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Instructions for Installation (cont'd)
b. ALl. AIR FROM OUTDOORS: (see Figures 3-5) 3. When communicating with the outdoors through horizon-
The confined space shall be provided with two permanent tal ducts, each opening shall have a minimum free area of 1
openings, one commencing within 12 inches of the top and square inch per 2,000 BTU per hour of total input rating of
one commencing within 12 inches from the bottom of the all equipment in the enclosure. (See Figure 5.)
enclosure. The openings shall communicate directly, or by
ducts, with the outdoors or spaces (crawl or attic) that
freely communicate with the outdoors.
Figure 5 I
IFigure3I
4. When ducts are used, they shall be of the same cross-sec-
N-T. INLETAIR VENTILAT_N
tional area as the free area of the openings to which they
connect. The minimum short side dimension of rectangular
1.When directly communicating with the outdoors, each air ducts shall not be less than 3 inches. (See Figure 5.)
opening shall have a minimum free area of 1 square inch
per 4,000 BTU per hour of total input rating of all equip- 5. Louvers and Grilles: In calculating free area, consideration
ment in the enclosure. (See Figure 3.) shall be given to the blocking effect of louvers, grilles or
screens protecting openings. Screens used shall not be
2. When communicating with the outdoors through vertical smaller than 1/4inch mesh. If the free area through a design
ducts, each opening shall have a minimum free area of 1 of louver orgrille is known, it should be used in calculating
square inch per 4,000 BTU per hour of total input rating of the size opening required to provide the free area specified.
all equipment in the enclosure. (See Figure 4.) If the design 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 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
Figure I special to unsatisfactory operation
4
attention avoid
of
installed gas utilization equipment.
12