Installation Guide

8
Figure5.CombustionAirDrawnfromOutside
ThroughHorizontalDucts
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12" Max
12" Max
Furnace
Vent or
Chimney
Water Heater
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Air Duct
Air Duct
NOTE: Each
opening to
outside must
be at least 1
sq. in. per 2,000
Btuh of total
input rating.
See
Note
TotalInputRating
(Btuh)
MinimumFreeArea
(EachOpening)
RoundDuct
Diameter
40,000 10 in
2
5 inches
60,000 15 sin
2
6 inches
80,000 20 in
2
7 inches
100,000 25 in
2
8 inches
120,000 30 in
2
9 inches
140,000 35 in
2
10 inches
160,000 40 in
2
10 inches
Figure6.CombustionAirDrawnfromOutside
ThroughanExteriorWall
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12" Max
12" Max
Furnace
NOTE: Each opening
to outside must be at
least 1 sq. in. per
4,000 Btuh of total
input rating.
Vent or
Chimney
Water Heater
See
Note
TotalInputRating
(Btuh)
MinimumFreeArea
(EachOpening)
RoundDuct
Diameter
40,000 10 in
2
4 inches
60,000 15 in
2
5 inches
80,000 20 in
2
5 inches
100,000 25 in
2
6 inches
120,000 30 in
2
6 inches
140,000 35 in
2
7 inches
160,000 40 in
2
8 inches
Figure4.CombustionAirDrawnfromOutside
ThroughVerticalDucts
Inlet Air Duct must
be at least 1 sq. in.
per 4,000 Btuh of
total input rating.
Inlet and Outlet
Ducts must
extend above
attic insulation.
Outlet Air Duct must
be at least 1 sq. in.
per 4,000 Btuh of
total input rating.
Ventilation Louvers at
each end of attic
Attic
Insulation
12" Max
Furnace
Water
Heater
Vent or
Chimney
TotalInputRating
(Btuh)
MinimumFreeArea
(EachOpening)
RoundDuct
Diameter
40,000 100 in
2
12 inches
60,000 100 in
2
12 inches
80,000 100 in
2
12 inches
100,000 100 in
2
12 inches
120,000 120 in
2
13 inches
140,000 140 in
2
14 inches
160,000 160 in
2
15 inches
Figure3.CombustionAirDrawnfromaCrawl
SpaceorVentedAttic
Attic
Insulation
Crawl Space
Ventilated Louvers for
unheated crawl space
Inlet air duct must be at
least 1 sq. in. per 4,000
Btuh of total input rating.
Outlet air duct must be
at least 1 sq. in. per
4,000 Btuh of total
input rating. Must
extend above attic
insulation
Water
Heater
Furnace
Vent or
Chimney
Ventilation louvers
at each end of attic
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
1in
2
per 4,000 Btuh of total appliance input. See Figure 6.