506.3 Indoor Opening Size and Location. Openings

used to connect indoor spaces shall be sized and located in accordance with the following: (1) Each opening shall have a free area of not less than 1

square inch per 1000 Btu/h (0.002 m ² /kW) of the total

Each opening shall have a free area of not less than 1

square inch per 1000 Btu/h (0.002 m ² /kW) of the total input rating of appliances in the space, but not less than 100 square inches (0.065 m ² ). One opening shall commence within 12 inches (305 mm) of the top of the enclosure, and one opening shall commence within 12 inches (305 mm) of the bottom of the enclosure (see Figure 506.3). The dimension of air openings shall be not less than 3 inches (76 mm).

FIGURE 506.3 COMBUSTION AIR FROM ADJACENT INDOOR SPACES

THROUGH INDOOR COMBUSTION AIR OPENINGS

[NFPA 54: FIGURE A.9.3.2.3(1)]

(2) Where communicating with the outdoors through

horizontal ducts, each opening shall have a minimum free area of 1 square inch per 2000 Btu/h (0.001 m ² /kW) of total input rating of all appliances in the enclosure. [See Figure 506.4.1(3)] [NFPA 54:9.3.3.1]

2019 CALIFORNIA PLUMBING CODE 83

WATER HEATERS any other purpose or distributed to any other persons or parti es.

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FIGURE 506.4.1(1) COMBUSTION AIR FROM OUTDOORS INLET AIR FROM VENTILATED CRAWL SPACE AND

OUTLET AIR TO VENTILATED ATTIC

[NFPA 54: FIGURE A.9.3.3.1(1)(a)]

FIGURE 506.4.1(2) COMBUSTION AIR FROM OUTDOORS

THROUGH VENTILATED ATTIC

[NFPA 54: FIGURE A.9.3.3.1(1)(b)]

FIGURE 506.4.1(3) COMBUSTION AIR FROM OUTDOORS THROUGH HORIZONTAL DUCTS

[NFPA 54: FIGURE A.9.3.3.1(2)]

FIGURE 506.4.2 COMBUSTION AIR FROM OUTDOORS THROUGH

SINGLE COMBUSTION AIR OPENING

[NFPA 54: FIGURE A.9.3.3.2]

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84 2019 CALIFORNIA PLUMBING CODE

WATER HEATERS

506.4.2 One Permanent Opening Method. One permanent opening, commencing within 12 inches (305 mm) of the top of the enclosure, shall be provided. The appliance shall have clearances of at least 1 inch (25.4 mm) from the sides and back and 6 inches (152 mm) from the front of the appliance. The opening shall directly communicate with the outdoors or shall communicate through a vertical or horizontal duct to the outdoors or spaces that freely communicate with the outdoors (see Figure 506.4.2) and shall have a minimum free area of the following:

(1) One square inch per 3000 Btu/h (0.0007 m ² /kW) of

the total input rating of all appliances located in the

(1) One square inch per 3000 Btu/h (0.0007 m ² /kW) of

the total input rating of all appliances located in the enclosure. (2) Not less than the sum of the areas of all vent con nectors in the space. [NFPA 54:9.3.3.2]

506.7.3 Specified Combustion Air. Where combustion air is provided by the building’s mechanical ventilation system, the system shall provide the specified combustion air rate in addition to the required ventilation air. [NFPA 54:9.3.6.3]