Air Directly Through An Exterior Wall; Alternate Method Of Providing Air From Outside; Air From Inside; Installation In An Unconfi Ned Space - Nordyne 045C-23ASA Installation Instructions Manual

Air Directly Through An Exterior Wall

If combustion air is provided directly through an exterior
wall, the two openings must each have free area of at
least one square inch per 4,000 Btuh of total appliance
input (Figure 4).
12" Max
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See
Note
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Water Heater
12" Max
Total Input Rating
(Btuh)
40,000
60,000
80,000
100,000
120,000
140,000
160,000
Figure 4. Combustion Air Drawn from Outside
Through an Exterior Wall

Alternate Method of Providing Air from Outside:

If acceptable under local Codes, it is permitted to
provide outside air using one opening (See NFGC).
Generally, confi ned spaces must have two openings
in the space for combustion air. One opening must
be within 12 inches of the ceiling, and the other
must be within 12 inches of the fl oor. However, an
alternative method recently adopted by the NFGC
uses one opening within 12 inches of the top of the
space. This method may be used if it is acceptable
to the local codes.
The following conditions must be met:
1. The opening must start within 12" of the top of the
structure and connect with the out of doors through
vertical or horizontal ducts or be ducted to a crawl
or attic space that connects with the out of doors.
2. The opening must have a minimum free area of 1
sq. in. per 3,000 Btu per hour of the total input rating
of all equipment located in the enclosure.
3. The free area must not be less than the sum of all
the areas of the vent connectors in the enclosure.
8
Vent or
Chimney
NOTE: Each opening
to outside must be at
Furnace
least 1 sq. in. per
4,000 Btuh of total
input rating.
Minimum Free Area Round Duct
(Each Opening) Diameter
10 sq. In
15 sq. In
20 sq. In
25 sq. In
30 sq. In
35 sq. In
40 sq. In

Air From Inside

If combustion air is taken from the heated space, the two
openings must each have a free area of at least one square
inch per 1,000 Btuh of total input of all appliances in the
confi ned space, but not less than 100 square inches of
free area (Figure 5). For example, if the combined input
rate of all appliances is less than or equal to 100,000
Btuh, each opening must have a free area of at least 100
square inches. If the combined input rate of all appliances
is 120,000 Btuh, each opening must have a free area of
at least 120 square inches.
NOTES:
Each opening must
be at least 100 sq. in.
or 1 sq. in. per 1,000
Btuh of total input rating,
whichever is greater.
Openings must start at
4 inches
no more than 12 inches
5 inches
from the top and bottom
of the enclosure.
5 inches
6 inches
6 inches
Total Input Rating
7 inches
(Btuh)
8 inches
40,000
60,000
80,000
100,000
120,000
140,000
160,000
Figure 5. Combustion Air Drawn from Inside
Installation In An Unconfi ned Space
An unconfi ned space is an area including all rooms not
separated by doors with a volume greater than 50 cubic
feet per 1,000 Btuh of the combined input rates of all
appliances which draw combustion air from that space.
In general, a furnace installed in an unconfi ned space will
not require outside air for combustion. However, in homes
built for energy effi ciency (low air change rates), it may
be necessary to provide outside air to ensure adequate
combustion and venting, even though the furnace is located
in an unconfi ned space. See example.
A space with a water heater rated at 45,000 Btuh
input and a furnace rated at 75,000 Btuh requires a
volume of 6,000 cubic feet [50 x (45 + 75) = 6,000] to
be considered unconfi ned. If the space has an 8 foot
ceiling, the fl oor area of the space must be 750 square
feet (6,000 / 8 = 750).
Vent or
Chimney
12" Max.
Furnace
See Notes
Water
Heater
Minimum Free Area
(Each Opening)
100 sq. In
100 sq. In
100 sq. In
100 sq. In
120 sq. In
140 sq. In
160 sq. In
Example:
See
Notes
12" Max.
Round Duct
Diameter
12 inches
12 inches
12 inches
12 inches
13 inches
14 inches
15 inches