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1
Determine water heater location
All dimensions based on net free area in square inches.
Metal louvers or screens reduce the free area of a combustion
air opening a minimum of approximately 25%. Check with
louver manufacturers for exact net free area of louvers.
Where two openings are provided, one must be within
12"(30 cm) of the ceiling and one must be within 12" (30
cm) of the floor of the mechanical room. Each opening
must have net free area as specified in Table A. Single
openings shall commence within 12" (30 cm) of the ceiling.
Under no circumstances should the
CAUTION
equipment room ever be under a negative
pressure. Particular care should be taken
where exhaust fans, attic fans, clothes
dryers, compressors, air handling units,
etc. may take away air from the unit.
The combustion air supply must be completely free of any
chemical fumes which may be corrosive to the appliance.
Common chemical fumes which must be avoided are
fluorocarbons and other halogenated compounds, most
commonly present as refrigerants or solvents, such as
Freon, trichlorethylene, perchlorethylene, chlorine, etc.
These chemicals, when burned form acids which quickly
attack the heat exchanger finned tubes, tube headers, flue
collectors, and the vent system. The result is improper
combustion and a non-warrantable, premature appliance
failure.
EXHAUST FANS: Any fan or equipment which exhausts
air from the mechanical room may deplete the combustion
air supply and/or cause a down draft in the venting system.
Spillage of flue products from the venting system into an
occupied living space can cause a very hazardous condition
that must be immediately corrected. If a fan is used to
supply combustion air to the room, the installer must
make sure that it does not cause drafts which could lead to
nuisance operational problems with the appliance.
E+Vent and Direct Vent venting systems have specific
requirements for combustion air ducts from the outside
which are directly connected to the appliance. See the
requirements for this combustion air duct in the venting
section for each specialized vent system.
Installation & Service Manual
(continued)
7
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