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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.
Below are the standard fittings and their equivalent length in feet.
To calculate the equivalent length of each duct piece used, see the examples below.
STEP 2:
PREPARE THE VENTING SYSYTEM