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Calculating Duct System Length
The recommended duct system is 6" (15.2 cm) round duct with a maximum
length of 35 ft (10.7 m). For the best performance, use no more than three 90°
elbows.
To calculate the length of the system you need, add the equivalent feet
(meters) for each duct piece used in the system.
Duct Piece
6" (15.2 cm) Round
45° elbow
2.5 ft (0.8 m)
90° elbow
5.0 ft (1.5 m)
Maximum equivalent duct length is 35 ft (10.7 m).
Example Duct System -
6" (15.2 cm)
90˚ elbow
Wall cap
6 ft (1.8 m)
3 ft
(0.93 m)
Maximum length
= 35 ft (10.7 m)
1 - 90° elbow
1 – wall cap
6 ft (1.8 m) straight
3 ft (0.9 m) straight
= 5.0 ft (1.5 m)
= 0.0 ft (0.0 m)
= 6.0 ft (1.8 m)
= 3.0 ft (0.9 m)
System length
= 14.0 ft (4.3 m)
