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Installation (Combustion Air Supply) continued-
All Air From Inside the Building: The confined space must 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 combined space must be considered in making this determination. Each
opening must have a minimum free area of 1 square inch per 1000 BTU (6.5
cm
2
/0.29 kw) per hour of the total input rating of all gas utilization equipment in
the confined space, but not less than 100 square inches (645 cm
2
). One opening
must be within 12 inches (31 cm) of the top and one within 12 inches (31 cm) of
the bottom of the enclosure.
All Air From Outdoors: The confined space must be provided with two
permanent openings, one commencing within 12 inches (31 cm) of the top and
one commencing within 12 inches (31 cm) from the bottom of the enclosure. The
openings must communicate directly, or by ducts, with the outdoors or spaces
(crawl or attic) that freely communicate with the outdoors.
1. When directly communicating with the outdoors, each opening must have a
minimum free area of 1 square inch per 4000 BTU (6.5 cm
2
/1.2 kw) per hour
of total input rating of all equipment in the enclosure.
2. When communicating with the outdoors through vertical ducts, each opening
must have a minimum free area of 1 square inch per 4000 BTU (6.5 cm
2
/1.2
kw) per hour of total input rating of all equipment in the enclosure.
3. When communicating with the outdoors through horizontal ducts, each
opening must have a minimum free area of 1 square inch per 2000 BTU (6.5
cm
2
/0.6 kw) per hour of total input rating of all equipment in the enclosure.
4. When ducts are used, they must be of the same cross-sectional area as the
free area of the openings to which they connect. The minimum dimension of
rectangular air ducts must be not less than 3 inches (7.5 cm).
Specially Engineered Installations
The requirements noted under CONFINED SPACES above must not necessarily
govern when special engineering, approved by the authority having jurisdiction,
provides an adequate supply of air for combustion, ventilation, and dilution of flue
gases.
Water Connections
INTERNET VERSION FOR REFERENCE ONLY