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Installation Instructions (cont'd)
Combustion Air and Ventilation
for Appliances Located in
Unconfined Spaces
Unconfined Space is a space whose volume is not less than 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 are installed,
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, vapor barrier,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 ,
Contined 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
openings communicating directly with an additional room(s)
of 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
th,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.
1.When directly communicating with the outdoors, each open-
ing shall havea minimum freearea of I squareinch per 4,000
BTU per hour of total input ratingof all equipment in the
enclosure. (SeeFigure3.)
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 rating of
all equipment in the enclosure. (SeeFigure4.)
Figure 4 ]
3. When communicating with the outdoors through horizontal
ducts, each opening shall have a minimum free area of 1
_[_uareinch per 2,000 BTU per hour of total input rating of
equipment in the enclosure. (See Figure 5.)
Figure 2 ]
b, ALL AIR FROM OUTDOORS: (seeFigures3-5)
The confined space shall be provided with two permanent
openings, one commencing within 12" of the :op and one
commencing within 12" from the bottom of t!_eenclosure.
The openingsshall communicate directly,or b, ducts,with
the outdoors or spaces (crawl or attic) that free communi-
carewith the outdoors.
Figure 3 I
Figure 5 ]
10
4. When ducts are used, they shall be of the same cross-sectional
area as the flee area of the openings to which they connect.
The minimum short side dimension of rectangular air ducts
shall not be less than 3". (See Figure 5.)
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 ¼-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 f'Lxedin the open position or interlocked with the
equ!pment so that they are opened automatically during
equipment operation,
6. Special Conditions Created by Mechanical Exhausting or
Fireplaces: Operation of exhaust fans, ventilation systems,
clothes dryersor fireplaces may create conditions requiring
specialattention to avoid unsatisfactoryoperationof installed
gasutilization equipment.