Desa VML27NR Operation And Installation Manual page 7

AiR FoR CoMBuStion
And VEntiLAtion
Continued
Example: Space size 20 ft. (length) x 16 ft.
(width) x 8 ft. (ceiling height) = 2,560 cu. ft.
(volume of 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. (volume of 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 fireplace
Gas water heater*
Gas furnace
Vented gas heater
Gas fireplace logs
Other gas appliances* + __________ Btu/Hr
Total
* Do not include direct-vent gas appliances. Di-
rect-vent draws combustion air from the outdoors
and vents to the outdoors.
Example:
Gas water heater
Vent-free fireplace
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)
73,000 Btu/Hr (actual amount of
Btu/Hr used)
The space in the example is a confined space because
the actual Btu/Hr used is more than the maximum
Btu/Hr the space can support. You must provide ad-
ditional fresh air. Your options are as follows:
A. Rework worksheet, adding the space of an adjoin-
ing 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 Ventila-
tion Air From Outdoors.
C. Install a lower Btu/Hr fireplace, if lower Btu/Hr
size makes room unconfined.
111115-01F
__________ Btu/Hr
__________ Btu/Hr
__________ Btu/Hr
__________ Btu/Hr
__________ Btu/Hr
= __________ Btu/Hr
40,000
__________ Btu/Hr
33,000
+ __________ Btu/Hr
73,000
= __________ Btu/Hr
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If the actual Btu/Hr used is less than the maximum
Btu/Hr the space can support, the space is an uncon-
fined 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 Section 5.3
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 permanent
openings: one within 12" of the ceiling and 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, Section 5.3, 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
12"
Ventilation Grills
Into Adjoining Room,
Option 2
12"