Table 403.3.2(4)

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, e	Test Procedurea
Warm air furnaces, gas fired	< 225,000 Btu/h	—	80% AFUE or 80% Etc	DOE 10 C.F.R. Part 430 or ANSI Z21.47
	≥ 225,000 Btu/h	Maximum capacityc	80% Etf	ANSI Z21.47
Warm air furnaces, oil fired	< 225,000 Btu/h	—	83% AFUE or 80% Etc	DOE 10 C.F.R. Part 430 or UL 727
	≥ 225,000 Btu/h	Maximum capacityb	81% Etg	UL 727
Warm air duct furnaces, gas fired	All capacities	Maximum capacityb	80% Ec	ANSI Z83.8
Warm air unit heaters, gas fired	All capacities	Maximum capacityb	80% Ec	ANSI Z83.8
Warm air unit heaters, oil fired	All capacities	Maximum capacityb	80% Ec	UL 731

For SI:	1 British thermal unit per hour = 0.2931 W.
a	Chapter 12 of the referenced standard contains a complete specification of the referenced test procedure, including the referenced year version of the test procedure.
b	Minimum and maximum ratings as provided for and allowed by the unit's controls.
c	Combination units not covered by the National Appliance Energy Conservation Act of 1987 (NAECA) (3-phase power or cooling capacity greater than or equal to 65,000 Btu/h [19 kW]) shall comply with either rating.

dEt	=	Thermal efficiency. See test procedure for detailed discussion.
eEc	=	Combustion efficiency (100% less flue losses). See test procedure for detailed discussion.
fEc	=	Combustion efficiency. Units must also include an IID, have jackets 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.
gEt	=	Thermal efficiency. Units must also include an 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.