www.desatech.com
121486-01F
7
40,000
33,000
73,000
Example:
Gas water heater
___________ Btu/Hr
Vent-free heater
+ __________ Btu/Hr
Total
= __________ Btu/Hr
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)
73,000 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 adjoining 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.
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
unconfined space. When ventilating to an
adjoining unconfined space, you must provide
two permanent openings: one within 12" of the
ceiling and one within 12" of the floor on the
AIR FOR COMBUSTION AND VENTILATION
Continued
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 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.
Figure 2 - Ventilation Air from Inside
Building
Or
Remove
Door into
Adjoining
Room,
Option
3
Ventilation Grills
Into Adjoining Room,
Option 2
Ventilation
Grills Into
Adjoining
Room,
Option 1
12"
12"
Figure 3 - Ventilation Air from Outdoors
Outlet
Air
Ventilated
Attic
Outlet
Air
Inlet
Air
Inlet Air
Ventilated
Crawl Space
To
Crawl
Space
To Attic
