LG LMV1680BB Installation Instructions Manual page 9

STEP 2: Prepare The Ventinc/ 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 140 feet.
For best performance, do not use more than three 90 degree elbows, and keep the length as short as possible,
Below are the standard fittings and their equivalent length in feet,
3 1/4"x 10"
to6" =5ft.
2
3 1/4"x 10"roof
cap= 24 ft
3
3 1/4" x 10" 90
elbow = 25 fl
90 elbow
= 10ft
5
3 1/4" x 10"
wall cap
=40ft
45 elbow
=51t
7
3 1/4" x 10"
flat elbow
=10ft
Figure 10
For 3 1/4" x 10" SYSTEMS
3 1/4"x10" wall
90° elbow ,,_- 6ft' -_1 _C_ cap
To calculate the equivalent length of each duct piece used, see the examples below,
I
Examples
For 6" ROUND SYSTEMS
90 'elbows _ 6ft.
transi_ _ ___ 0_ / wall
131/4"x10"90°elbow = 25ft.
1 Wall Cap = 40 ft.
8 feet straight duct = 8 ft.
TOTAL LENGTH = 73 ft.
1 transition = 5 ft,
2 90 ° elbows = 20 ft.
1 Wall Cap = 40 ft,
8 feet straight = 8 ft.
TOTAL LENGTH = 73 ft.
cap
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