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112471-01B
7
AIR FOR COMbUSTION
AND VENTILATION
Continued
DETERMINING FRESH-AIR FLOW
FOR HEATER LOCATION
Determining if You Have a Confined or
Unconfined Space
Use this work sheet to determine if you have a
confined or unconfined space.
Space:
Includes the room in which you will install
heater plus any adjoining rooms with doorless pas
-
sageways 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 20 ft. (length) x 16 ft.
(width) x 8 ft. (ceiling height) = 2560 cu. ft.
(volume of space)
If additional ventilation to adjoining room is
supplied 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:
2560 cu. ft. (volume of space) x 20 =
51,200 (maximum Btu/Hr the space can support)
3. Add the Btu/Hr of all fuel burning appliances
in the space.
Vent-free heater
___________
Btu/Hr
Gas water heater*
___________
Btu/Hr
Gas furnace
___________
Btu/Hr
Vented gas heater
___________
Btu/Hr
Gas fireplace logs
___________
Btu/Hr
Other gas appl
__________
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 heater
+
___________
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 above example is a confined
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
unconfined 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
Ven-
tilation Air From Outdoors
, page 8.
C. Install a lower Btu/Hr heater, if lower Btu/Hr
size makes room unconfined.
If the actual Btu/Hr used is less than the maxi
-
mum Btu/Hr the space can support, the space is
an unconfined 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 defined
as an unconfined 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.
VENTILATION AIR
Ventilation Air From Inside Building
This fresh air would come from an adjoining un
-
confined space. When ventilating to an adjoining
unconfined space, you must provide two perma
-
nent openings: one within 12" of the ceiling and
one within 12" of the floor on the wall connecting
the two spaces (see options 1 and 2, Figure 2,
page 8). You can also remove door into adjoining
room (see option 3, Figure 2, page 8). 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.
40,000
33,000
73,000
