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Page 6 20248-2-0806
Water vapor is a by-product of gas combustion. An unvented room
heater produces approximately one (1) ounce (30ml) of water for
every 1,000 BTU's (.3KW's) of gas input per hour. .
Unvented room heaters are recommended as supplemental heat (a
room) rather than a primary heat source (an entire house). In most
supplemental heat applications, the water vapor does not create a
problem. In most applications, the water vapor enhances the low
humidity atmosphere experienced during cold weather.
The following steps will help insure that water vapor does not
become a problem.
1. Be sure the heater is sized properly for the application, including
ample combustion air and circulation air.
2. If high humidity is experienced, a dehumidifier may be used to
help lower the water vapor content of the air.
3. Do not use an unvented room heater as the primary heat
source.
This heater shall not be installed in a confined space or unusually
tight construction unless provisions 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. Weatherstripping 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. See “Ventilation Air From Outdoors,”
page 7.
Determining if You Have a Confined or Unconfined Space
Use this worksheet to determine if you have a confined or unconfined
space.
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 =
cu. ft. (volume of
space)
Example: Space size 16 ft. (length) x 10 ft. (width) x 8 ft. (ceiling
height) = 1,280 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. Divide the space volume by 50 cubic feet to determine the
maximum BTU/Hr the space can support.
(volume of space) ÷ 50 cu. ft. = (maximum
BTU/Hr the space can support)
Example: 1,280 cu. ft. (volume of space) ÷ 50 cu. ft. = 25.6 or
25,600 (maximum BTU/Hr the space can support)
PROVISIONS FOR ADEQUATE COMBUSTION & VENTILATION AIR
WATER VAPOR: A BY-PRODUCT OF UNVENTED ROOM HEATERS
SPECIFICATIONS
Model
VF24FP3-1 VF24FP2-1
Input Maximum 20,000 20,000/10,000
Minimum 14,000 7,000/7,000
Fireplace Dimensions
Height 26 3/8" 26 3/8"
Depth 10 7/8" 10 7/8"
Front Width 22 5/8" 22 5/8"
Rear Width 17 1/4" 17 1/4"
Gas Inlet 3/8" 3/8"
Accessories
VFS-BK Automatic Blower
EHL-24-1 Brick Liner
VPP1A-22 Aged Brick Liner
VPF24BR Brass Trim Kit
VPF24SS Stainless Steel Trim Kit
VPF24HP Hammered Pewter Trim Kit
Accessories for VF24FP3-1 Only
FRBC-1 Battery Operated Remote Control
FRBTC-1 Battery Operated Remote Control w/Thermostat
FREC-1 Electric Remote Control
FWS-1 Wall Switch
TMV Wall Thermostat, Millivolt - Reed Switch
TRW Wireless Remote Wall Thermostat