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INSTALLATION INSTRUCTIONS
Combustion and ventilation air requirements are
determined by where the water heater is to be located.
Water heaters are installed in either open (unconfined)
spaces or smaller (confined) spaces, such as closets or
small rooms.
Requirements for Unconfined Spaces
An unconfined space is an area with at least fifty (50)
cubic feet for each 1,000 BTUH (4.8 m
total input rating for all gas appliances installed in that
space. Water heaters installed in unconfined spaces
do not usually require outdoor air to function properly.
However, in buildings with tight construction (heavy
insulation, vapour barriers, weather stripping, etc.) and
particularly in modern buildings, additional fresh air
may need to be provided. For instructions on obtaining
additional air supply, see the requirements below for
confined spaces.
Requirements for Confined Spaces
A confined space is an area where the volume is less
than fifty (50) cubic feet for each 1,000 BTUH (4.8
3
m
/kW) of the total input rating for all gas appliances
installed in that space. Water heaters installed in con-
fined spaces require additional air. This can be pro-
vided in two ways:
In Canada (refer to CAN/CSA B149.1)
1) All Air From Inside the Building (see Figure 2):
The confined space shall be provided with
one opening of one (1) square inch per 1,000 BTUH
2
(22.0 cm
/kW) communicating directly with one or
more rooms of sufficient volume, so that the com-
bined volume of all spaces meets the criteria for an
unconfined space for all the appliances installed in
that confined space.
Figure 2
2) All Air From Outdoors: (see Figure 3):
An air supply shall be provided with one opening that
communicates directly with the outdoors by means
of a duct. This duct shall be sized according to CAN/
CSA B149.1 and terminate within one (1) foot (30.5
cm) above and within two (2) feet (61 cm) horizontally
3
/kW) of the
Confined Space
Permanent
Opening
--------------
1 square inches /
1000 BTUH
5
from the burner level of the appliance having the
largest input.
Figure 3
Confined Space
Inlet air duct
18''
In U.S.A. (refer to ANSI Z223.1/NFPA 54)
1) All Air From Inside the Building (see Figure 4):
The confined space shall be provided with two
permanent openings communicating directly with
one or more rooms of sufficient volume, so that
the combined volume of all spaces meets the
criteria for an unconfined space. The total input
rating of all gas appliances installed in the
combined space shall be considered in making this
determination.
Each opening shall have a minimum free area of one
(1) square inch per 1,000 BTUH (22.0 cm
total input rating of all gas appliances in the confined
space, but not less than one hundred (100) square
2
inches (645.16 cm
). One opening shall commence
within six (6) inches (15.2 cm) of the top and one within
six (6) inches (15.2 cm) of the bottom of the enclosure.
2) All Air From Outdoors:
The confined space shall be provided with two
permanent openings, one commencing within six
(6) inches (15.2 cm) of the top and one commencing
within six (6) inches (15.2 cm) from the bottom of the
enclosure. The openings shall communicate directly
or by ducts, with the outdoors or spaces (crawl or
attic) that freely communicate with the outdoors.
Figure 4
24''
2
/kW) of the
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