4
PROVISIONS FOR ADEQUATE COMBUSTION AND VENTILATION AIR
Today's homes are built more energy efficient than ever.
New materials, increased insulation and new construction
methods help reduce heat loss in homes. Home owners
weather strip and caulk around windows and doors to keep
the cold air out and the warm air in. During heating months,
home owners want their homes as airtight as possible.
While it is good to make your home energy efficient, you
need fresh air. All fuel-burning appliances need fresh air for
proper combustion.
SUPPLYING ADEQUATE VENTILATION
This appliance must be installed in an unconfined space.
The following information will help you classify your space
and provide adequate ventilation for complete combustion.
An Unconfined Space
has a minimum volume of 50 cubic
feet for each 1000 BTU/Hr input rating of all appliances in
the space. (4.8 m
3
per kw), (cubic feet equals length x width
x height of space).
A Confined Space
has a volume of less than 50 cubic feet
for each 1000 BTU/Hr input rating of all appliances in the
space, (4.8 m
3
per kw), (cubic feet equals length x width x
height of space).
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 25 ft. (length) x 25 ft. (width) x 8 ft.
(ceiling height) = 5,000 cu. ft. (volume of space)
?
If additional ventilation from adjoining room (s) is supplied
with grills or doorless openings, add the volume of these
rooms to compute the total volume of the applicable
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:
5,000 cu. ft. (volume of space) ÷ 50 cu. ft. =
100 or 100,000 (maximum BTU/Hr the space can
support)
3. Add the BTU/Hr of all gas burning appliances in the
space.
Gas range ________________ BTU/Hr
Vented gas heater __________ BTU/Hr
Gas fireplace logs ___________ BTU/Hr
Other gas appliances* + ______ BTU/Hr
Total = _____ BTU/Hr
Example:
Gas range 60,000 BTU/Hr
Vent-free logs +29,000 BTU/Hr
Total =89,000 BTU/Hr
?
*Do not include direct-vent gas appliances. Direct-vent
draws combustion air from the outdoors and vents to the
outdoors.
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)
Example:
100,000 BTU/Hr (maximum the space can
support) 89,000 BTU/Hr (actual amount of BTU/Hr used)
The space in the above example is an unconfined space
because the actual BTU/Hr used is less than the maximum
BTU/Hr the space can support. If the space had been
confined, your options would be as follows:
A. Rework worksheet, adding the space of an adjoining
room. If the extra space provides an unconfined space,
remove door to adjoining room or add ventilation grills
between rooms. See
Ventilation Air From Inside
Building.
B. Install a lower BTU/Hr heater, if lower BTU/Hr size
makes room unconfined.
CONVERTING CONFINED SPACE TO UNCONFINED
SPACE.
Additional volume to convert a confined to an unconfined
space could come from an adjoining space. When using an
adjoining space, you can provide two permanent openings:
one within 12" of the ceiling and one within 12" of the floor
on the wall connecting the two spaces (see options 1 and 2,
figure 2), or remove the door into the adjoining room.
VENTILATION AIR FROM OUTDOORS FOR
UNUSUALLY TIGHT CONSTRUCTION.
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 by one of the methods described in the
National Fuel Gas Code, ANSI Z223.1/NFPA 54, Section
5.3 or applicable codes.
WARNING: This heater shall not be installed in a
confined space or unusually tight construction unless
provisions are provided for adequate combustion
ventilation air.
The
National Fuel Gas Code, ANSI Z223.1
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
