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OWNER'S MANUAL
AIR FOR
COMBUSTION AND
VENTILATION
Continued
DETERMINING FRESH-AIR FLOW FOR FIREPLACE LOCATION
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 firebox 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 22 ft. (length) x 18 ft. (width) x 8 ft. (ceiling height) = 3168 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: 3168 cu. ft. (volume of space) .'-50 cu. ft. = 63.3 or 63,300 (maximum Btu/Hr the space can support)
3. Add the Btu/Hr of all fuel burning appliances in the space.
Vent-free firebox Btu/Hr
Gas water heater* Btu/Hr Example:
Gas furnace Btu/Hr Gas water heater 40,000 Btu/Hr
Vented gas heater Btu/Hr Vent-free firebox with log heater + 39,000 Btu/Hr
Gas firebox logs Btu/Hr Total 79,000 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.
4. Compare the tnaximum Btu/Hr the space can support with the actual amount of Btu/Hr used.
Btu/l-lr (maximum the space can support)
Btu/Hr (actual amount of Btu/Hr used)
Example: 63,300 Btu/Hr (maximum the space can support)
79,000 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.
Yon 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 adjoin-
ing 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 fireplace, if lower Btu/I-Ir size makes room unconfined.
"If the actual Btu/Hr used is less than the maximum Btu/Hr the space can support, the space is an unconfined space. You will need no
additional fresh air ventilation.
I
_lb WARNING: If the area In which the firebox end gas log heater may be operated is smeller than that defined as I
an unconfined space or If the building Is of unusually tight construction, provide adequate combustion and
I
ventilation air by one of the methods described in the National Fuel Gas Code, ANS Z223.1, 1992, Section 5.3 or
eppllceble local codes.
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