PDFWAC 51-11C-403325
Table C403.3.2(5)—Minimum efficiency requirements—Warm air furnaces and unit heaters.
Table C403.3.2(5)
Warm Air Furnaces and Combination Warm Air Furnaces/Air-Conditioning Units, Warm Air Duct Furnaces and Unit Heaters—Minimum Efficiency Requirements
Equipment Type | Size Category (Input) | Subcategory or Rating Condition | Minimum Efficiencyd,c | Test Procedurea |
Warm-air furnace, gas fired for application outside the U.S. | < 225,000 Btu/h | Maximum capacityc | 80% AFUE (nonweatherized) or 1% AFUE (weatherized) or 80% Etb,d | DOE 10 C.F.R. 430 Appendix N or Section 2.39, Thermal Efficiency, ANSI Z21.47 |
Warm-air furnace, gas fired | < 225,000 Btu/h | Maximum capacityc | 80% Etb,d before 1/1/2023 81% Etd after 1/1/2023 | Section 2.39, Thermal Efficiency, ANSI Z21.47 |
Warm-air furnace, oil fired | < 225,000 Btu/h | Maximum capacityc | 83% AFUE (nonweatherized) or 78% AFUE (weatherized) or 80% Etb,d | DOE 10 C.F.R. 430 Appendix N or Section 42, Combustion UL 727 |
Warm-air furnace, oil fired | < 225,000 Btu/h | Maximum capacityc | 80% Et before 1/1/2023 82% Etd after 1/1/2023 | Section 42, Combustion UL 727 |
Electric furnaces for applications outside the U.S. | < 225,000 Btu/h | All | 96% AFUE | DOE 10 C.F.R. 430 Appendix N |
Warm air duct furnaces, gas fired | All capacities | Maximum capacityc | 80% Ece | Section 2.10, Efficiency, ANSI Z83.8 |
Warm air unit heaters, gas fired | All capacities | Maximum capacityc | 80% Ece,f | Section 2.10, Efficiency, ANSI Z83.8 |
Warm air unit heaters, oil fired | All capacities | Maximum capacityc | 80% Ece,f | Section 40, Combustion, UL 731 |
For SI: 1 British thermal unit per hour = 0.2931 W. | ||||
a | Chapter 6 contains a complete specification of the referenced standards, which include test procedures, including the referenced year version of the test procedure. | |||
b | Combination units (i.e., furnaces contained within the same cabinet as an air conditioner) not covered by DOE 10 C.F.R. 430 (i.e., 3-phase power or with cooling capacity greater than or equal to 65,000 Btu/h) may comply with either rating. All other units greater than 225,000 Btu/h sold in the U.S. must meet the AFUE standards for consumer products and testing using U.S. DOE's AFUE test procedure at DOE 10 C.F.R. 430 Subpart B, Appendix N. | |||
c | Compliance of multiple firing rate units shall be at the maximum firing rate. | |||
d | Et | = | Thermal efficiency. Units must also include an interrupted or intermittent ignition device (IID), have jacket losses not exceeding 0.75 percent of the input rating, and have either power venting or a flue damper. A vent damper is an acceptable alternative to a flue damper for those furnaces where combustion air is drawn from the conditioned space. | |
e | Ec | = | Combustion efficiency (100% less flue losses). See test procedure for detailed discussion. | |
f | Units must also include an interrupted or intermittent ignition device (IID) and have either power venting or an automatic flue damper. | |||
g | This table is a replica of ASHRAE 90.1 Table 6.8.1-5 Warm-Air Furnaces and Combination Warm-Air Furnaces/Air-Conditioning Units, Warm-Air Duct Furnaces, and Unit Heaters—Minimum Efficiency Requirements. | |||
[Statutory Authority: RCW 19.27A.020, 19.27A.025, 19.27A.160 and chapters 19.27A and 19.27 RCW. WSR 22-14-091, 23-12-101, and 23-20-021, § 51-11C-403325, filed 7/1/22, 6/7/23, and 9/25/23, effective 3/15/24.]