Storage water heaters, electric

≤ 12 kWd

Resistance

DOE 10 C.F.R. Part 430

≤ 24 amps and ≤ 250 volts

Heat pump

DOE 10 C.F.R. Part 430

˃ 12 kWd

Resistance

(0.3 + 27/Vm,%/h

Section G.2 of ANSI Z21.10.3

Instantaneous water heaters, electric

All

Resistance

0.93 - 0.00132V, EF

DOE 10 C.F.R. Part 430

Storage water heaters, gas

≤ 75,000 Btu/h

≥ 20 gal

0.67 - 0.0019V, EF

DOE 10 C.F.R. Part 430

˃ 75,000 Btu/h

< 4,000 Btu/h/gal

80% Et (Q/800 + 110√V) SL, Btu/h

Section G.1 and G.2 of ANSI Z21.10.3

 

˃ 50,000 Btu/h and

< 200,000 Btu/h

≥ 4,000 (Btu/h)/gal and < 2 gal

0.62 - 0.0019V, EF

DOE 10 C.F.R. Part 430

Instantaneous water heaters, gas

≥ 200,000 Btu/hc

≥ 4,000 Btu/h/gal and < 10 gal

80% Et

Section G.1 and G.2 of ANSI Z21.10.3

 

≥ 200,000 Btu/h

≥ 4,000 Btu/h/gal and ≥ 10 gal

80% Et (Q/800 + 110√V) SL, Btu/h

Storage water heaters, oil

≤ 105,000 Btu/h

≥ 20 gal

0.59 - 0.0019V, EF

DOE 10 C.F.R. Part 430

 

˃ 105,000 Btu/h

< 4,000 Btu/h/gal

78% Et (Q/800 + 110√V) SL, Btu/h

Section G.1 and G.2 of ANSI Z21.10.3

 

≤ 210,000 Btu/h

≥ 4,000 Btu/h/gal and < 2 gal

0.59 - 0.0019V, EF

DOE 10 C.F.R. Part 430

Instantaneous water heaters, oil

˃ 210,000 Btu/h

≥ 4,000 Btu/h/gal and < 10 gal

80% Et

Section G.1 and G.2 of ANSI Z21.10.3

 

˃ 210,000 Btu/h

≥ 4,000 Btu/h/gal and ≥ 10 gal

78% Et (Q/800 + 110√V) SL, Btu/h

Hot water supply boilers, gas and oil

≥ 300,000 Btu/h and

< 12,500,000 Btu/h

≥ 4,000 Btu/h/gal and < 10 gal

80% Et

Section G.1 and G.2 of ANSI Z21.10.3

Hot water supply boilers, gas

≥ 300,000 Btu/h and

< 12,500,000 Btu/h

≥ 4,000 Btu/h/gal and ≥ 10 gal

80% Et (Q/800 + 110√V) SL, Btu/h

Hot water supply boilers, oil

≥ 300,000 Btu/h and

< 12,500,000 Btu/h

≥ 4,000 Btu/h/gal and ˃ 10 gal

78% Et (Q/800 + 110√V) SL, Btu/h

Pool heaters, gas and oil

All

—

78% Et

ASHRAE 146

Heat pump pool heaters

All

—

4.0 COP

AHRI 146

Unfired storage tanks

All

—

Minimum insulation requirement R-12.5 (h • ft2 • °F)/Btu

(none)

For SI:

°C = [(°F) - 32]/1.8, 1 British thermal unit per hour =  0.2931 W, 1 gallon =  3.785 L, 1 British thermal unit per hour per gallon =  0.078 W/L.

Energy factor (EF) and thermal efficiency (Et) are minimum requirements. In the EF equation, V is the rated volume in gallons.

Standby loss (SL) is the maximum Btu/h based on a nominal 70°F temperature difference between stored water and ambient requirements. In the SL equation, Q is the nameplate input rate in Btu/h. In the SL equation for electric water heaters, V is the rated volume in gallons and Vm is the measured volume in gallons. In the SL equation for oil and gas water heaters and boilers, V is the rated volume in gallons.

Instantaneous water heaters with input rates below 200,000 Btu/h shall comply with these requirements if the water heater is designed to heat water to temperatures 180°F or higher.

Electric water heaters with an input rating of 12 kW (40,950 Btu/h) or less that are designed to heat water to temperatures of 180°F or greater shall comply with the requirements for electric water heaters that have an input rating greater than 12 kW (40,950 Btu/h).