Lochinvar Shield SNR150-100 Installation & Service Manual page 14

1
Determine water heater location
Combustion air requirements are based on the latest edition
of the National Fuel Gas Code, ANSI Z223.1; in Canada refer
to the latest edition of CGA Standard CAN B149.1. Check all
local code requirements for combustion air.
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"
(30cm) of the ceiling and one must be within 12" (30cm) of
the floor of the equipment room. Each opening must have
net free area as specified in the chart above (Table 1B). Single
openings shall commence within 12" (30cm) of the ceiling.
Under no circumstances should the
CAUTION
equipment room ever be under 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.
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Installation & Service Manual
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The combustion air supply must be completely free of any
flammable vapors that may ignite or chemical fumes which
may be corrosive to the appliance. Common corrosive 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 stainless steel heat exchanger, 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 equipment room may deplete the combustion air
supply and/or cause a downdraft 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 equipment room, the installer must make sure that it
does not cause drafts which could lead to nuisance operational
problems with the appliance.