Allied Air A96US2V Installation Instructions Manual page 8

Air from Outside
If air from outside is brought in for combustion and
ventilation, the confined space shall be provided with two
permanent openings. One opening shall be within 12" (305
mm) of the top of the enclosure and one within 12" (305
mm) of the bottom. These openings must communicate
directly or by ducts with the outdoors or spaces (crawl or
attic) that freely communicate with the outdoors or indirectly
through vertical ducts. Each opening shall have a minimum
free area of 1 square inch per 4,000 Btu (645 mm² per .59
kW) per hour of the total input rating of all equipment in the
enclosure (See Figures 5 and 6). It is also permissible to
bring air for combustion from a ventilated attic (Figure 8) or
ventilated crawl space (Figure 9).
Equipment in Confined Space - All Air from Outside
(Inlet Air from Crawl Space and Outlet Air to Ventilated Attic)
Figure 5
When communicating with the outdoors through horizontal
ducts, each opening shall have a minimum free area of 1
square inch (645 mm²) per 2,000 Btu (.56 kW) per hour of
the total input rating of all equipment in the enclosure. See
Figure 7.
Equipment in Confined Space - All Air from Outside
(All Air through Ventilated Attic)
Page 8 of 80
Figure 6
Equipment in Confined Space - All Air from Outside
Equipment in Confined Space
(Inlet Air from Ventilated Attic and Outlet Air to Outside)
Equipment in Confined Space
(Inlet Air from Ventilated Crawlspace and Outlet Air to Outside)
Issue 1621
Figure 7
Figure 8
Figure 9
507404-04