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Example of Large Room with 1/2 Wall divider.
Figure 1
The following formula can be used to determine the maximum heater rating
per the definition of unconfined space:
Btu/Hr =
(L
1
+ L
2
)FT x (W)FT x (H)FT
x 1000
50
If the area in which the heater may be operated is smaller than that defined
as an unconfined space, provide adequate combustion and ventilation air
by one of the methods described in the
National Fuel Gas Code, ANSI
Z223.1/NFPA54.
Adhere to all codes, or in their absence, the latest edition of
THE NATIONAL
FUEL GAS CODE ANSI Z223.1/NFPA54
which can be obtained from:
American National Standards Institute
11 West 42nd St.
New York, NY 10018
OR
National Fire Protection Association, Inc.
Batterymarch Park
Quincy, MA 02269
Minimum Dimensions For Solid Fuel Burning Fireplaces UL127
Factory Built Fireplaces (Figure 2)
Model
A
B
C
D
VFDR18LB10
17"
12"
28"
17"
VFD(R,T,M)18
17"
12"
28"
17"
VFD(R,T,M)24
23"
12"
30"
18"
VFD(R,T,M)30
26"
12"
34"
20"
The dimensions shown and defined in the fireplace manufacturer’s
instructions are minimum clearances to maintain in installing this
heater. Left and right clearances are determined when facing the
front of the heater.
Glass Doors
Make sure that glass doors are open during all operations of
the logset. The opening of the glass door frame should be the
dimension used for the minimum front opening of the firebox.
Follow these instructions to ensure safe installation.
Failure to follow instructions exactly can create a fire hazard.
Figure 2
This heater shall not be installed in a confined space unless provisions are
provided for adequate combustion and ventilation air.
A confined space is an area with volume less than 50 cubic feet per 1,000
Btuh of the combined input rates of all appliances drawing combustion
air from that space. Small areas such as equipment rooms are confined
spaces. Furnaces installed in a confined space which supply heated air to
areas outside the space must draw return air from outside the space through
tightly sealed return air ducts. A confined space must have 2 openings into
the space for combustion air. One opening must be within 12 inches of the
ceiling and the other must be within 12 inches of the floor. The required
sizing of these openings is determined by whether inside or outside air is
used to support combustion, the method by which the air is brought to the
space (vertical or horizontal duct) and by the total input rate of all appli-
ances in the space.
Unusually Tight Construction
The air that leaks around doors and windows may provide enough fresh
air for combustion and ventilation. However, in buildings of unusually tight
construction, you must provide additional fresh air.
Unusually tight construction is defined as construction where:
a. Walls and ceilings exposed to the outside atmosphere have a con-
tinuous water vapor retarder with a rating of one perm or less with
openings gasketed or sealed, and
b. Weather-stripping has been added on openable windows and doors,
and
c. Caulking or sealants are applied to areas such as joints around
window and door frames, between sole plates and floors, between
wall-ceiling joints, between wall panels, at penetrations for plumbing,
electrical, and gas lines, and at other openings.
If your home meets all of the three criteria above, you must provide
additional fresh air.
wARNING
If the area in which the heater may be operated 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, Air for
Combustion and Ventilation, or applicable local codes.
PROVISIONS FOR ADEQUATE COMBUSTION & VENTILATION AIR
CLEARANCES
