Design Dynamics VF-18P-MHD Gas Heater User Manual


 
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116986-01H 7
AIR FOR COMBUSTION AND VENTILATION
Continued
Example:
Gas water heater __________Btu/Hr
Vent-free replace+ __________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 (max the space can support)
______Btu/Hr (actual amount 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 conned space
because the actual Btu/Hr used is more than the
maximum Btu/Hr the space can support. 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 unconned 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 replace, if lower Btu/Hr
size makes room unconned.
If the actual Btu/Hr used is less than the maxi-
mum Btu/Hr the space can support, the space is
an unconned space. You will need no additional
fresh air ventilation.
WARNING: If the area in which
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
-


 National Fuel
Gas Code, ANSI Z223.1/NFPA 54,
the International Fuel Gas Code,
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

This fresh air would come from an adjoining
unconned space. When ventilating to an
adjoining unconned space, you must provide
two permanent openings: one within 12" of the
ceiling and one within 12" of the oor on the
wall connecting the two spaces (see options
1 and 2, Figure 2). You can also remove door
Figure 2 - Ventilation Air from Inside
Building
Or
Remove
Door into
Adjoining
Room,
Option
3
V e ntilation Grills
Into Adjoining Room,
Option 2
V e ntilation
Grills
Into Adjoining
Room,
Option 1
12"
12"
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.
Figure 3 - Ventilation Air from Outdoors
Outlet
Air
V entilated
Attic
Outlet
Air
Inlet
Air
Inlet Air
V entilated
Crawl Space
T o
Crawl
Space
T o Attic
40,000
33,000
73,000

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 oor. 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.