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113110-01H 7
If your home meets all of these three cri-
Ventilation Air From Outdoors,
If your home does not meet all of the three
Determining
Fresh-Air Flow For Fireplace Location,
The National Fuel Gas Code, ANSI Z223.1/
NFPA 54 denes a conned space as a space
whose volume is less than 50 cubic feet per
1,000 Btu per hour (4.8 m
3
per kw) of the ag-
gregate input rating of all appliances installed
in that space and an unconned space as a
space whose volume is not less than 50 cubic
feet per 1,000 Btu per hour (4.8 m
3
per kw)
of the aggregate input rating of all appliances
installed in that space. Rooms communicating
directly with the space in which the appliances
are installed*, through openings not furnished
with doors, are considered a part of the un-
conned space.
* Adjoining rooms are communicating only if
there are doorless passageways or ventilation
grills between them.
DETERMINING FRESH-AIR FLOW
Use this work sheet to determine if you have
a conned or unconned space.
Includes the room in which you will
install replace 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 16 ft. (length) x 14 ft.
(width) x 8 ft. (ceiling height) = 1792 cu. ft.
(volume of space)
AIR FOR COMBUSTION AND VENTILATION
Continued
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 deter-
mine the maximum Btu/Hr the space can
support.
________ (volume of space) x 20 = (Maxi-
mum Btu/Hr the space can support)
Example: 1792 cu. ft. (volume of space) x 20
= 35,840 (maximum Btu/Hr the space can
support)
3. Add the Btu/Hr of all fuel burning appliances
in the space.
Vent-free replace ___________ Btu/Hr
Gas water heater* ___________ Btu/Hr
Gas furnace ___________ Btu/Hr
Vented gas heater ___________ Btu/Hr
Gas 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 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
us
ed)
Example: 35,840 Btu/Hr (maximum the
space can support)
40,000 Btu/Hr (actual amount of
Btu/Hr used)
The space in the example on the previous
page is a conned space because the actual
Btu/Hr used is more than the maximum Btu/Hr
the space can support. You must provide addi-
tional fresh air. Your options are as follows:
A. Rework worksheet, adding the space
of an adjoining 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, page 8
30,000
10,000
40,000