§ 431.110 Energy conservation standards and their effective dates.

(a) Each commercial storage water heater, instantaneous water heater, unfired hot water storage tank and hot water supply boiler (excluding residential-duty commercial water heaters) must meet the applicable energy conservation standard level(s) as specified in the table in this paragraph. Any packaged boiler that provides service water that meets the definition of “commercial packaged boiler” in subpart E of this part, but does not meet the definition of “hot water supply boiler” in subpart G, must meet the requirements that apply to it under subpart E.

Equipment category Size Energy conservation standarda
Maximum standby lossc (equipment manufactured on and after October 29, 2003)b Minimum thermal efficiency (equipment manufactured on and after October 29, 2003 and
before October 9, 2015)b
(%) 		Minimum thermal efficiency (equipment manufactured on and after October 9, 2015)b
(%)
Electric storage water heaters All 0.30 + 27/Vm (%/hr) N/A N/A
Gas-fired storage water heaters ≤155,000 Btu/hr Q/800 + 110(Vr)1⁄2 (Btu/hr) 80 80
>155,000 Btu/hr Q/800 + 110(Vr)1⁄2 (Btu/hr) 80 80
Oil-fired storage water heaters ≤155,000 Btu/hr Q/800 + 110(Vr)1⁄2 (Btu/hr) 78 80
>155,000 Btu/hr Q/800 + 110(Vr)1⁄2 (Btu/hr) 78 80
Gas-fired instantaneous water heaters and hot water supply boilers <10 gal
≥10 gal		 N/A
Q/800 + 110(Vr)1⁄2 (Btu/hr)		 80
80		 80
80
Oil-fired instantaneous water heaters and hot water supply boilers <10 gal
≥10 gal		 N/A
Q/800 + 110(Vr)1⁄2 (Btu/hr)		 80
78		 80
78
Equipment category Size Minimum thermal insulation
Unfired hot water storage tank All R-12.5

a Vm is the measured storage volume (in gallons), and Vr is the rated volume (in gallons). Q is the nameplate input rate in Btu/hr.

b For hot water supply boilers with a capacity of less than 10 gallons: (1) The standards are mandatory for products manufactured on and after October 21, 2005, and (2) products manufactured prior to that date, and on or after October 23, 2003, must meet either the standards listed in this table or the applicable standards in subpart E of this part for a “commercial packaged boiler.”

c Water heaters and hot water supply boilers having more than 140 gallons of storage capacity need not meet the standby loss requirement if: (1) The tank surface area is thermally insulated to R-12.5 or more; (2) a standing pilot light is not used; and (3) for gas or oil-fired storage water heaters, they have a fire damper or fan-assisted combustion.

(b) Each residential-duty commercial water heater must meet the applicable energy conservation standard level(s) as follows:

Product class Specificationsa Draw pattern Uniform energy factorb
Gas-fired Storage >75 kBtu/hr and ≤105 kBtu/hr and ≤120 gal Very Small
Low		 0.2674 − (0.0009 × Vr)
0.5362 − (0.0012 × Vr)
Medium 0.6002 − (0.0011 × Vr)
High 0.6597 − (0.0009 × Vr)
Oil-fired Storage >105 kBtu/hr and ≤140 kBtu/hr and ≤120 gal Very Small
Low		 0.2932 − (0.0015 × Vr)
0.5596 − (0.0018 × Vr)
Medium 0.6194 − (0.0016 × Vr)
High 0.6740 − (0.0013 × Vr)
Electric Instantaneous >12 kW and ≤58.6 kW and ≤2 gal Very Small 0.80
Low 0.80
Medium 0.80
High 0.80

a Additionally, to be classified as a residential-duty commercial water heater, a commercial water heater must meet the following conditions: (1) if the water heater requires electricity, it must use a single-phase external power supply; and (2) the water heater must not be designed to heat water to temperatures greater than 180 °F.

b Vr is the rated storage volume (in gallons), as determined pursuant to 10 CFR 429.44.

[81 FR 96238, Dec. 29, 2016]