Desa Unvented (Vent-Free) Gas Compact Classic Hearth Fireplace VMH26NRB Owner's Operation And Installation Manual page 7

AIR FOR COMBUSTION AND VENTILATION
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 these three cri-
teria, you must provide additional fresh
air. See Ventilation Air From Outdoors,
page 8.
If your home does not meet all of the three
criteria above, proceed to Determining
Fresh-Air Flow For Fireplace 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
gregate 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
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 un-
confined space.
* Adjoining rooms are communicating only if
there are doorless passageways or ventilation
grills between them.
DETERMINING FRESH-AIR FLOW
FOR FIREPLACE LOCATION
Determining if You Have a Confined or
Unconfined Space
Use this work sheet to determine if you have
a confined or unconfined space.
Includes the room in which you will
Space:
install fireplace 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 16 ft. (length) x 14 ft.
(width) x 8 ft. (ceiling height) = 1792 cu. ft.
(volume of space)
113110-01H
Continued
per kw) of the ag-
3
per kw)
3
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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. Multiply the space volume by 20 to deter-
mine the maximum Btu/Hr the space can
support.
________ (volume of space) x 20 = (Maxi-
mum Btu/Hr the space can support)
Example: 1792 cu. ft. (volume of space) x 20
= 35,840 (maximum Btu/Hr the space can
support)
3. Add the Btu/Hr of all fuel burning appliances
in the space.
Vent-free fireplace
Gas water heater*
Gas furnace
Vented gas heater
Gas fireplace logs
Other gas
appliances*
Total
* Do not include direct-vent gas appliances.
Direct-vent draws combustion air from the
outdoors and vents to the outdoors.
Example:
Gas water heater
Vent-free fireplace + __________ Btu/Hr
Total
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: 35,840 Btu/Hr (maximum the
space can support)
40,000 Btu/Hr (actual amount of
Btu/Hr used)
The space in the example on the previous
page is a confined space because the actual
Btu/Hr used is more than the maximum Btu/Hr
the space can support. You must provide addi-
tional 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 8
___________ Btu/Hr
___________ Btu/Hr
___________ Btu/Hr
___________ Btu/Hr
___________ Btu/Hr
+ __________ Btu/Hr
= __________ Btu/Hr
30,000
___________ Btu/Hr
10,000
40,000
= __________ Btu/Hr
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