Step 2: Prepare The Venting System; Standard Fittings; Duct Length - Sears 721.80513 Installation Instructions Manual

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.

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.
Below are the standard fittings and their equivalent length in feet.
3 1/4" x 10" to 6" = 5 ft.
90˚elbow = 10 ft
To calculate the equivalent length of each duct piece used, see the examples below.
For 3-1/4" x 10" SYSTEMS
1 3-1/4" x 10" 90° elbow
1 Wall Cap
8 feet straight duct
TOTAL LENGTH
STEP 2:
PREPARE THE VENTING SYSTEM
3 1/4" x 10" roof cap = 24 ft
3 1/4" x 10" wall cap
= 40 ft
= 25 ft.
= 40 ft.
=
= 73 ft.
45˚elbow = 5 ft
Figure 9
Examples
For 6" ROUND SYSTEMS
1 transition
2 90° elbows
1 Wall Cap
8 ft.
8 feet straight
TOTAL LENGTH
3 1/4" x 10" 90˚ elbow = 25 ft
3-1/4" x 10" flat elbow
= 10 ft
= 5 ft.
= 20 ft.
= 40 ft.
= 8 ft.
= 73 ft.
9