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California Mechanical Code (Part 4, Title 24, California Code of Regulations) - page 12 / 49

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CHIMNEYS AND VENTS

vent diameter shall be used to determine the minimum vent capacity, and the connector diameter shall be used to determine the maximum vent capacity. The flow area of the vertical vent shall not exceed seven times the flow area of the listed appliance categorized vent area, flue collar area, or draft hood outlet area unless designed in accordance with approved e n g i n e e r i n g m e t h o d s . 8 0 3 . 1 . 8 C o n n e c t i o n t o C h i m n e y L i n e r s . C o n n e c t i o n s b e t w e e n c h i m n e y l i n e r s a n d l i s t e d double-wall connectors shall be made with listed adapters designed for such purpose. [NFPA 5 4 : 1 3 . 1 . 8 ] 8 0 3 . 1 . 8 . 1 T a b l e s 8 - 5 t h r o u g h 8 - 9 s h a l l b e used for chimneys and vents not exposed to the outdoors below the roof line. A Type B vent or listed chimney lining system passing through an unused masonry chimney flue shall not be considered to be exposed to the outdoors. A Type B vent passing through an unventilated enclosure or chase insulated to a value of not less than R8 shall not be considered to be exposed to the outdoors. Table 8-7 in combination with Table 8-15 shall be used for clay-tile-lined exterior masonry chimneys, provided all of the following are met:

  • (1)

    The vent connector is Type B double wall.

  • (2)

    The vent connector length is limited to 1-1/2 feet for each inch (180 mm/mm) of vent connector diameter.

  • (3)

    The appliance is draft hood equipped.

  • (4)

    The input rating is less than the maximum capacity given in Table 8-7.

  • (5)

    For a water heater, the outdoor design temperature shall not be less than 5°F (–15°C).

  • (6)

    For a space-heating appliance, the input rating is greater than the minimum capacity given by Table 8-15.

  • (7)

    Where the conditions of 803.1.8.1(1) through (6) cannot be met, an alternative venting design shall be used, such as a listed chimney lining system.

Exception: Vents serving listed appliances installed in accordance with the appliance manufacturer’s instructions and the t e r m s o f t h e l i s t i n g . 8 0 3 . 1 . 9 C o r r u g a t e d v e n t c o n n e c t o r s s h a l l n o t b e smaller than the listed appliance categorized vent diameter, flue collar diameter, or draft hood outlet diameter.

803.1 – 803.2

8 0 3 . 1 . 9 . 1 V e r t i c a l V e n t U p s i z i n g / 7 T i m e s R u l e . W h e r e t h e v e r t i c a l v e n t h a s a l a r g e r diameter than the vent connector, the vertical vent diameter shall be used to determine the minimum vent capacity, and the connector diameter shall be used to determine the maximum vent capacity. The flow area of the vertical vent shall not exceed seven times the flow area of the listed appliance categorized vent area, flue collar area, or draft hood outlet area unless designed in accordance with approved e n g i n e e r i n g m e t h o d s . [ N F P A 5 4 : 1 3 . 1 . 9 ] 8 0 3 . 1 . 1 0 V e n t c o n n e c t o r s s h a l l n o t b e u p s i z e d more than two sizes greater than the listed appliance categorized vent diameter, flue collar d i a m e t e r , o r d r a f t h o o d o u t l e t d i a m e t e r . 8 0 3 . 1 . 1 1 I n a s i n g l e r u n o f v e n t o r v e n t c o n n e c - tor, more than one diameter and type shall be permitted to be used, provided that all the sizes a n d t y p e s a r e p e r m i t t e d b y t h e t a b l e s . 8 0 3 . 1 . 1 2 I n t e r p o l a t i o n s h a l l b e p e r m i t t e d i n calculating capacities for vent dimensions that fall between table entries. (See Example 8-1 in S e c t i o n 8 0 3 . 2 . 2 3 . ) 8 0 3 . 1 . 1 3 E x t r a p o l a t i o n b e y o n d t h e t a b l e e n t r i e s shall not be permitted.

For SI units, 1 in. = 25.4 mm; 1 ft. = 0.305 m; 1 , 0 0 0 B t u / h = 0 . 2 9 3 k W ; 1 i n . 2 = 6 4 5 m m 2 . 8 0 3 . 1 . 1 4 F o r v e n t h e i g h t s l o w e r t h a n s i x ( 6 ) f e e t and higher than shown in the tables, engineering methods shall be used to calculate vent capacities. [ N F P A 5 4 : 1 3 . 1 ] 8 0 3 . 1 . 1 5 D r a f t H o o d C o n v e r s i o n A c c e s s o r i e s . Draft hood conversion accessories for use with masonry chimneys venting listed Category I fan- assisted appliances shall be listed and installed in accordance with the listed accessory manufac- t u r e r s i n s t a l l a t i o n i n s t r u c t i o n s . [ N F P A 5 4 : 1 3 . 1 . 1 0 ] 8 0 3 . 2 A d d i t i o n a l R e q u i r e m e n t s t o M u l t i p l e A p p l i a n c e V e n t T a b l e s 8 - 1 0 t h r o u g h 8 - 1 4 a n d T a b l e s 8 - 1 6 t h r o u g h 8 - 1 9 . 8 0 3 . 2 . 1 T h e s e v e n t i n g t a b l e s s h a l l n o t b e u s e d where obstructions (see Section 802.15) are installed in the venting system. The installation of vents serving listed appliances with vent dampers shall be in accordance with the appliance manufacturer’s instructions or in accordance with the following:

(1) The maximum capacity of the vent connector shall be determined using the NAT Max column.

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