This Standard describes the test procedures required to perform a 24 h simulated use test. This Standard also provides the calculations required to determine the first-hour rating, recovery efficiency, standby loss, daily water heating energy consumption, energy factor, and annual energy consumption for gas-fired storage water heaters.
This Standard applies to gas-fired storage water heaters
(a) with volumes not less than 20 US gal (76 L) nor more than 100 US gal (380 L);
(b) having rated inputs of 75 000 Btu/h (21.98 kW) or less; and
(c) designed to heat and store water at a thermostatically controlled temperature of less than 180°F (82 °C).
The tests contained in this Standard provide a standardized method of comparing performance and efficiency.
This Standard is written in US Customary units. The SI (metric) values given in parentheses are for information only. SI (metric) equivalents may be approximate; the mandatory requirements of this Standard are those expressed in US Customary units. The values are from the US Department of Energy publication 10 CFR, Part 430, Subpart B, Appendix E.