Appendix B - Appendix B to Subpart D of Part 431-Uniform Test Method for Measurement of the Energy Efficiency of Commercial Warm Air Furnaces (Thermal Efficiency Two)
Manufacturers must use the results of testing under this appendix B to determine compliance with any standards for commercial warm air furnaces that use the thermal efficiency 2 (TE2) metric. In addition, manufacturers may optionally make representations of energy use or efficiency of this equipment using TE2 as determined using this appendix starting on July 3, 2023.
0. Incorporation by Reference.
In § 431.75, DOE incorporates by reference the entire standard ANSI Z21.47-2021. However, only section 5.40 and Appendix J of ANSI Z21.47-2021 apply, as specified in sections 1.2 and 1.6 of this appendix.
1. Testing
1.1 Set up and test the unit according to sections 0 through 4 of appendix A to this subpart, while operating the unit at the maximum nameplate input rate (i.e., full load). Calculate thermal efficiency (TE) using the procedure specified in sections 3 and 4 of appendix A to this subpart.
1.2 For commercial warm air furnaces that are designed for outdoor installation (including but not limited to CWAFs that are weatherized, or approved for resistance to wind, rain, or snow), or indoor installation within an unheated space (i.e., isolated combustion systems), determine the jacket loss using Section 5.40 and Annex J of ANSI Z21.47-2021 while the unit is operating at the maximum nameplate input. The jacket shall consist of the surfaces surrounding the heating section of the furnace. The jacket includes all surfaces separating the heating section from the supply air, outside air, or condenser section, including the bottom surface separating the heating section from the basepan.
1.3 For commercial warm air furnaces that are designed only for indoor installation within a heated space, jacket loss shall be zero. For commercial warm air furnaces that are designed for indoor installation within a heated or unheated space, multiply the jacket loss determined in section 1.2 of this appendix by 1.7. For all other commercial warm air furnaces, including commercial warm air furnaces that are designed for outdoor installation (including but not limited to CWAFs that are weatherized, or approved for resistance to wind, rain, or snow), multiply the jacket loss determined in section 1.2 of this appendix by 3.3.
1.4 Subtract the jacket loss determined in section 1.3 of this appendix from the TE determined in section 1.1 of this appendix to determine the full-load efficiency.
1.5 Set up and test the unit according to sections 0 through 4 of appendix A to this subpart, while operating the unit at the nameplate minimum input rate (i.e., part load). Calculate TE using the procedure specified in sections 3 and 4 of appendix A to this subpart.
1.6 For commercial warm air furnaces that are designed for outdoor installation (including but not limited to CWAFs that are weatherized, or approved for resistance to wind, rain, or snow), or indoor installation within an unheated space (i.e., isolated combustion systems), determine the jacket loss using Section 5.40 and Annex J of ANSI Z21.47-2021 while the unit is operating at the minimum nameplate input. Alternatively, the jacket loss determined in section 1.2 of this appendix at the maximum nameplate input may be used.
1.7 For commercial warm air furnaces that are designed only for indoor installation within a heated space, jacket loss shall be zero. For commercial warm air furnaces that are designed for indoor installation within a heated or unheated space, multiply the jacket loss determined in section 1.6 of this appendix by 1.7. For all other commercial warm air furnaces, including commercial warm air furnaces that are designed for outdoor installation (including but not limited to CWAFs that are weatherized, or approved for resistance to wind, rain, or snow), multiply the jacket loss determined in section 1.6 of this appendix by 3.3.
1.8 Subtract the jacket loss determined in section 1.7 of this appendix from the TE determined in section 1.5 of this appendix to determine the part-load efficiency.
1.9 Calculate TE2 by taking the average of the full-load and part-load efficiencies as determined in sections 1.4 and 1.8 of this appendix, respectively.