Installation / Operation Instruction Manual

19
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/hr
(2200 mm
2
/kW) of the total input rating of all gas utilization equipment in the
confined space, but not less than 100 in
2
(0.06 m
2
). One opening must be
within 12 in (31 cm) of the top and one within 12 in (31 cm) of the bottom of the
enclosure.
All Air from Outdoors: Provide two permanent openings, one commencing
within 12 in (31 cm) of the top and one commencing within 12 in (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 communicating with the outdoors through vertical ducts, each
opening must have a minimum free area of 1 square inch per 4000 BTU/hr
(550 mm
2
/kW) of total input rating of all equipment in the enclosure.
2. When communicating with the outdoors through horizontal ducts, each
opening must have a minimum free area of 1 square inch per 2000 BTU/hr
(1100 mm
2
/kW) of total input rating of all equipment in the enclosure.
3. 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 cannot be less than 3 in (8 cm).
Provide one permanent opening, commencing within 12 in (31 cm) of the top of
the enclosure. The appliance must have clearance of at least 1 in (3 cm) from
the sides and back and 6 in (16 cm) from the front of the appliance. The
opening must communicate directly or by ducts with the outdoors or spaces
(crawl or attic) that freely communicate with the outdoors and has a minimum
free area of the following:
1. 1 square inch per 3000 BTU/hr (700 mm
2
/kW) of the total input rating of all
appliances located in the enclosure.
2. Not less than the sum of the areas of all vent connectors in the space.
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.