American Water Heater DCG - Manual (Page 7)

7
Air Requirements For buildings that are not well sealed (do not have tight
fitting doors and windows) natural air infiltration may
provide sufficient air required for combustion and venti-
lation. For buildings using tight construction (newer and
renovated structures), the air supply shall be introduced
from the outdoors, regardless of whether the space is
confined or unconfined.
Combustion Air “Supply” Ducts
Air supply ducts shall be of galvanized steel or equiva-
lent corrosion resistant material. A single air duct may
not be substituted when required for upper and lower
air openings. Horizontal upper combustion air ducts
shall not slope downward toward the air inlet.
Louvers and Grills
Openings for air supply ducts must provide free unob-
structed 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 location for top and bottom openings are as fol-
lows;
For U.S. installations:The top opening shall com-
mence within 12” (300 m) of the top of space and the
bottom opening shall commence within 12” (300mm) of
the bottom of the enclosure.
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 18 inches (450 mm), nor less than 6 inches
(150 mm), above floor level.
General
Where an exhaust fan or any other air consuming
appliance (Eg. Clothes dryer, furnace, etc.) is installed
in the same space as the water heater, sufficient air
openings must be available to provide fresh air when all
appliances are operating simultaneously.
The area in which the heater is located is classified as
either “an unconfined space” or “a confined space.”
An unconfined space is defined as a space having a
volume not less than 50 cubic feet per 1000 BTU/hour
(4.8 cubic meters per kilowatt) of combined input rating
of all appliances using the space. Adjacent open rooms
may be included as part of the unconfined space.
There shall be no closeable doors between these
rooms. An example of this is an open basement.
A confined space is one smaller than described above.
Air shall be supplied through permanent openings as
described in Figure 2. At no time shall an air opening
have a dimension of less than 3” (75 mm) and at no
time shall any top opening be lower than the top of the
water heater.
An adequate air supply shall be provided
for combustion and ventilation of this
water heater.
An insufficient supply can result in poor
combustion and possible sooting of the
burner, combustion chamber or flue
passageway. This may present a potential
fire hazard or could create a serious
health hazard by producing carbon
monoxide.
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