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Installation Instructions (cont'd)
Combustion Air and Ventilation
for Appliances Located in
Unconfined Spaces
Uncunl_ed Spac* is a space whose volum_ is not lessthan 50
cubic feet per 1,000 Btu per hour of the aggregate input rating
of all appliances installed in that space. Rooms communicating
directly with the space in which the appliances am installeff,
through openings not furnished with doors, are considered a
part of the unconfined space
In unconfined spaces in buildings, infiltration may be adequate
to provide air for combustion, ventilation and dilution of flue
gases. However, in buildings of tight construction (for example,
weather stripping, heavily insulated, caulked, vaporbarrier, etc.)
additional air may need to be provided using the methods
described in Combustion Air and Ventilation for Appliances
Located in Confined Spaces, b.
Combustion Air and Ventilation
for Appliances Located in
Confined Spaces
Confined Space is a space whose volume is less than 50 cubic
feet per 1,000 Btu per hour of the aggregate input rating of all
appliances installed in that space.
a. ALL AIR FROM INSIDE BUILDINGS:
(See Page 9 Figure 1, and Figure 2 below)
The confined space shall be provided with two permanent
o_enings communicating directly with an additional room(s)
or sufficient volume so that the combined volume of all
spaces meets the criteria for an unconfined space. The total
input of all gas utilization equipment installed in the com-
bined space shall be considered in making this determination.
Each opening shall have a minimum flee area of one square
inch per 1,000 BTU per hour of the total input rating of all
gas utilization equipment in the confined space, but not less
than 100 square inches. One opening shall commence within
12 inches of the top and one commencing within 12 inches
of the bottom of the enclosure.
b. ALL AIR FROM OUTDOORS: (seeFigures3-5)
The confined space shall be provided witl_ two permanent
openings, one commencing within 12 inches of the top and
one commencing within 12 inches from the bottom of the
enclosure. The openings shall communicate directly, or by
ducts, with the outdoors or spaces (crawl orattic) that freely
communicate with the outdoors.
Figure 3 ]
10
1. When directly communicatingwith the outdoors, each open-
ing shall have a minimum freearea of 1square inch per 4,000
BTU per hour of total input raring ofall equipment in the
enclosure. (SeeFigure 3.)
2. When communicating with the outdoors through vertical
ducts, each opening shall have a minimum free area of 1
square inch per 4,000 BTU per hour of total input ratin_of
all equ pment in the enclosure. (See Figure 4.) v
ot_1_1 OR OAS VEK'g
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tan OUTLET
WATE_ F_ATEm
FUflgaOE
_ AJn DUCT
8m_ V aoom _o_)
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3. When communicating with the outdoors through horizontal
ducts, each opening shall have a minimum free area of 1
_uare inch per 2,000 BTU per hour of total input rating of
equipment in the enclosure. (See Figure 5.)
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4. When ducts are used, they shall be of the same cross-sectional
area as the free area of the openings to which they connect.
The minimum short side dimension of rectangular air ducts
shall not be less than 3 inches. (See Figure 5.)
,
Louvers and Grilles: In calculating free area, consideration
shall be given to the blocking effect of louvers, grilles or
screens protecting openings. Screens used shall not be smaller
than ΒΌ inch mesh. If the free area through a design of louver
or grille is known, it should be used in calculating the size
o,penin, g required to .provide the free. area specified. If the
aesLgn and free area is not known, It may be assumed that
wood louvers will be 20-25 percent free area and metal louvers
and grilles will have 60-75 percent free area. Louvers and
grilles shall be fixed in the open position or interlocked with
the .equipment so. that they are opened automatically during
eqmpment operauon.
6. Special Conditions Created by Mechanical Exhausting or
Fireplaces: Operation of exhaust fans, ventilation systems
domes dryers or fireplaces may create conditions requiring
special attention to avoid unsatisfactory operation of installed
gas utilization equipment.
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