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126700-01B
9
AIR FOR COMBUSTION AND VENTILATION
Continued
Figure 4 - Ventilation Air from Inside
Building
Or
Remove
Door into
Adjoining
Room,
Option
3
Ventilation Grills
Into Adjoining Room,
Option 2
Ventilation
Grills Into
Adjoining
Room,
Option 1
12"
12"
Use this work sheet to determine if you have a
confi ned or unconfi ned space.
Space:
Includes the room in which you will install
heater plus any adjoining rooms with doorless
passageways or ventilation grills between the
rooms.
1. Determine the volume of the space (length x
width x height).
Length x Width x Height =__________cu. ft.
(volume of space)
Example:
Space size 22 ft. (length) x 18 ft.
(width) x 8 ft. (ceiling height) = 3,168 cu. ft.
(volume of space)
If additional ventilation to adjoining room is sup-
plied with grills or openings, add the volume of
these rooms to the total volume of the space.
2. Multiply the space volume by 20 to determine the
maximum Btu/Hr the space can support.
________ (volume of space) x 20 = (Maximum
Btu/Hr the space can support)
Example:
3,168 cu. ft. (volume of space) x 20 =
63,360 (maximum Btu/Hr space can support)
3. Add the Btu/Hr of all fuel burning appliances in
the space.
Vent-free
fi replace
_________ Btu/Hr
Gas water heater*
_________ Btu/Hr
Gas
furnace
_________ Btu/Hr
Vented gas heater
_________ Btu/Hr
Gas
fi replace logs
_________ Btu/Hr
Other gas appliances* + _________ Btu/Hr
Total
=
_________ Btu/Hr
* Do not include direct-vent gas appliances.
Direct-vent draws combustion air from the
outdoors and vents to the outdoors.
Example:
Gas water heater
_________ Btu/Hr
Vent-free
fi 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:
63,360 Btu/Hr (maximum the space
can support)
79,000 Btu/Hr (actual amount of Btu/
Hr used)
The space in the example is a confi ned space
because the actual Btu/Hr used is more than the
maximum Btu/Hr the space can support. You must
provide additional fresh air. Your options are as
follows:
A. Rework worksheet, adding the space of an
adjoining room. If the extra space provides an
unconfi ned 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,
Page 10
.
C. Install a lower Btu/Hr fi replace, if lower Btu/Hr
size makes room unconfi ned.
If the actual Btu/Hr used is less than the maxi-
mum Btu/Hr the space can support, the space is
an unconfi ned space. You will need no additional
fresh air ventilation.
40,000
39,000
79,000
WARNING: If the area in which
the heater may be operated does
not meet the required volume for
indoor combustion air, combus-
tion and ventilation air shall be
provided by one of the methods
described in the National Fuel Gas
Code, ANSI Z223.1/NFPA 54, the
International Fuel Gas Code, or
applicable local codes.
VENTILATION AIR
Ventilation Air From Inside Building
This fresh air would come from an adjoining
unconfined space. When ventilating to an
adjoining unconfi ned space, you must provide
two permanent openings: one within 12" of the
ceiling and one within 12" of the fl oor on the wall
connecting the two spaces
(see options 1 and
2, Figure 4)
. You can also remove door into ad-
joining room
(see option 3, Figure 4)
. Follow the
National Fuel Gas Code, ANSI Z223.1/NFPA 54,
Air for Combustion and Ventilation
for required
size of ventilation grills or ducts.
