Filter
Top Products
12
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 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.
FIGURE 14.
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.
FIGURE 13.
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 (11 cm
2
/kW) of total input
rating of all equipment in the enclosure, see Figure 14.
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” (76.2 mm),
see Figure 14.
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 1/4 inch (6.4 mm) mesh. If the free area through