Dunkirk XEB-4 - Ventilation and Combustion Air; Combustion Air Requirements; Air Infiltration Table

6
FRESH AIR FOR COMBUSTION
FRESH AIR DUCT CAPACITIES (1 Square inch per 4,000 Btuh)
Fresh Air
Duct Size
100% Free Area
1/4” Wire Mesh
75% Free Area
Metal Louvers
25% Free Area
Wood Louvers
3” x 12” 144,000 108,000 36,000
8” x 8” 256,000 192,000 64,000
8” x 12” 384,000 288,000 96,000
8 ½” x 16” 512,000 384,000 128,000
FRESH AIR DUCT CAPACITIES (1 Square inch per 2,000 Btuh)
Fresh Air
Duct Size
100% Free Area
1/4” Wire Mesh
75% Free Area
Metal Louvers
25% Free Area
Wood Louvers
3” x 12” 72,000 54,000 18,000
8” x 8” 128,000 96,000 32,000
8” x 12” 192,000 144,000 48,000
8 ½” x 16” 256,000 192,000 64,000
B. All Air From Outdoors: The confined
space shall communicate with the outdoors in
accordance with methods 1 or 2. The minimum
dimension of air openings shall not be less than
3 in. Where ducts are used, they shall be of the
same cross-sectional area as the free area of the
openings to which they connect.
1. Two permanent openings, one commencing within
12 inches of the top, and one commencing within
12 inches of the bottom, of the enclosure shall
be provided. The openings shall communicate
directly, or by the ducts, with the outdoors or
spaces (crawl or attic) that freely communicate
with the outdoors.
a) Where directly communicating with the outdoors
or where communicating to the outdoors
through vertical ducts, each opening shall have
a minimum free area of 1 sq. in, per 4000 Btu
per hour of total input rating of all equipment
in the enclosure (see Figure #3B).
Figure #3B
b) Where communicating with the outdoors
through horizontal ducts, each opening shall
have a minimum free area of 1 area of sq. in. per
2000 Btu per hour of total rating of all equipment
in the enclosure (see Figure #3C).
Figure #3C
2. One permanent opening commencing with
12 inches of the top of the enclosure, shall be
permitted where the equipment has clearance
of at least 1 inch from the sides and back and 6
inches form the front of the appliance. The opening
shell directly communicate with the outdoors or
shall communicate through a vertical or horizontal
duct to the outdoors or to a crawl space or attic
that freely communicate with the out doors, and
shall have a minimum free area of: