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.
When installed in a closet, DO NOT block
or obstruct any of the combustion air inlet
openings located around the perimeter
of the water heater. A minimum of 1” is
required between these combustion air inlet
openings and any obstruction.
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 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” above the floor
and the other is to be located within 12”
from the ceiling.
The minimum net free area of each opening
must not be less than one square inch
per 1000 Btuh of the total input rating
of all the appliances in the enclosure
(but not less than 100 square inches), 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 per 4000
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 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
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”mesh to prevent
clogging by lint or other debris.
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
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
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
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