Sears 153.33645 - Manual (Page 10)

1. When directly communicating with the outdoors, each open­
ing shall have a minimum free area of I square inch per 4,000
BTU per hour of total input rating of all equipment in the
enclosure. (Sec Figure 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 rating of
all equipment in the enclosure. (See Figure 4.)
Combustion Air and Ventilation
for Appliances Located in
Unconflned Spaces
Uttconfined 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 unconfmed 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 ia 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 8 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 free area of one square
inch per 1,000 BTU per hour of the total input raring 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 eoramencing within 12 inches
of the bottom of the enclosure.
Installation Instructions (cont’d)
Figure 4
3. When communicating with the outdoors through horizontal
ducts, each opening shall have a minimum free area of 1
square inch per 2,000 BTU per hour of total input rating of
all equipment in the enclosure. {See Figure 5.)
^
Figure 2
Figure S
b. ALL AIR FROM OUTDOORS: (see Fipres 3-5)
The confined space shall be provided with 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 or attic) that freely
communicate with the outdoors.
Figure 3
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.)
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 ¡4 inch mesh. If the free area through a design of louver
or grille is known, it should be used in calculating the size
opening required to provide the free area specified. If the
design and free area is not known, it may be assumed that
wood louvers will he 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,
clothes dryers or fireplaces may create conditions requiring
special attention to avoid unsatisfactory operation of installed
gas utilization equipment.
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