John Wood Commercial - AJWSC - Manual (Page 10)

Louvers and Grills
Openings for air supply ducts must provide free unobstruct-
ed air movement. Louver and grill openings must be sized
to ensure that the FREE OPEN AREA is never less than the
area of the air duct.
LOCATION:
The locations for top and bottom openings are as follows:
For Canadian installations: The top opening shall be
located as close to the ceiling as practical but never lower
than the relief opening of the lowest draft control device.
The bottom opening shall be located neither more than
457mm (18 in.), nor less than 152mm (6 in.), above floor
level.
For U.S. A. installations: The top opening shall commence
within 305mm (12 in.) of the top of space and the bottom
opening shall commence within 305mm (12 in.) of the bot-
tom of the enclosure.
Air Opening Requirements
(a) Equipment located in confined spaces; all air
from inside the building.
Two permanent openings (top and bottom) shall be pro-
vided 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 direct-
ly from the outdoors:
For Canadian installations: Canadian codes specify
single air supply source. Canadian customers and
authorities having jurisdiction may use the sizing listed
in Table 4. When using a single air supply, the duct shall
terminate within 305mm (12 in.) above and within
610mm (24 in.) horizontally from the burner level of the
appliance having the largest input.
For U.S.A. installations: Two openings (top and bot-
tom) shall be provided with each opening having a min-
imum 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.
(c) Equipment located in confined spaces; all air
from outdoors.
For Canadian installations: Refer to Table 4.
For U.S.A. installations: When supplying air directly
from the outdoors using horizontal ducting, each open-
ing 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.
(d) Equipment located in confined spaces; all air
from outdoors through ventilated attic.
For U.S.A. 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.
Combustion
Air Duct
Permanent
Ventilation
Air
12” Grade
12”
Outdoor
Air Ducts
Venting
Combustion
Inlet
Air Ducts
Outlet Air
(a)
(b)
(d)
(c)
Figure 4 Equipment Location and
Combustion/Ventilation Air Requirements
*U.S. installations require a dual duct system.
305mm
(12 in.)
305mm
(12 in.)
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