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INSTALLATION
STEP 2: PREPARE THE VENTING SYSTEM
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's sticking.
DUCT LENGTH
The total length of the duct system, including straight duct, elbows, transitions, and wall or roof caps must not
exceed the equivalent of 140 feet.
For best performance, do not use more than three 90 degree elbows, and keep length as short as possible.
Below are the standard fittings and their equivalent length in feet.
3 1/4"x10"
to 6"=5ft.
2
3 1/4"x!0" roof
cap=24ft.
3
3 1/4"x!0" 90°
elbow=25ft.
4
90° elbow
=lOft.
3 !/4"x10"
wall cap
=40ft.
6
45 °elbow
=5ft.
7
3 1/4"x10"
fiat elbow
=lOft.
Figure 9
To calculate the equivalent length of each ductpiece used, see the examples below.
I
Examples
For 3 1/4"x10" SYSTEMS
3 1/4"x10" _ 6ft. _ wall cap
90 elbow _.,_ I [_
H2_t.
1-3 1/4" x 10" 90 °elbow = 25 ft.
1-Wall Cap 40 ft.
8 feet straight duct 8 ft.
TOTAL LENGTH 73 ft.
For 6" ROUND SYSTEMS
wall cap
90 elbows _ 6ft.
transi_ / "---11¢
1-transition = 5 ft.
2-90 °elbows = 20 ft.
1-Wall Cap = 40 ft.
8 feet straight = 8 ft.
TOTAL LENGTH = 73 ft.
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