Index
Air Opening Requirements
(a)EQUIPMENT LOCATED IN CONFINED SPACES; ALL AIR FROM INSIDE THE BUILDING.
Two permanent openings (top and bottom) shall be provided connecting the confined space (e.g., closet/small room) with the unconfined space. Each opening shall have a free area of one square inch per 1,000 BTU/hour (22 cm²/kW) input of all appliances in the confined space, but not less than 100 square inches (645 cm²).
b)BASEMENT INSTALLATION, EQUIPMENT LOCATED IN CON- FINED SPACES; ALL AIR FROM OUTDOORS.
Outside air inlets shall be a minimum of 12” (300mm) above the grade (snow) line. When supplying air directly from the outdoors:
For American installations: Two openings (top and bottom) shall be provided with each opening having a minimum free area of one square inch per 4,000 BTU/hour input (5.5 cm²/kW) of total input rating of all appliances in the confined space.
For Canadian installations: Canadian codes specify single air supply source. Canadian customers and authorities having jurisdiction may use the sizing listed in Table 1. When using a single air supply, the duct shall terminate within 1 foot (300 mm) above and within 2 feet (600 mm) hori- zontally from the burner level of the appliance having the largest input.
Table 1
Combined input of all | Required | Acceptable Equivalent duct | |
appliances in | free area of | diameter | |
confined space | duct | A1 | B2 |
BTU/hr(kW) | in2(mm2) | in(mm) | in(mm) |
75,000(23) | 11(7,000) | 4(100) | 5(125) |
100,000(30) | 14(9,000) | 4(100) | 5(125) |
125,000(37) | 18(12,000) | 5(125) | 6(150) |
150,000(45) | 22(14,000) | 5(125) | 6(150) |
175,000(53) | 25(16,000) | 6(150) | 7(175) |
200,000(60) | 29(19,000) | 6(150) | 7(175) |
225,000(68) | 32(21,000) | 6(150) | 7(175) |
250,000(75) | 36(23,000) | 7(175) | 8(200) |
275,000(83) | 40(26,000) | 7(175) | 8(200) |
300,000(90) | 43(28,000) | 7(175) | 8(200) |
325,000(98) | 47(30,000) | 8(200) | 9(225) |
350,000(105) | 50(32,000) | 8(200) | 9(225) |
375,000(113) | 54(35,000) | 8(200) | 9(225) |
400,000(120) | 58(37,000) | 9(225) | 10(250) |
Notes:
1.Maximum lenght of ducts in column A is 20 equivalent feet(6.1 meters). 2.Maximum lenght of ducts in column B is 50 equivalent feet(15.2 meters).
(c)EQUIPMENT LOCATED IN CONFINED SPACES; ALL AIR FROM OUTDOORS.
For American installations: When supplying air directly from the out- doors using horizontal ducting, each opening shall have a free minimum area of one square inch per 2,000 BTU/hour (11 cm²/kW) of total input rating of all appliances in the confined space.
For Canadian installations: Refer to Table 1 of part (b).
(d)EQUIPMENT LOCATED IN CONFINED SPACES; ALL AIR FROM OUTDOORS THROUGH VENTILATED ATTIC.
For American installations: When supplying air directly through vertical ducting, each opening shall have a free minimum area of one square inch per 4,000 BTU/hour (5.5 cm²/kW) of total input rating of all appli- ances in the confined space.
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Figure: 2 Equipment Location
and Combustion/Ventilation Air
Requirements
(a)
Permanent |
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Ventilation |
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Air |
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Combustion
Air Duct
12”
(b)
Venting
Outdoor
Air Ducts
Combustion
(c)
Outlet Air
Inlet
Air Ducts
(d)
*U.S. installations require a dual duct system.
