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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 pet 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, ate 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 exampl€,
weather stripping, heavily insulated, caulked, vapor barri€r, etc.),
additional air may need to be provided using the methods
described in Combustion Ait and Ventilation t'orAppliances
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 Bm per hour of the aggregate input ratingof all
appliances installed in that space.
a. ALL AIR FROM INSIDE BUILDINGS.
(See Page9 Figure 1,and Figure2 below)
The €onfined space shall be provided with two permanent
openings communicating directlywith an additional room(s)
of suiTlcient 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 Mall be consideredin making this determination.
Each opening shall have a minimum free areaof 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.
1. When directly communicating with the outdoors, each open-
ing shallhave a minimum free areaof 1 square inchper 4,000
BTU per hour of total input rating ofall equipment in the
€ndosure. (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 endosure. (See Figure 4.)
_L_IEy Off Otd VEIcr
V_Tga_'flO_ LO_EF*O
Figure 4 ]
3. When communicating with the outdoors through horizontal
ducts, each opening shall have a minimum free area of l
alsctuareinch per 2,000 BTU per hour of total input rating of
equipment in the enclosure. (SeeFigure 5.)
Figure 5 ]
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 rectangularair ducts
shall not be lessthan 3 inches. (SeeFigure 5.)
b. ALL AIR FROM OUTDOORS: (seeFigures3-5)
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 orspaces (crawl or attic) that freely
communicate with the outdoors.
IFI re']
10
5. Louvers and Grilles: In calculating free area, consideration
shall be given to the blocking €ffect of louvers, grilles or
screens protecting openings. Screens used shall not be smaller
than ¼inch 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 be 20-25 percent free areaand 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 automaticallyduring
equipment operation.
6. Special Conditions Created by Mechanical Exhausting or
Fireplaces: Operation of €xhaust fans, ventilation systems,
clothes dryers or fireplaces may create conditions requiring
special attention to avoid unsatisfactory operation of installed
gasutilization equipment.