Installation / Operation Instruction Manual

17
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 in
2
/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 in²
(645 cm
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
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 communicating with the outdoors through vertical ducts, each
opening must have a minimum free area of 1 in
2
/4000 BTU/hr 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 in
2
/2000 BTU/hr 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 must be not less than 3 inches (8 cm).
Provide one permanent opening, commencing within 12 in (31 cm) of the top of
the enclosure. The appliance shall 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 in
2
/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.