STANDARD FITTINGS
NOTE: If the existing duct is round, you must use a rectangular-to-round adapter, with a rectangular 3" extension
duct installed between the damper assembly and the adapter to prevent the exhaust damper sticking.
Below are the standard fittings and their equivalent length in feet.
DUCT LENGTH
The total length of the duct system, including straight duct, elbows, transitions, wall or roof caps
must not
exceed the equivalent of 140 feet.
For best performance, do not use more than three 90 degree elbows.
To calculate the equivalent length of each duct piece used, see the examples below.
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FOR PROPER VENTING SEARS
RECOMMENDS
Examples
FOR 3 1/4"x10" SYSTEMS
6" to 3 1/4" x 10" transition
1-90˚ elbow
Wall cap
8 feet straight duct
TOTAL LENGTH
3 1/4" x 10" to 6" transition
2-90 degree elbows
Wall cap
8 feet straight
TOTAL LENGTH
FOR 6" ROUND SYSTEMS
6ft.
2ft.
2ft.
3 1/4"x10"
90˚ elbow
wall cap
6ft.
90˚ elbows
wall cap
= 25 ft.
= 40 ft.
= 8 ft.
= 73 ft.
= 5 ft.
= 20 ft.
= 40 ft.
= 8 ft.
= 73 ft.
3 1/4"x10" to 6" = 5ft.
90˚ elbow = 10ft.
45˚ elbow = 5ft.
3 1/4"x10" wall cap
= 40ft.
3 1/4"x10" flat elbow
= 10ft.
3 1/4"x10" roof cap = 24ft.
3 1/4"x10" 90˚ elbow = 25ft.
1
4
5
6
7
2
3
Figure 7
