Air For Combustion And Ventilation - Desa GWN6 Installation Manual

AIR FOR COMBUSTION AND VENTILATION

DETERMINING FRESH-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. (6.1 m) (length) x
16 ft. (4.88 m) (width) x 8 ft. (2.44 m) (ceiling
height) = 2560 cu. ft. (72.49 m
space)
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 determine
the maximum Btu/Hr the space can support.
________ (volume of space) x 20 = (Maxi-
mum Btu/Hr the space can support)
Example: 2,560 cu. ft. (72.49 m
space) x 20 = 51,200 (maximum Btu/Hr the
space can support)
3. Add the Btu/Hr of all fuel burning appliances
in the space.
Vent-free heater
Gas water heater*
Gas furnace
Vented gas heater
Gas fireplace logs
Other gas appliances* + _________Btu/Hr
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 heater
Total
4. Compare the maximum Btu/Hr the space
can support with the actual amount of Btu/Hr
used.
_______ Btu/Hr (maximum space can
support)
_______ Btu/Hr (actual Btu/Hr used)
6
Continued
) (volume of
3
) (volume of
3
__________Btu/Hr
__________Btu/Hr
__________Btu/Hr
__________Btu/Hr
__________Btu/Hr
= _________Btu/Hr
50,000
__________Btu/Hr
10,000
+ _________Btu/Hr
60,000
= _________Btu/Hr
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Example: 51,200 Btu/Hr (maximum the space
can support)
60,000 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, page 7.
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 oper-
ated is smaller than that defined
as an unconfined space or if the
building is of unusually tight
construction, provide adequate
combustion and ventilation air
by one of the methods described
in the National Fuel Gas Code,
ANSI Z223.1/NFPA 54, Air for
Combustion and Ventilation or
applicable local codes.
VENTILATION AIR
Ventilation Air From Inside Building
This fresh air would come from an adjoin-
ing unconfined space. When ventilating to
an adjoining unconfined space, you must
provide two permanent openings: one within
12" (30.5 cm) of the ceiling and one within
12" (30.5 cm) of the floor on the wall con-
necting the two spaces (see options 1 and 2,
Figure 2, page 7). You can also remove door
into adjoining room (see option 3, Figure 2,
page 7). Follow the National Fuel Gas Code,
ANSI Z223.1/NFPA 54, Air for Combustion
and Ventilation for required size of ventilation
grills or ducts.
117001-01E