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California Mechanical Code (Part 4, Title 24, California Code of Regulations) - page 11 / 49

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11 / 49

701.3 – 701.8

input rating of all gas utilization equipment in the space, but not less than 100 in.2 (0.06 m2). One opening shall commence within twelve (12) inches (300 mm) of the top, and one opening shall commence within twelve (12) in. (300 mm) of the bottom, of the enclosure. (See Figure 7-1.) The minimum dimension of air openings shall be not less than three (3) inches (80 mm). [NFPA 54: 9.3.2.3(1)]

(2) Combining spaces in different stories. The volumes of spaces in different stories shall be considered as communicating spaces where such spaces are connected by one or more openings in doors or floors having a total minimum free area of 2 in.2/1,000 Btu/h (4,400 mm2/kw) of total input rating of all g a s u t i l i z a t i o n e q u i p m e n t . [ N F P A 5 4 : 9 . 3 . 2 . 3 ( 2 ) ] 7 0 1 . 4 O u t d o o r C o m b u s t i o n A i r . O u t d o o r c o m b u s t i o n air shall be provided through opening(s) to the outdoors in accordance with the methods in Section 701.4.1 or 701.4.2. The minimum dimension of air openings shall not be less than three (3) inches (80 m m ) . [ N F P A 5 4 : 9 . 3 . 3 ] 7 0 1 . 4 . 1 T w o P e r m a n e n t O p e n i n g s M e t h o d . Two permanent openings, one commencing within twelve (12) inches (300 mm) of the top and one commencing within twelve (12) inches (300 mm) of the bottom of the enclosure, shall be provided. The openings shall communicate directly, or by ducts, with the outdoors or spaces that freely communicate with the outdoors, as follows [NFPA 54:9.3.3.1]:

(1) Where directly communicating with the outdoors or where communicating to the outdoors through vertical ducts, each opening shall have a minimum free area of 1 in.2/4,000 Btu/h (550 mm2/kW) of total input rating of all equipment in the enclosure. (See Figures 7-2 and 7-3.) [NFPA 54:9.3.3.1(1)]

(2) Where communicating with the outdoors through horizontal ducts, each opening shall have a minimum free area of 1 in.2/2,000 Btu/h (1,100 mm2/kW) of total input rating of all equipment in the enclosure. (See Figure 7 - 4 . ) [ N F P A 5 4 : 9 . 3 . 3 . 1 ( 2 ) ] 7 0 1 . 4 . 2 O n e P e r m a n e n t O p e n i n g M e t h o d . O n e permanent opening, commencing within twelve (12) inches (300 mm) of the top of the enclosure, shall be provided. The equipment shall have clearances of at least one (1) inch (25 mm) from the sides and back and six (6) inches (160 mm) from the front of the appliance. The opening shall directly communicate with the outdoors or shall

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2007 CALIFORNIA MECHANICAL CODE

communicate through a vertical or horizontal duct to the outdoors or spaces that freely communicate with the outdoors (see Figure 7-5) and shall have a minimum free area of [NFPA 54: 9.3.3.2]:

(1) 1 in.2/3,000 Btu/h (700 mm2/kW) of the total input rating of all equipment located in the enclosure, and

(2) Not less than the sum of the areas of all vent c o n n e c t o r s i n t h e s p a c e . [ N F P A 5 4 : 9 . 3 . 3 . 2 ] 7 0 1 . 5 C o m b i n a t i o n I n d o o r a n d O u t d o o r C o m b u s t i o n A i r . T h e u s e o f a c o m b i n a t i o n o f i n d o o r a n d o u t d o o r combustion air shall be in accordance with Sections 7 0 1 . 5 . 1 t h r o u g h 7 0 1 . 5 . 3 . [ N F P A 5 4 : 9 . 3 . 4 ] 7 0 1 . 5 . 1 I n d o o r O p e n i n g s . W h e r e u s e d , o p e n i n g s connecting the interior spaces shall comply with S e c t i o n 7 0 1 . 3 . 1 . [ N F P A 5 4 : 9 . 3 . 4 ( 1 ) ] 7 0 1 . 5 . 2 O u t d o o r o p e n i n g ( s ) s h a l l b e l o c a t e d i n accordance with Section 701.4. [NFPA 5 4 : 9 . 3 . 4 ( 2 ) ] 7 0 1 . 5 . 3 O u t d o o r O p e n i n g ( s ) S i z e . T h e o u t d o o r opening(s) size shall be calculated in accordance with the following [NFPA 54:9.3.4(3)]:

  • (1)

    The ratio of interior spaces shall be the available volume of all communicating spaces divided by the required volume. [NFPA 54:9.3.4(3)(a)]

  • (2)

    The outdoor size reduction factor shall be 1 minus the ratio of interior spaces. [NFPA 54:9.3.4(3)(b)]

(3) The minimum size of outdoor opening(s) shall be the full size of outdoor opening(s) calculated in accordance with Section 701.4, multiplied by the reduction factor. The minimum dimension of air openings shall not be less than three (3) inches (80 mm). [ N F P A 5 4 : 9 . 3 . 4 ( 3 ) ( c ) ] 7 0 1 . 6 E n g i n e e r e d I n s t a l l a t i o n s . E n g i n e e r e d combustion air installations shall provide adequate supply of combustion, ventilation, and dilution air and shall be approved by the Authority Having J u r i s d i c t i o n . [ N F P A 5 4 : 9 . 3 . 5 ] 7 0 1 . 7 M e c h a n i c a l C o m b u s t i o n A i r S u p p l y . W h e r e all combustion air is provided by a mechanical air supply system, the combustion air shall be supplied from outdoors at the minimum rate of 0.35 feet3/min per 1,000 Btu/h (0.034 m3/min per kW) for all a p p l i a n c e s l o c a t e d w i t h i n t h e s p a c e . [ N F P A 5 4 : 9 . 3 . 6 ] 7 0 1 . 8 M e c h a n i c a l C o m b u s t i o n A i r R e q u i r e m e n t s . 7 0 1 . 8 . 1 W h e r e e x h a u s t f a n s a r e i n s t a l l e d , additional air shall be provided to replace the exhausted air. [NFPA 54:9.3.6.1]

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