as any other appliances that may consume air in the space.
Always follow local codes if they are more stringent.
This Installation Manual specifies the minimum vertical vent
pipe and the amount of combustion air required for this unit.
When all requirements are followed, the unit will operate
properly and safely. However, there may still be a risk of
freezing due to negative draft if the other combustion
appliances in the building are not supplied with sufficient
combustion air. A wood stove or furnace can pull its combustion
air from the heater's vent pipe, allowing the cold incoming air to
freeze the cold water in the heat exchanger. Supplying more
combustion air for all combustion appliances is the solution. A
HVAC specialist should be consulted to design solutions for
providing more combustion air.
Observe the following guidelines:Installations in structures that
have been tightly constructed (air infiltration rate of 0.40 ACH
or less) must be provided with combustion air per the National
Fuel Gas Code. Consult a HVAC specialist if your air infiltration
rate is questionable.The space must have two permanent
openings, one commencing within 12 inches of the top and one
commencing within 12 inches of the bottom of the enclosure.
Appliances located in unconfined spaces:
– a) An unconfined space is one whose volume is greater
than 50 cubic feet (1.42 cubic meter) per 1000 BTU/
hr (292.81 Watts) of the combined rating of all
appliances installed in the space. That would be 9950
cubic feet (281.8 cubic meters) for the water heater
– b) In unconfined spaces in buildings of conventional
frame, masonry, or metal construction, infiltration air is
normally adequate to provide air for combustion.
Appliances located in confined spaces:
The confined space must be provided with two permanent
openings, one commencing within 12 inches (304.8mm)
of the top and one commencing within 12 inches
(304.8mm) of the bottom of the enclosure. Each opening
must have a minimum free area of one square inch per:
– 1000 BTU/hr (292.81 Watts) if all air is taken from
inside the building
– 2000 BTU/hr (585.62 Watts) if all air is taken from the
outside by horizontal ducts
– 4000 BTU/hr (1171.24 Watts)if all air is taken from
the outside by direct openings or vertical ducts
Or the confined space must be provided with one permanent
opening or duct that is within 12 inches (304.8mm) of the
ceiling of the enclosure. This opening must have a minimum
free area of one square inch per:
– 3000 BTU/hr (878.43 Watts) if all air is taken from the
outside by a direct opening or vertical duct.
Louvers, grills and screens have a blocking effect, when used,
increase the sizes of your openings by 300% for wood louvers
(as wood type will reduce the free air by 75%) and 43% for
metal louvers (as metal will reduce the free air by 30%). Refer
to the National Fuel Gas Code for complete information. In
buildings of tight construction all air should be taken from
Proper location for installing your heater
Carefully select the location of the water heater. For your safety
and for proper heater operation, you must provide combustion
air to the heater and a proper exhaust vent system.
Follow the guidelines below:
▶ 1. Locate the heater where venting, gas and plumbing
connections are feasible and convenient.
▶ 2. The hot water lines should be kept short and insulated to
save energy. Centrally locating the water heater is
recommended to keep hot water distribution times even
throughout the structure.
Risk of appliance freezing!
▶ The water in this water heater is cold and always remains
cold except for the times the burner is on. In the event of
power outage in conjunction with freezing temperatures, it
is recommended that the heater be drained.
See chapter 7.2, page 51 "Winterizing" for draining
▶ Flammable materials, gasoline, pressurized containers, or
any other items or articles that are potential fire hazards
must NOT be placed on or adjacent to the heater. The
appliance area must be kept free of all combustible
materials, gasoline and other flammable vapors and
Heater placement and clearances
The water heater design is approved for installation on a
combustible wall (see chapter 4.7 Mounting installation)
provided the floor covering below the heater is
For installations in an alcove or closet, maintain the minimum
clearances to combustible and non-combustible materials. See
fig. 6, page 14.
940 ES – 6 720 644 930 (2019/09)