Pre-Installation Items
6
All Combustion Air from outdoors
through; One Permanent Air Openings
Fig. 2:
All Combustion Air from Outdoors
Through Ventilated Attic
Fig. 3:
All Combustion Air from Outdoors
through Horizontal Ducts
Fig. 4:
Two Permanent Openings Method.
Two permanent openings, one commencing within 12 in.
of the top and one commencing within 12 in. of the bot-
tom of the enclosure, shall be provided. The openings
shall communicate directly, or by ducts, with the out-
doors or spaces that freely communicate with the out-
doors, as follows:
-
Where directly communicating with the outdoors
or where communication to the outdoors is
through vertical ducts, each opening shall have
a minimum free area of 1 sq. in./4000 Btu/hr of
total input rating of all equipment in the enclo-
sure. See Fig.3.
-
Where communicating with the outdoors is
through horizontal ducts, each opening shall
have a minimum free area of not less than 1
sq.in./2000 Btu/hr of total input rating of all
equipment in the enclosure. See Fig. 4.
