Raypak 302B, 902B Conventional Combustion Air Supply, TruSeal Combustion Air, U.S. Installations

three or four sheet metal screws (not supplied) equal- ly distributed around the circumference of the duct. All ducting should be self-supported. The filter housing is not designed to support the air duct.

CAUTION: Use TrueSeal combustion air if damaging airborne contaminants are or will be present in the heater area. See the Appendix regarding air contamination.

TruSeal™ Combustion Air

In certain applications it may be necessary to utilize the TruSeal option (sales order option D-21 or D-22) and duct the combustion air directly to the blower. Combustion air may be ducted directly to the heater by using PVC, CPVC or sealed single-wall galvanized ducting. The duct will attach directly to the air collar lo- cated on the side of the heater, using three or four sheet metal screws (not supplied) equally positioned around the circumference of the duct. The screws and duct connection point must be sealed with RTV (not supplied). An in-line intake air filter kit (sales order option D-17) must be installed in the combustion air duct. TruSeal is generally used when damaging con- taminants are present in the mechanical room.

TruSeal heater connection points are available as fol- lows:

302B & 402B Right side only

502B to 902B Left side - standard Right side - optional

CAUTION: This type of installation is recommended if damaging airborne contaminants are or will be present in the heater area. See the Appendix regarding air contamination.

Conventional Combustion Air Supply

U.S. Installations

All Air from Inside the Building

The confined space shall be provided with TWO per- manent openings communicating directly with an additional room(s) of sufficient volume so that the com- bined volume of all spaces meets the criteria for a room large in comparison (NFGC). The total input of all gas utilization equipment installed in the combined

space shall be considered in making this determina- tion. Each opening shall have a minimum free area of 1 in.2 per 1,000 BTUH (2,225 mm2 per kW) of the total input rating of all gas utilization equipment in the con- fined space, but not less than 100 in.2 (645 cm2). One opening shall commence within 12 in. (305 mm) of the top, and one opening shall commence within 12 in. (305 mm) of the bottom of the enclosure. The mini- mum dimension of air openings shall be not less than 3 in. (76 mm) in any direction.

All Air from Outdoors

The confined space shall communicate with the out- doors in accordance with one of the methods below. The minimum dimension of air openings shall not be less than 3 in. (76 mm) in any direction. Where ducts are used, they shall be of the same cross-sectional area as the net free area of the openings to which they connect.

1.Two permanent openings, one commencing within 12 in. (305 mm) of the top, and one com- mencing within 12 in. (305 mm) of the bottom of the enclosure, shall be provided. The openings shall communicate directly, or by ducts, with the outdoors or spaces (crawl or attic) that freely com- municate with the outdoors.

a.Where directly communicating with the out- doors or where communicating to the outdoors through vertical ducts, each opening shall have a minimum free area of 1 in.2 per 4,000 BTUH (550 mm2 per kW) of total input rating of all equipment in the enclosure.

b.Where communicating with the outdoors through horizontal ducts, each opening shall have a minimum free area of 1 in.2 per 2,000 BTUH (1,100 mm2 per kW) of total input rat- ing of all equipment in the enclosure.

2.One permanent opening, commencing within 12 in. (305 mm) of the top of the enclosure, shall be permitted where the equipment has clearances of at least 1 in. (25 mm) from the sides and back and 6 in. (152 mm) from the front of the appliance. The opening shall directly communicate with the out- doors or shall communicate through a vertical or horizontal duct to the outdoors or spaces that freely communicate with the outdoors, and shall have a minimum free area of:

a.1 in.2 per 3,000 BTUH (740 mm2 per kW) of the total input rating of all equipment located in the enclosure, and

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