State Water Heaters 301 Series Instruction Manual page 19

OUTDOOR AIR THROUGH TWO VERTICAL DUCTS
The illustrations shown in this section of the manual are a reference
for the openings that provide fresh air into confined spaces only.
DO NOT refer to these illustrations for the purpose of vent
installation. See
Venting Installation
venting installation instructions.
Figure 12. Two Vertical Ducts
The confined space shall be provided with two permanent vertical
ducts, one commencing within 12 inches (300 mm) of the top and
one commencing within 12 inches (300 mm) of the bottom of the
enclosure. The vertical ducts shall communicate directly with the
outdoors. See .
Figure 12
Each duct opening shall have a minimum free area of 1 square
inch per 4,000 Btu/hr (550 mm
rating of all appliances installed in the enclosure.
When ducts are used, they shall 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 shall be not less than
3 inches (7.62 cm).
(page 21) for complete
per kW) of the aggregate input
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AIR FROM OTHER INDOOR SPACES
Figure 13. Two Permanent Openings
The confined space shall be provided with two permanent
openings, one commencing within 12 inches (300 mm) of the top
and one commencing within 12 inches (300 mm) of the bottom
of the enclosure. See
Figure 13
Each opening shall communicate directly with an additional
room(s) of sufficient volume so that the combined volume of all
spaces meets the criteria for an Unconfined Space.
Each opening shall have a minimum free area of 1 square inch
per 1,000 Btu/hr (2200 mm
of all appliances installed in the enclosure. Each opening shall not
be less than 100 square inches (645 cm
19
.
2 per kW) of the aggregate input rating
).
2