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.
31/4" x 10"
to 6"=5ft.
31/4" x 10" roof
cap=24ft.
3
3 1/4" x 10" 90_
elbow=25ft.
90°elbow
=10ft.
3 1/4" x 10"
wall cap
=40ft.
45°elbow
=5ft.
7
3 1/4" x 10"
flat elbow
=10ft.
Figure 10
To calculate the equivalent length of each duct piece used, see the examples below.
For 3 1/4"x10" SYSTEMS
3 1/4"X10" _ 6ft. | wall cap
90° elb°w "_ _ t. I_
1-31/4"x10"90 ° elbow = 25 ft.
1-Wall Cap = 40 ft.
8 feet straight duct = 8 ft.
TOTAL LENGTH = 73 ft.
Exam 3les
For 6"ROUND SYSTEMS
90 ° elbows _ 6ft
transi_ _..._ _,,/wall
1-transition = 5 ft.
2-90 ° elbows = 20 ft.
1-Wall Cap = 40 ft.
8 feet straight = 8 ft.
TOTAL LENGTH
cap
= 73 ft.
-9-
To Next Page
Loading...
Need help?
General
