Raypak 399B-2339B Installation & Operating Instructions Manual

space shall be considered in making this determina-tion. Each opening shall have a minimum free area of1 in. 2 per 1,000 BTUH (2,225 mm 2 per kW) of the totalinput rating of all gas utilization equipment in the con-fined space, but not less than 100 in. 2 (645 cm 2 ). Oneopening shall commence within 12 in. (305 mm) of thetop, 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 than3 in. (76 mm) in any direction.All Air from OutdoorsThe confined space shall communicate with the out-doors in accordance with one of the methods below.The minimum dimension of air openings shall not beless than 3 in. (76 mm) in any direction. Where ductsare used, they shall be of the same cross-sectionalarea as the net free area of the openings to which theyconnect.1. Two permanent openings, one commencingwithin 12 in. (305 mm) of the top, and one com-mencing within 12 in. (305 mm) of the bottom ofthe enclosure, shall be provided. The openingsshall communicate directly, or by ducts, with theoutdoors or spaces (crawl or attic) that freely com-municate with the outdoors.a. Where directly communicating with the out-doors or where communicating to theoutdoors through vertical ducts, each openingshall have a minimum free area of 1 in. 2 per4,000 BTUH (550 mm 2 per kW) of total inputrating of all equipment in the enclosure.b. Where communicating with the outdoorsthrough horizontal ducts, each opening shallhave a minimum free area of 1 in. 2 per 2,000BTUH (1,100 mm 2 per kW) of total input rat-ing of all equipment in the enclosure.2. One permanent opening, commencing within 12in. (305 mm) of the top of the enclosure, shall bepermitted where the equipment has clearances ofat least 1 in. (25 mm) from the sides and back and6 in. (152 mm) from the front of the appliance. Theopening shall directly communicate with the out-doors or shall communicate through a vertical orhorizontal duct to the outdoors or spaces thatfreely communicate with the outdoors, and shallhave a minimum free area of:a. 1 in. 2 per 3,000 BTUH (740 mm 2 per kW) ofthe total input rating of all equipment located inthe enclosure, andb. Not less than the sum of the areas of all ventconnectors in the confined space.WARNING: Do not use one permanent openingmethod if the equipment room is under negativepressure conditions or the equipment is commonvented with other gas-fired appliances.1. Ventilation of the space occupied by the heatershall be provided by an opening(s) for ventilationair at the highest practical point communicatingwith the outdoors. The total cross-sectional area ofsuch an opening(s) shall be at least 10% of thearea required in 2. and 3. (below), but in no caseshall the cross-sectional area be less than 10 in. 2(65 cm 2 ).2. For heaters using a barometric damper in the ventsystem there shall be a permanent air supplyopening(s) having a cross section area of not lessthan 1 in. 2 per 7,000 BTUH (320 mm 2 per kW) upto and including 1 million BTUH, plus 1 in. 2 per14,000 BTUH (160 mm 2 per kW) in excess of 1million BTUH. This opening(s) shall be eitherlocated at or ducted to a point not more than 18 in.(450 mm) nor less than 6 in. (152 mm) above thefloor level. The duct can also “goose neck” throughthe roof. The duct is preferred to be straight downand terminated 18 in. (450 mm) from the floor, butnot near piping. This air supply opening require-ment shall be in addition to the air opening forventilation air required in 1. (above).3. For heaters not using a barometric damper in thevent system, and when air supply is provided bynatural air flow from outdoors for a power burnerand there is no draft regulator, drafthood or similarflue gas dilution device installed in the samespace, in addition to the opening for ventilation airrequired in 1., there shall be a permanent air sup-ply opening(s) having a total cross-sectional areaCAUTION: All combustion air must be drawn fromthe air outside of the building; the mechanical equip-ment room must communicate directly with theoutdoors.Canadian InstallationsWARNING: Care must be taken to ensure that theequipment room is not under negative pressureconditions or that the equipment is not common-vented with other gas-fired appliances.13