John Wood Commercial - AJWS - Manual (Page 7)

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 CONFINED
SPACES; ALL AIR FROM OUTDOORS.
Outside air inlets shall be a minimum of 305mm (12 in) above the grade
(snow) line. When supplying air directly from the outdoors:
For American installations: Two openings (top and bottom) shall be pro-
vided 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 305mm (12 in) above and within 610mm (24 in) horizon-
tally from the burner level of the appliance having the largest input.
(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 rat-
ing 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 appliances in
the confined space.
7
Combustion
Air Duct
Permanent
Ventilation
Air
12” Grade
12”
Outdoor
Air Ducts
Venting
Combustion
Inlet
Air Ducts
Outlet Air
(a)
(b)
(d)
(c)
Figure 2: Equipment Location and
Combustion/Ventilation Air
Requirements
*U.S. installations require a dual duct system.
A
1
B
2
BTU/h (kW) mm2 (in2) mm (in) mm (in)
75,000 (23) 7,000 (11) 100 (4) 125 (5)
100,000 (30) 9,000 (14) 100 (4) 125 (5)
125,000 (37) 12,000 (18) 125 (5) 150 (6)
150,000 (45) 14,000 (22) 125 (5) 150 (6)
175,000 (53) 16,000 (25) 150 (6) 175 (7)
200,000 (60) 19,000 (29) 150 (6) 175 (7)
225,000 (68) 21,000 (32) 150 (6) 175 (7)
250,000 (75) 23,000 (36) 175 (7) 200 (8)
275,000 (83) 26,000 (40) 175 (7) 200 (8)
300,000 (90) 28,000 (43) 175 (7) 200 (8)
325,000 (98) 30,000 (47) 200 (8) 225 (9)
350,000 (105) 32,000 (50) 200 (8) 225 (9)
375,000 (113) 35,000 (54) 200 (8) 225 (9)
400,000 (120) 37,000 (58) 225 (9) 250 (10)
Com bined input of
all appliances in
confined space
Required free
area of duct
Acceptable equivalent
duct diam eter
Table 1
Notes:
1. Maximum length of ducts in column A is 6.1 equivalent metres (20 ft).
2. Maximum length of ducts in column B is 15.2 equivalent metres (50 ft).
305mm
(12 in)
305mm
(12 in)