assigned to the same airflow-control setting, the current test procedure could be understood to require that the unit be tested in multiple functions, meaning that the unit would need to be manually reconfigured or rewired during testing.
For example, for a single-stage furnace fan, if the same airflow-control setting was designated as both the highest default heat function and the highest default constant-circulation function, then laboratory personnel would be required to first wire the fan motor to conduct the heating test at that airflow control setting, and later rewire the fan motor to conduct the constant circulation test at the same airflow control setting. Similarly, rewiring could be required for multi-stage or modulating furnace fans for which the same airflow control setting was the highest airflow control setting for constant circulation function and the highest airflow control setting for reduced heat function, and the setting was not able to be configured for both functions without reconfiguring or rewiring the setting. DOE notes that there is no requirement to test at a specific manufacturer specified airflow-control setting for cooling function for the DOE
test. See sections 8.6.1.1, 8.6.1.2, and 8.6, Appendix AA. Re-configuring or rewiring an airflow-control setting in such a manner would not be representative of how that unit is installed and operated in the field and conflicts with the requirement that an airflow-control setting perform a certain function without manual adjustment.
Issue 8: DOE seeks comment on whether there are furnace fans on the market for which the combination of control settings required by the DOE test procedure would require reconfiguration or re-wiring of the unit during testing under the current DOE
test procedure. DOE also requests information on whether manufacturers have plans to introduce such furnace
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