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5
5
Gas water appliance _____________ Btu/Hr
Vent-free appliance + _____________
Btu/Hr
Total = _____________
Btu/Hr
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: 51,200 Btu/Hr (maximum the space can support)
73,000 Btu/Hr (actual amount of Btu/Hr used)
The space in the above example is a confined 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, 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, page 6.
B.Vent room directly to the outdoors. See Ventilation Air From Outdoors,
page 6.
C.Install a lower Btu/Hr appliance, if lower Btu/Hr size makes room unconfined.
If the actual Btu/Hr used is less than the maximum Btu/Hr the space can sup
port, the space is an unconfined space. You will need no additional fresh
air ventilation.
40,000
33,000
73,000
AIR FOR COMBUSTION AND
VENTILATION
Continued
DETERMINING FRESH-AIR FLOW FOR
APPLIANCE LOCATION
Determining if You Have a Confined or
Unconfined Space
Use this work sheet to determine if you have a confined or unconfined
space.
Space: Includes the room in which you will install appliance plus
any adjoining rooms with odorless 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 20 ft. (length) x 16 ft. (width) x 8 ft. (ceiling height)
2560 cu. ft. (volume of space)
AIR FOR COMBUSTION AND VENTILATION
Providing Adequate Ventilation (Cont.)
Determining Fresh-Air Flow for Appliance Location
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 (6 x 10
-11
kg per
pa-sec-m
2
) 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 ad
ditional fresh air. See Ventilation Air From Outdoors, page 5.
If your home does not meet all of the three criteria above, proceed to
Determining Fresh-Air Flow For Appliance Location, below.
Confined and Unconfined Space
The National Fuel Gas Code, ANSI Z223.1/NFPA 54 defines a confined space
as a space whose volume is 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 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.
* Adjoining rooms are communicating only if there are odorless passageways
or ventilation grills between them.
2.Multiply the space volume by 20 to determine the maximum Btu/Hr the
space can support.
____________(volume of space) x 20 = (Maximum Btu/Hr the space can
support)
Example: 2560 cu. ft. (volume of space) x 20 = 51,200 (maximum Btu/Hr
the space can support)
3.Add the Btu/Hr of all fuel burning appliances in the space.
Vent-free appliance _____________
Btu/Hr
Gas water appliance* _____________ Btu/Hr
Gas furnace _____________ Btu/Hr
Vented gas appliance _____________ Btu/Hr
Gas fireplace logs _____________
Btu/Hr
Other gas appliances* + _____________
Btu/Hr
Total = _____________ Btu/Hr
* Do not include direct-vent gas appliances. Direct-vent draws combustion
air from the outdoors and vents to the outdoors.
Example:
WARNING: If the area in which the appliance may be oper-
ated 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 Section 5.3
or applicable local codes.
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.
114745-01