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Installation instructions
Maximum length of exhaust duct
Preferred 4” Hoods
When you have a 4” (100 mm) Hood
Maximum length of 4” diameter metal duct.
Number of 90˚
elbows/bends
Rigid
Thick Wall Flexible Metal
(fully extended)
0 64 ft 19.5 m 36 ft 10.9 m
1 54 ft 16.5 m 31 ft 9.4 m
2 44 ft 13.4 m 27 ft 8.2 m
3 35 ft 10.6 m 25 ft 7.6 m
4 27 ft 8.2 m 23 ft 7.0 m
Acceptable 2 ½” Hood
When you have a 2 ½” (60 mm) Hood
Maximum length of 4” diameter metal duct.
Number of 90˚
elbows/bends
Rigid
Thick Wall Flexible Metal
(fully extended)
0 58 ft 17.6 m 28 ft 8.5 m
1 48 ft 14.6 m 23 ft 7.0 m
2 38 ft 11.5 m 19 ft 5.7 m
3 29 ft 8.8 m 17 ft 5.1 m
4 21 ft 6.4 m 15 ft 4.5 m
For exhaust systems not covered by the exhaust duct length charts (such as multiple unit
hook-ups, plenums, and power-assist fans), call our Customer Care Center:
TOLL FREE 1 888 9 FNP USA (1 888 9 367 872).
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