7.5.1 Space Heating and Service Water Heating
The use of a gas-fired or oil-fired space-heating boiler system otherwise complying with Section 6 to provide the total space heating and service water heating for a building is allowed when one of the following conditions is met:
- The single space-heating boiler, or the component of a modular or multiple boiler system that is heating the service water, has a standby loss in Btu/h not exceeding
(13.3 × pmd + 400)/n
where pmd is the probable maximum demand in gal/h determined in accordance with the procedures described in generally accepted engineering standards and handbooks, and n is the fraction of the year when the outdoor daily mean temperature is greater than 64.9°F.
The standby loss is to be determined for a test period of 24 hours duration while maintaining a boiler water temperature of at least 90°F above ambient, with an ambient temperature between 60°F and 90°F. For a boiler with a modulating burner, this test shall be conducted at the lowest input.
- It is demonstrated to the satisfaction of the authority having jurisdiction that the use of a single heat source will consume less energy than separate units.
- The energy input of the combined boiler and water heater system is less than 150,000 Btu/h.