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ventilation air by one of the methods described in the National Fuel
Gas Code, ANSI Z223.1, Section 5.3. or applicable local codes.
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, Section 5.3.
Adhere to all codes, or in their absence, the latest edition of THE
NATIONAL FUEL GAS CODE ANSI Z223.1 or NFPA54 which can be
obtained from:
American National Standards Institute National Fire Protection Association, Inc.
11 West 42nd St. Batterymarch Park
New York, NY 10018 Quincy, MA 02269
Minimum Dimensions For Solid Fuel Burning Fireplaces
UL127 Factory Built Fireplaces (Figure 2)
Model A B C D
VFDR18 17" 12" 28" 17"
VFDR24 23" 12" 30" 18"
VFDR30 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 provi-
sions are provided for adequate combustion and ventilation air.
The National Fuel Gas Code defines a confined space as a space
whose volume is less than 50 cubic feet per 1,000 Btu per hour
(4.8m
3
per kw) of the aggregate input rating of all appliances
installed in that space and an unconfined 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 unconfined 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 continuous 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
PROVISIONS FOR ADEQUATE COMBUSTION & VENTILATION AIR
CLEARANCES