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119526-01A 7
AIR FOR COMBUSTION
AND VENTILATION
Continued
Figure 4 - Ventilation Air from Outdoors
Figure 3 - Ventilation Air from Inside
Building
Outlet
Air
Ventilated
Attic
Outlet
A
ir
Inlet
Air
Inlet Air
Ventilated
Crawl Space
To
Crawl
Space
To Attic
Or
Remove
Door into
Adjoining
Room,
Option
3
Ventilation Grills
Into Adjoining Room,
Option 2
Ventilation
Grills
Into Adjoining
Room,
Option 1
12"
12"
VENTILATION AIR
Ventilation Air From Inside Building
This fresh air would come from an adjoining un-
conned space. When ventilating to an adjoining
unconned space, you must provide two perma-
nent openings: one within 12" of the ceiling and
one within 12" of the oor on the wall connecting
the two spaces (see options 1 and 2, Figure 3). You
can also remove door into adjoining room (see
option 3, Figure 3). Follow the National Fuel Gas
Code, ANSI Z223.1/NFPA 54, Section 5.3, Air for
Combustion and Ventilation for required size of
ventilation grills or ducts.
Ventilation Air From Outdoors
Provide extra fresh air by using ventilation grills or
ducts. You must provide two permanent openings:
one within 12" of the ceiling and one within 12"
of the oor. Connect these items directly to the
outdoors or spaces open to the outdoors. These
spaces include attics and crawl spaces. Follow the
National Fuel Gas Code, ANSI Z223.1/NFPA 54,
Section 5.3, Air for Combustion and Ventilation for
required size of ventilation grills or ducts.
IMPORTANT: Do not provide openings for inlet
or outlet air into attic if attic has a thermostat-
controlled power vent. Heated air entering the attic
will activate the power vent.
Example:
Gas water heater __________ Btu/Hr
Vent-free replace + ________ Btu/Hr
Total = ________ Btu/Hr
4. Compare the maximum Btu/Hr the space can
support with the actual amount of Btu/Hr used.
__________
Btu/Hr (maximum the space can support)
_________
Btu/Hr (actual amount of Btu/Hr used)
Example: 51,200 Btu/Hr (maximum the space
can support)
73,000 Btu/Hr (actual amount of
Btu/Hr used)
The space in the example is a conned space because
the actual Btu/Hr used is more than the maximum
Btu/Hr the space can support. You must provide ad-
ditional fresh air. Your options are as follows:
A. Rework worksheet, adding the space of an adjoin-
ing room. If the extra space provides an unconned
space, remove door to adjoining room or add
ventilation grills between rooms. See Ventilation
Air From Inside Building.
B. Vent room directly to the outdoors. See Ventila-
tion Air From Outdoors.
C. Install a lower Btu/Hr replace, if lower Btu/Hr
size makes room unconned.
If the actual Btu/Hr used is less than the maximum
Btu/Hr the space can support, the space is an un-
conned space. You will need no additional fresh
air ventilation.
WARNING: If the area in
which the heater may be oper-
ated is smaller than that dened
as an unconned space or if the
building is of unusually tight
construction, provide adequate
combustion and ventilation air
by one of the methods described
in the National Fuel Gas Code,
ANSI Z223.1/NFPA 54 Section 5.3
or applicable local codes.
40,000
33,000
73,000