Filter
Top Products
www.fmiproducts.com
121353-01H 7
DETERMINING FRESH-AIR FLOW
FOR HEATER LOCATION
Use this work sheet to determine if you have
a conned or unconned 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 = __________ c u .
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 = (Maxi-
mum 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 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 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)
40,000
33,000
73,000
Example: 51,200 Btu/Hr (maximum the
space can support)
73,000 Btu/Hr (actual amount of Btu/Hr
used)
The space in this 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 additional 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.
B. Vent room directly to the outdoors. See
Ventilation Air From Outdoors, page 8.
C. Install a lower Btu/Hr heater, if lower Btu/Hr
size makes room unconned.
If the actual Btu/Hr used is less than the maxi-
mum Btu/Hr the space can support, the space is
an unconned space. You will need no additional
fresh air ventilation.
WARNING: If the area in which
-
National Fuel
Gas Code, ANSI Z223.1/NFPA 54,
the International Fuel Gas Code,
This fresh air would come from an adjoining
unconned space. When ventilating to an
adjoining unconned space, you must provide
two permanent 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 2, page 8). You can
also remove door into adjoining room (see
option 3, Figure 2). Follow the National Fuel
Gas Code, ANSI Z223.1/NFPA 54, Air for
Combustion and Ventilation for required size
of ventilation grills or ducts.
AIR FOR COMbUSTION AND VENTILATION
Continued