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8
Installing the water heater.
Combustion and Ventilation Air
Proper operation of the water heater
requires air for combustion and
ventilation. Provisions for combustion
and ventilation air must comply with
referenced codes and standards.
NOTICE: If the water heater is installed in
an unconfined space within a building of
conventional frame, masonry or metal
construction, infiltration air is normally
adequate for proper combustion and
ventilation. If the water heater is installed in
a confined space, provisions for combustion
and ventilation air must be made.
A confined space is one having a volume
of less than 50 cubic feet (1.4 cubic
metres) per 1000 Btuh of the aggregate
input of all appliances within that space.
The air must be supplied through two
permanent openings of equal area. One is
to be located within 12” (30.5cm) above
the floor and the other is to be located
within 12” (30.5cm) from the ceiling.
The minimum net free area of each opening
must not be less than one square inch
(6.5sq. cm) per 1000 Btuh of the total
input rating of all the appliances in the
enclosure (but not less than 100 square
inches (650sq cm)), if each opening
communicates with other unconfined areas
inside the building.
Buildings of unusually tight construction
shall have the combustion and ventilation
air supplied from outdoors, or a freely
ventilated attic or crawl space.
If air is supplied from outdoors, directly or
through vertical ducts, there must be two
openings located as specified above and
each must have a minimum net free area
of not less than one square inch
(6.5sq. cm) per 1000 Btuh of the total
input rating of all the appliances in the
enclosure.
If horizontal ducts are used to
communicate with the outdoors, each
opening must have a minimum net free
area of not less than one square inch
(6.5sq. cm) per 2000 Btuh of the total
input rating of all the appliances in the
enclosure. If ducts are used, the minimum
dimensions of rectangular air ducts shall
not be less than 3” (7.62cm).
NOTICE: If the duct openings which supply
combustion and ventilation air are to be
covered with a protective screen or grill, the
net free area (openings in the material) of
the covering material must be used in
determining the size of the openings.
Protective screening for the openings MUST
NOT be smaller than 1/4” (0.64cm) mesh to
prevent clogging by lint or other debris.
Corrosive Atmospheres
The air in beauty shops, dry cleaning
establishments, photo processing labs,
and storage areas for liquid and powdered
bleaches or swimming pool chemicals
often contain such halogenated
hydrocarbons.
An air supply containing halogenated
hydrocarbons may be safe to breathe,
but when it passes through a gas flame
corrosive elements are released that
will shorten the life of any gas burning
appliance.
Propellants from common spray cans or
gas leaks from A/C and refrigeration
equipment are highly corrosive after
passing through a flame.
The water heater warranty is voided when
failure of the heater is due to operation in
a corrosive atmosphere.
NOTICE: The water heater
should not be installed near
an air supply containing
halogenated hydrocarbons.
Inspect Shipment
Inspect the water heater for possible damage. Check the markings on the rating plate of
the water heater to be certain the type of gas supplied corresponds to the water heater
requirements.
CAUTION: For
COMMERCIAL models
ONLY - Large exhaust
fans can lower the air
pressure inside a building
or room and interfere
with proper venting and
operation. Commercial
kitchens or other
locations that must
maintain a high flow of
exhaust air should have
the water heater installed
in a separate room with
combustion and
ventilation air supplied
directly from outside as
described to the right.