Water-heating
equipment, hot-water supply boilers used solely for heating
potable water, pool heaters, and hot water storage
tanks shall comply with the criteria listed in Table L503.3.2. Where multiple criteria are listed, all criteria
shall be met. The omission of minimum performance requirements for certain classes of equipment does not
preclude the use of such equipment where appropriate.
Equipment not listed in Table L503.3.2 has no minimum
performance requirements.
For SI units: 1 gallon = 3.785 L, 1000 British thermal units per hour = 0.293 kW, °C = (°F-32)/1.8
Notes:
Exceptions: Water heaters and hot-water supply boilers
having more than 140 gallons (530 L) of storage capacity
are not required to meet the standby loss (SL) requirements
of Table L503.3.2 where:
- The tank surface is thermally insulated to R-12.5.
- A standing pilot light is not installed.
- Gas- or oil-fired storage water heaters have a flue damper or fan-assisted combustion. [ASHRAE 90.1:7.4.2]
| EQUIPMENT TYPE | SIZE CATEGORY (INPUT) | SUBCATEGORY OR RATING CONDITION | PERFORMANCE REQUIRED1 | TEST PROCEDURE2,3 |
|---|---|---|---|---|
| Electric table top water heaters | ≤12 kW | Resistance ≥20 gal | See footnote 7 | - |
| Electric water heaters | ≤12 kW5 | Resistance ≥20 gal | See footnote 7 | - |
| >12 kW5 | Resistance ≥20 gal | 0.3 + 27√Vm %/h | Section G.2 of CSA Z21.10.3 | |
| ≤24 Amps and ≤250 Volts | Heat Pump | See footnote 7 | - | |
| Gas storage water heaters | ≤75000 Btu/h | ≥20 gal | See footnote 7 | - |
| >75000 Btu/h6 | <4000 (Btu/h)/gal | 80% Et (Q/800 + 110√V) SL, Btu/h | Sections G.1 and G.2 of CSA Z21.10.3 | |
| Gas instantaneous water heaters | >50000 Btu/h and <200000 Btu/h | ≥4000 (Btu/h)/gal and <2 gal | See footnote 7 | - |
| ≥200000 Btu/h4, 6 | ≥4000 (Btu/h)/gal and <10 gal | 80% Et | Sections G.1 and G.2 of CSA Z21.10.3 | |
| ≥200000 Btu/h6 | ≥4000 (Btu/h)/gal and ≥10 gal | 80% Et (Q/799 + 16.6√V) SL, Btu/h | ||
| Oil storage water heaters | ≤105000 Btu/h | ≥20 gal | 0.59-0.0005V EF | - |
| > 105000 Btu/h | <4000 (Btu/h)/gal | 80% Et (Q/800 + 110√V) SL, Btu/h | Sections G.1 and G.2 of CSA Z21.10.3 |
|
| Oil instantaneous water heaters | ≤210000 Btu/h | ≥4000 (Btu/h)/gal and <2 gal | See footnote 7 | - |
| >210000 Btu/h | ≥4000 (Btu/h)/gal and <10 gal | 80% Et | Sections G.1 and G.2 of CSA Z21.10.3 | |
| >210000 Btu/h | ≥4000 (Btu/h)/gal and ≥10 gal | 78% Et (Q/800 + 110√V) SL, Btu/h | ||
| Hot-water supply boilers, gas and oil6 | ≥300000 Btu/h and <12500000 Btu/h | ≥4000 (Btu/h)/gal and <10 gal | 80% Et | Sections G.1 and G.2 of CSA Z21.10.3 |
| Hot-water supply boilers, gas6 | - | ≥4000 (Btu/h)/gal and ≥10 gal | 80% Et (Q/800 + 110√V) SL, Btu/h | |
| Hot-water supply boilers, oil | - | ≥4000 (Btu/h)/gal and ≥10 gal | 78% Et (Q/800 + 110√V) SL, Btu/h | |
| Pool heaters, oil and gas | All | - | See footnote 7 | ASHRAE 146 |
| Heat pump pool heaters | All | 50°F db 44.2°F wb Outdoor air 80.0°F entering water | 4.0 COP | AHRl 1160 |
| Unfired storage tanks | All | - | R-12.5 | (none) |
Notes:
- 1 Thermal efficiency (Et) is a minimum requirement, while standby loss (SL) is maximum Btu/h (kW) based on a 70°F (21 °C) temperature difference between stored water and ambient requirements. In the SL equation, V is the rated volume in gallons and Q is the nameplate input rate in Btu/h (kW). Vm is the measured volume in the tank in gallons.
- 2 ASHRAE 90.1 contains a complete specification, including the year version, of the referenced test procedure.
- 3 Section G.1 is titled "Test Method for Measuring Thermal Efficiency" and Section G.2 is titled "Test Method for Measuring Standby Loss."
- 4 Instantaneous water heaters with input rates below 200000 Btu/h (58.6 kW) shall be in accordance with these requirements where the water heater is designed to heat water to temperatures of 180°F (82°C) or higher.
- 5 Electric water heaters with input rates less than 40 946 Btu/h (12 kW) shall be in accordance with these requirements where the water heater is designed to heat water to temperatures of 180°F (82°C) or higher.
- 6 Refer to Section L503.4.3 for additional requirements for gas storage and instantaneous water heaters and gas hot water supply boilers.
- 7 In the U.S., the efficiency requirements for water heaters or gas pool heaters in this category or subcategory are specified by the U.S. Department of Energy. Those requirements and applicable test procedures are found in the Code of Federal Regulations 10 CFR Part 430.