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UNVENTED PROPANE/LP GAS LOG HEATER
VANGUARD FLAME-MAX™
DETERMINING AIR FLOW
FOR HEATER 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 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 20 ft. (length) x
16 ft. (width) x 8 ft. (ceiling height) =
2560 cu. ft. (volume of space)
If additional ventilation to adjoining
room is supplied with grills or open-
ings, 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:
2560 cu. ft. (volume of
space) ÷ 50 cu. ft. = 51.2 or 51,200
(maximum Btu/Hr the space can sup-
port)
3. Add the Btu/Hr of all fuel burning ap-
pliances in the space.
Vent-free heater __________ Btu/Hr
Gas water heater* ________ Btu/Hr
Gas furnace _____________ Btu/Hr
Vented gas heater _________ Btu/Hr
Gas fireplace logs ________ Btu/Hr
Other gas appliances* + ___ Btu/Hr
Total = ___ Btu/Hr
AIR FOR
COMBUSTION AND
VENTILATION
Continued
Unusually Tight Construction
The air that leaks around doors and win-
dows 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 de-
fined 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 (6x10
-11
kg
per pa-sec-m
2
) or less with open-
ings 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, be-
tween sole plates and floors, be-
tween wall-ceiling joints, be-
tween wall panels, at penetra-
tions 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
De-
termining Air Flow For Heater Loca-
tion
.
Confined and Unconfined Space
The National Fuel Gas Code (ANSIZ223.1,
1992 Section 5.3) 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 in-
stalled*, through openings not furnished
with doors, are considered a part of the
unconfined space.
* Adjoining rooms are communicating only
if there are doorless passageways or ventila-
tion grills between them.
Example:
Gas water heater 40,000 Btu/Hr
Vent-free heater + 31,500 Btu/Hr
Total = 71,500 Btu/Hr
* Do not include direct-vent gas appli-
ances. 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:
51,200 Btu/Hr (maximum
the space can support)
71,500 Btu/Hr (actual amount of Btu/
Hr used)
The space in the above example is a con-
fined 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 ventila-
tion grills between rooms. See Ventila-
tion Air From Inside Building, page 5.
B. Vent room directly to the outdoors. See
Ventilation Air From Outdoors, page 5.
C. Install a lower Btu/Hr heater, if lower
Btu/Hr 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.