Raypak 122-322 Combustion and Ventilation Air, Conventional Combustion Air Supply, Indoor Units

These clearances are required when the outdoor vent cap is used. If installing the heater outdoors with a vent stack, the indoor clearances may be utilized.

The combustion air intake hood MUST be used for outdoor installations. The hood is shipped loose and installed on the side of the heater over the filter box at the job site.

Combustion and Ventilation Air

Indoor Units

The heater must be supplied with sufficient quantities of non-contaminated air to support proper combustion and equipment ventilation. Combustion air can be sup- plied via conventional means where combustion air is drawn from the area immediately surrounding the heater, or via direct vent, where combustion air is drawn directly from outside. All installations must com- ply with the requirements of the NFGC (U.S.) and B149 (Canada), and all local codes.

CAUTION: Combustion air must not be contaminated by corrosive chemical fumes which can damage the heater and void the warranty. (See the Appendix.)

Direct Combustion Air

If outside air is drawn through the intake pipe directly to the unit for combustion:

1.Install combustion air direct vent in accordance with the venting section of this manual.

2.Provide adequate ventilation of the space occu- pied by the heater(s) by an opening(s) for ventilation air at the highest practical point com- municating with the outdoors. The total cross-sectional area shall be at least 1 in.2 of free area per 20,000 BTUH (111 mm2 per kW) of total input rating of all equipment in the room when the opening is communicating directly with the out- doors or through vertical duct(s). The total cross-sectional area shall be at least 1 in.2 of free area per 10,000 BTUH (222 mm2 per kW) of total input rating of all equipment in the room when the opening is communicating with the outdoors through horizontal duct(s).

3.In cold climates, and to mitigate potential freeze- up, Raypak highly recommends the installation of

a motorized sealed damper to prevent the circula- tion of cold air through the heater during the non-operating hours.

Conventional Combustion Air Supply

U.S. Installations

All Air from Inside the Building

The confined space shall be provided with two perma- nent openings communicating directly with an additional room(s) of sufficient volume so that the com- bined volume of all spaces meets the criteria for an unconfined space. The total input of all gas utilization equipment installed in the combined space shall be considered in making this determination. Each open- ing shall have a minimum free area of 1 square inch per 1,000 Btu per hour (22 cm² 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. (30 cm) of the top, and one opening shall commence within 12 in. (30 cm) of the bottom, of the enclosure. The minimum dimension of air openings shall be not less than 3 in. (8 cm) in any direction.

All Air from Outdoors

The confined space shall communicate with the out- doors in accordance with methods 1 or 2. The minimum dimension of air openings shall not be less than 3 in. (8 cm) in any direction. Where ducts are used, they shall be of the same cross-sectional area as the free area of the openings to which they connect.

1.Two permanent openings, one commencing with- in 12 in. (30 cm) of the top, and one commencing within 12 in. (30 cm) of the bottom, of the enclo- sure shall be provided. The openings shall communicate directly, or by ducts, with the out- doors or spaces (crawl or attic) that freely communicate 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 sq in. per 4000 Btu per hr (5.5 cm2 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 sq in. per 2000

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