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*Adjoining rooms are communication only if there
are door less passageways or ventilation grills
between them.
DETERMINING THE TYPE OF HEATER
LOCATION SPACE:
Use this method to determine if you have a confi ned or
unconfi ned space.
Note: the space includes the room in which you
install heater plus any adjoining rooms with doorless
passageways or ventilation grills between the rooms.
1. Find the volume of the space by multiplying room
length x width x height.
Example: Space size 18ft (length) x 18ft. (width) x 8ft.
(height) = 2592
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. Divide the space volume by 50 cubic feet to deter-
mine the maximum Btu/hr the space can support.
Example: 2592 cu.ft. (volume of space) / 50 cu.ft. =
51.8 or 51,800 (maximum Btu/hr the space
can support)
WARNING: If the area in which the heater may be
operated is smaller than defi ned as an unconfi ned
space or if the building is of unusually tight
construction, provide adequate combustion and
ventilation air by the methods described in the
National Fuel Gas Code, NFPA 54/ ANSI Z223.1,
Section 5.3 or applicable local codes.
3. Add the Btu/hr of all the fuel-burning appliances
in the space such as, Vent–free heater, Gas water
heater, Gas furnace, Vented gas heater, Gas fi re-
place logs, and Other gas appliances*
*Do not include direct-vent gas appliances. Direct-
vent draws combustion air from the outdoors and
vents to the outdoors.
Example:
Gas water heater
Vent Free Heater +
Total
4. Compare the maximum Btu/hr the space can support
with the actual amount of Btu/hr used.
Example:
51,800 Btu/hr (maximum Btu/hr the
space can support)
60,000 Btu/hr (Actual amount of Btu/hr
used)
The space in the above 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, and 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 the rooms. See Ventilation
40,000 Btu/hr
20,000 Btu/hr
=60,000 Btu/hr
Unvented LP-Gas Vent Free Room Heaters
Air From Inside Building (Figure 2).
B. Vent room directly to the outdoors. See Ventilation
Air From Outdoors (Figure 3).
C. Install a lower Btu/hr heater if lower Btu/hr size
makes room unconfi ned.
If actual Btu/hr used is less than the maximum Btu/
hr the space can support, the space is an uncon-
fi ned space. You will need no additional fresh air
ventilation.
VENTILATION AIR
Ventilation from Inside Building
This fresh air would come from an adjoining unconfi ned
space. When ventilation 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 & 2 of fi g. 2). You can also remove door into
adjoining room (see option3, fi g 2). Follow the National
Fuel Gas Code NFPA 54/ ANSI Z223.1, Section 5.3,
Air for Combustion and Ventilation for required size of
ventilation grills or ducts.
Or remove
Ventilation
door into
Gills into
Adjoining
Adjoining
Room -
Room -
Option 3
Option 1
OUTLET AIR
OUTLET
AIR
INLET
AIR
Installation Instructions and Owner's Manual
5
12"
Ventilation Gills into
Adjoining Room - Option 2
12"
Figure 2.
VENTILATION AIR
VENTILATED
ATTIC
TO ATTIC
TO CRAWL
SPACE
VENTILATION CRAWL SPACE
Figure 3.
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