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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.
1D
3 1/4"xlO"[J
to 6"=5ft.
90" elbowO
=10ft.
2D
3 1/4"x10" roofD
cap=24ft,
3[3
3 1/4"x10" 90"0
elbow=25ff,
3 1/4"x10"D
wall capri
--40ft.
6n
45" elbowE]
=5ft.
3 1/4"x10"D
flat elbow n
=10II.
Figure 9
To calculate the equivalent length of each ductpiece used, see the examples below.
For 3 1/4"x10" SYSTEMS
31/4"xW'n _ 6ft._ wallcap
90"elbow I_-'-'_-'- I
Hi"
Exam
1-3 1/4" x 10" 90° elbowD = 25if.E]
1-Wall CapD = 40 ft.D
8 feet straight ductD = 8 ft.D
TOTAL LENGTH = 73 ft.D
D
)les
For 6" ROUND SYSTEMS
90"elbows _
transi_ 6ft. ,--.-_t//wall cap
1-transitionE] = 5 ft.E
2-90 ° elbowsD = 20 ft.r
1-Wall CapD = 40 ft.E
8 feet straight [] = 8 ft.r
TOTAL LENGTH = 73 ft.E
D
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