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Installation InstrudionS (C6nt'd)
Combustion Air and Ventilation
for Appliances Located in
Unconfined Spaces
Unconfined Space isa space whose volume is not less than 50
cubic feet per 1,000 Btu per hour of the aggregate input ratine:
of all appliances installed in that space. Roo--ms-comm'unicatin_
directly with the space in which the appliances are installed,
through openings not furnished with doors, are considered a
,partof the unconfined space
m 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, vapor barrier, etc.),
additional air ma_ 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. . -
ALL AIR FROM INSIDE BUILDINGS.
(See Page 9 Figure 1, and Figure2 below)
The confined space shall be provided with two permanent
oi_enin_s communicating directly with an additional room(s)
or suttlcient 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 free area of one square
inch per 1,000 BTU per hour of the total input rating of all
_s utilization equipment in the confined space, but not less
an 100 square inches. One opening shall commence within
12" of the top and one commencing within 12" of the bot-
tom of the enclosure.
b. ALL AIR FROM OUTDOORS: (see Figures3-5)
The confined space shall be provided with two permanent
openings, one commencing within 12 of the top and one
commenc'ng within 12' from the bottom of the endosure.
The openings shall communicate directly, or by ducts, with
the outdoors or spaces (crawl or attic) that freely communi-
care with the outdoors.
Figure 3 ]
10
1. When directly communicating with the outdoors, each open-
in,shall have a minimum free area of 1square inch per 4,000
BI u per hour of total input rating of all equipment in the
enclosure. (See Figure 3.)
2. When communicating with the outdoors through vertical
ducts, each opening shall have a minimum free area of 1
s_uare inch per 4,000 BTU per hour of total input rating of
all equipment in the enclosure. (See Figure 4.)
Figure 4 ]
CHIMNEy OR _ VEnT
VEhrrUT_O_ LOU_
(each _ oJ a._: I
AIROUTLET
WA'tER _ATE_
I_T AIR DUCT
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.)
_i_caM_v on C,AS_Nr
4. When ducts areused, 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 lessthan 3". (See Figure5.)
.
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 _"mesh. If the free area through a design of louver or
grille is known, it should be used in calculating the size open-
ing required to provide the free area specified. If the design
and free area is not known, it may be assumed that wood lou-
vers 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
equipment operation.
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
gasutilization equipment.