506.2 Indoor Combustion Air. The required volume of

indoor air shall be determined in accordance with the method in Section 506.2.1 or Section 506.2.2, except that where the air infiltration rate is known to be less than 0.40 ACH (air change per hour), the method in Section 506.2.2 shall be used.

505.4.1 Single-Wall Heat Exchanger. An indirectfired water heater that incorporates a single-wall heat exchanger shall be in accordance with the following requirements: (1) The heat transfer medium shall be either potable

water or contain fluids recognized as safe by the

(1) The heat transfer medium shall be either potable

water or contain fluids recognized as safe by the Food and Drug Administration (FDA) as food grade. (2) Bear a label with the word “Caution,” followed by

the following statements:

Bear a label with the word “Caution,” followed by

the following statements: (a) The heat-transfer medium shall be potable

water or other nontoxic fluid recognized as safe

(a) The heat-transfer medium shall be potable

water or other nontoxic fluid recognized as safe by the FDA. (b) The maximum operating pressure of the heat

exchanger shall not exceed the maximum oper

(b) The maximum operating pressure of the heat

exchanger shall not exceed the maximum operating pressure of the potable water supply. (3) The word “Caution” and the statements in letters

shall have an uppercase height of not less than 0.120

The word “Caution” and the statements in letters

shall have an uppercase height of not less than 0.120 of an inch (3.048 mm). The vertical spacing between lines of type shall be not less than 0.046 of an inch (1.168 mm). Lowercase letters shall be compatible with the uppercase letter size specification.

82 2019 CALIFORNIA PLUMBING CODE

WATER HEATERS

The total required volume shall be the sum of the required volume calculated for all appliances located within the space. Rooms communicating directly with the space in which the appliances are installed through openings not furnished with doors, and through combustion air openings sized and located in accordance with Section 506.3 are considered a part of the required volume. [NFPA 54:9.3.2]

(2) The volumes of spaces in different stories shall be con sidered as communicating spaces where such spaces are

506.2.1 Standard Method. The required volume shall be not less than 50 cubic feet per 1000 British thermal units per hour (Btu/h) (4.83 m ³ /kW). [NFPA 54:9.3.2.1] 506.2.2 Known Air Infiltration Rate Method. Where the air infiltration rate of a structure is known, the minimum required volume shall be determined as follows: [NFPA 54:9.3.2.2]: (1) For appliances other than fan-assisted, calculate

using the following Equation 506.2.2(1). [NFPA

(2) The volumes of spaces in different stories shall be con sidered as communicating spaces where such spaces are connected by one or more openings in doors or floors having a total free area of not less than 2 square inches per 1000 Btu/h (0.004 m ² /kW) of total input rating of appliances. [NFPA 54:9.3.2.3]