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G. Adequate Combustion Ventilation Air
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, (ANSI Z223.1/NFPA54),
defines a confined space as a space whose volume is less
than 50 cubic feet per 1,000 BTU per hour (4.8m
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
per kw) of the aggregate input rating of all
3
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 a confined space.
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
1 perm (6 x 10
kg per pa/sec-m
11
gasketed or sealed, and
b. Weather stripping has been added to 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 other openings.
The following formula can be used to determine the maxi-
mum heater rating per the definition of unconfined space:
BTU/Hr = (L
+ L
1
Consider two connecting rooms with an open area
between, with the following dimensions:
L
= 15
/
Ft., L
= 12 Ft., W = 12 Ft., H = 8 Ft.
1
1
2
2
BTU/Hr = (15
If there were a door between the two rooms the calculation
would be based only on the room with the heater.
BTU/Hr = (15
8
3
) or less with openings
2
) Ft x (W) Ft x (H) Ft
2
50
/
+ 12) x (12) x (8)
1
2
50
/
) x (12) x (8)
1
2
50
Monessen • Mojo Installation/Owner's Manual • 4623-900 Rev. F • 01/23
per kw)
Figure 2.3
If the area in which the heater may be
operated does not meet the required volume
for indoor combustion air, combustion and
ventilation air shall be provided by one
of the methods described in the National
Fuel Gas Code, ANSI Z223.1/NFPA 54, the
International Fuel Gas Code or applicable
local codes.
Counter
W
WARNING
Fireplace
H
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