Install Instructions

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2.0 Combustion Air Venting
2.4.2.2 Two Permanent Openings Method
Two permanent openings, one commencing
within 12 in. of the top and one commencing
within 12 in. of the bottom of the enclosure,
shall be provided. The openings shall commu-
nicate directly, or by ducts, with the outdoors
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 rat-
ing of all equipment in the enclosure.
See Fig.3.
- Where communicating with the out-
doors 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 equip-
ment in the enclosure. See Fig. 4.
All Combustion Air from Outdoors
Through One Permanent Air
Opening
Fig. 2:
All Combustion Air from Outdoors
Through Ventilated Attic
Fig. 3:
All Combustion Air from Outdoors
Through Horizontal Ducts
Fig. 4: