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1
Determine water heater location
FIG. 1-3
*Outside Air from
Model
2 Openings Directly from
Number
Outdoors
Top
Opening, in
38
SNR150-100
(246 cm
2
)
50
SNR200-100
(323 cm
2
)
72
SNA285-125
(465 cm
2
)
100
SNA400-125
(646 cm
2
)
125
SNA500-125
(807 cm
2
)
*Outside air openings shall directly communicate with the outdoors. When combustion air is drawn from the outside through a
duct, the net free area of each of the two openings must have twice (2 times) the free area required for Outside Air/2 Openings. The
above requirements are for the water heater only; additional gas fired appliances in the equipment room will require an increase in
the net free area to supply adequate combustion air for all appliances.
**Combined interior space must be 50 cubic feet per 1,000 Btu/hr input. Buildings MUST NOT be of *"Tight Construction". For
buildings of *"Tight Construction", provide air openings into the building from outside.
*No combustion air openings are needed when the water heater is installed in a space with a volume NO LESS than 50 cubic feet
per 1,000 Btu/hr of all installed gas fired appliances. Buildings MUST NOT be of *"Tight Construction".
*"Tight Construction" is defined as a building with less than 0.40 ACH (air changes per hour).
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
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.
MINIMUM RECOMMENDED COMBUSTION
AIR SUPPLY TO EQUIPMENT ROOM
*Outside Air from
2 Ducts Delivered from
Bottom
Top
2
Opening, in
2
Opening, in
38
75
(246 cm
2
)
(484 cm
50
100
(323 cm
2
)
(646 cm
72
143
(465 cm
2
)
(923 cm
100
200
(646 cm
2
)
(1,291 cm
125
250
(807 cm
2
)
(1,613 cm
no
circumstances
should
(continued)
TABLE - 1B
FIG. 1-4
2 Ducts Delivered from Interior
Outdoors
Bottom
Top
2
Opening, in
2
Opening, in
75
2
)
(484 cm
2
)
(968 cm
100
2
)
(646 cm
2
)
(1,291 cm
143
2
)
(923 cm
2
)
(1,839 cm
200
2
)
(1,291 cm
2
)
(2,581 cm
250
2
)
(1,613 cm
2
)
(3,226 cm
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
the
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.
Installation & Service Manual
TM
FIG. 1-5
**Inside Air from
Space
Bottom
2
Opening, in
2
150
150
2
)
(968 cm
2
)
200
200
2
)
(1,291 cm
2
)
285
285
2
)
(1,839 cm
2
)
400
400
2
)
(2,581 cm
2
)
500
500
2
)
(3,226 cm
2
)
FIG. 1-6
*Outside Air from
1 Opening Directly
from Outdoors, in
2
50
(323 cm
2
)
67
(433 cm
2
)
95
(613 cm
2
)
134
(865 cm
2
)
167
(1,078 cm
2
)
13
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