Desa CDR3924NT Owner's Operation And Installation Manual page 7

AIR FOR COMbUSTION AND VENTILATION
Example:
Gas water heater
Vent-free heater
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: 51,200 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 sup-
port. 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 adjoin-
ing room or add ventilation grills between
rooms. See Ventilation Air From Inside
Building.
B. Vent room directly to the outdoors. See
Ventilation Air From Outdoors.
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 maxi-
mum Btu/Hr the space can support, the space is
an unconfined space. You will need no additional
fresh air ventilation.
WARNING: If the area in which
the heater may be operated does
not meet the required volume for
indoor combustion air, combus-
tion 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.
vENTILATION AIR
Ventilation Air From Inside Building
This fresh air would come from an adjoining un-
confined space. When ventilating to an adjoining
unconfined space, you must provide two perma-
nent openings: one within 12" of the ceiling and
122270-01D
Continued
40,000
__________Btu/Hr
39,000
+ _________Btu/Hr
79,000
= _________Btu/Hr
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one within 12" of the floor on the wall connecting
the two spaces (see options 1 and 2, Figure 2).
You can also remove door into adjoining room
(see option 3, Figure 2). Follow the National
Fuel Gas Code, ANSI Z223.1/NFPA 54, Air for
Combustion and Ventilation for required size of
ventilation grills or ducts.
Ventilation
Grills Into
Adjoining
Or
Room,
Remove
Option 1
Door into
Adjoining
Room,
Option
3
Figure 2 - Ventilation Air from Inside
Building
ventilation Air From Outdoors
Provide extra fresh air by using ventilation
grills or ducts. You must provide two perma-
nent openings: one within 12" of the ceiling
and one within 12" of the floor. Connect these
items directly to the outdoors or spaces open
to the outdoors. These spaces include attics
and crawl spaces. Follow the National Fuel
Gas Code, ANSI Z223.1/NFPA 54, Air for
Combustion and Ventilation for required size
of ventilation grills or ducts.
IMPORTANT: Do not provide openings for
inlet or outlet air into attic if attic has a thermo-
stat-controlled power vent. Heated air entering
the attic will activate the power vent.
Outlet
Air
Outlet
Air
Inlet
Air
Inlet Air
Figure 3 - Ventilation Air from Outdoors
12"
Ventilation Grills
Into Adjoining Room,
Option 2
12"
Ventilated
Attic
To Attic
To
Crawl
Space
Ventilated
Crawl Space
7