Combustion and Ventilation Air Supply
In order for the water heater to operate properly, it
must be supplied with an uninterrupted flow of clean
combustion and ventilation air. The area around the
water heater must always be kept clear and the com-
bustion air intake holes at the bottom of the water
heater must never be blocked. An inadequate supply
of air to the water heater will produce a bright yellow
burner flame causing sooting in the combustion cham-
ber, on the burner and in the flue tube. This can result
in damage to the water heater and serious bodily inju-
ry, if not corrected.
Combustion and ventilation air requirements are
determined by where the water heater is to be located.
Water heaters are installed in either open (uncon-
fined) 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)
ft
3
/1,000 BTU (4.8 m
3
/kW)
of the 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 particu-
larly 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) ft
3
/1,000 BTU (4.8 m
3
/kW)
of the total
input rating for all gas appliances installed in that
space. Water heaters installed in confined spaces
require additional air. This can be provided 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) in
2
/1,000 BTU (22.0 cm
2
/kW)
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 for all the appliances installed
in that confined space.
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 above
and within two (2) feet horizontally from the burner
level of the appliance having the largest input.
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.
4
INSTALLATION INSTRUCTIONS
Confined space
Confined space
Permanent
opening
--------------
1 in
2
/1,000 BTU/h
(min. : 100 in
2
)
Outlet air to attic
1 in
2
/4,000 BTU/h
Vent
to outdoors
Install above
insulation
Inlet air from the
crawl space
1 in
2
/4,000 BTU/h
Open foundation vent
Install above
insulation
Vent
to outdoors
Outlet air to attic
1 in
2
/4,000 BTU/h
Confined
space
Inlet air duct
Inlet air duct
1 in
2
/4,000 BTU/h
12'' max.
Inlet
Outlet
Outdoor air duct
1 in
2
/2,000 BTU/h
1 in
2
/2,000 BTU/h
Confined
space
Alternate
air inlet
Confined
space
Confined
space
18''
24''
Espace restreint
18''
24''
Entrée d'air
alternative
1 po
2
/2 000 BTU/h
1 po
2
/2 000 BTU/h
Conduite d'air extérieur
Sortie
Entrée
12'' max.
Conduite d'entrée d'air
Conduite
d'entrée d'air
1 po
2
/4 000 BTU/h
Évent de
fondation
1 po
2
/4 000 BTU/h
Entrée d'air du
sous-sol
Espace
restreint
Installez
au-dessus
de l'isolation
Installez
au-dessus
de l'isolation
Évent menant
à l'extérieur
Sortie d'air
au grenier
1 po
2
/4 000 BTU/h
Ouverture
permanente
--------------
1 po
2
/1 000 BTU/h
1 po
2
1 000 BTU/h
(min. : 100 po
2
)
Espace restreint
Espace
restreint
Évent menant
à l'extérieur
Espace
restreint
Sortie d'air
au grenier
1 po
2
/4 000 BTU/h
Espace
restreint
Figure 3
Figure 4
Figure 5
Figure 6
Figure 7
Figure 2
Permanent
opening
--------------
1 square inch/
1,000 BTU/h
Ouverture
permanente
--------------
Figure 2
Confined space
Confined space
Permanent
opening
--------------
1 in
2
/1,000 BTU/h
(min. : 100 in
2
)
Outlet air to attic
1 in
2
/4,000 BTU/h
Vent
to outdoors
Install above
insulation
Inlet air from the
crawl space
1 in
2
/4,000 BTU/h
Open foundation vent
Install above
insulation
Vent
to outdoors
Outlet air to attic
1 in
2
/4,000 BTU/h
Confined
space
Inlet air duct
Inlet air duct
1 in
2
/4,000 BTU/h
12'' max.
Inlet
Outlet
Outdoor air duct
1 in
2
/2,000 BTU/h
1 in
2
/2,000 BTU/h
Confined
space
Alternate
air inlet
Confined
space
Confined
space
18''
24''
Espace restreint
18''
24''
Entrée d'air
alternative
1 po
2
/2 000 BTU/h
1 po
2
/2 000 BTU/h
Conduite d'air extérieur
Sortie
Entrée
12'' max.
Conduite d'entrée d'air
Conduite
d'entrée d'air
1 po
2
/4 000 BTU/h
Évent de
fondation
1 po
2
/4 000 BTU/h
Entrée d'air du
sous-sol
Espace
restreint
Installez
au-dessus
de l'isolation
Installez
au-dessus
de l'isolation
Évent menant
à l'extérieur
Sortie d'air
au grenier
1 po
2
/4 000 BTU/h
Ouverture
permanente
--------------
1 po
2
/1 000 BTU/h
1 po
2
1 000 BTU/h
(min. : 100 po
2
)
Espace restreint
Espace
restreint
Évent menant
à l'extérieur
Espace
restreint
Sortie d'air
au grenier
1 po
2
/4 000 BTU/h
Espace
restreint
Figure 3
Figure 4
Figure 5
Figure 6
Figure 7
Figure 2
Permanent
opening
--------------
1 square inch/
1,000 BTU/h
Ouverture
permanente
--------------
Figure 3
2''
min.
2''
min.
4''
min.
18''
min.
2''
min.
Figure 1
