Installation Instructions
6
Advance Planning
DUCT FITTINGS
Total
Equivalent Quantity Equivalent
Duct Piece Dimensions Length* Used Length
Round, 1 ft.
straight (per foot
length)
1 ft.
3-1/4" x 12" (per foot
straight length)
90° elbow 17 ft.
45° elbow 10 ft.
3-1/4" x 12"
90° elbow 43 ft.
3-1/4" x 12"
45° elbow 26 ft.
3-1/4" x 12"
90° at elbow 102 ft.
8" round to
3-1/4" x 12" transition 2 ft.
3-1/4" x 12"
to 8" round transition 5 ft.
8" round
to 3-1/4" x 12"
transition 90° elbow 6 ft.
3-1/4" x 12" to 8"
round transition 90° elbow 13 ft.
Round
wall cap
with damper 32 ft.
3-1/4" x 12" wall cap
with damper 75 ft.
Round
roof cap 44 ft.
Use this chart to compute maximum
permissible lengths for duct runs to
outdoors.
NOTE: Do not exceed maximum permissible
equivalent lengths!
Maximum duct length: 100 ft. for range hoods.
Flexible ducting:
If exible metal ducting is used, all
the equivalent feet values in the table
should be doubled. The exible metal
duct should be straight and smooth and
extended as much as possible.
Do NOT use exible plastic ducting.
Total Duct Run
NOTE: Any home ventilation system, such as a
ventilation hood, may interrupt the proper ow of
combustion air and exhaust required by replaces,
gas furnaces, gas water heaters and other naturally
vented systems. To minimize the chance of inter-
ruption of such naturally vented systems, follow the
heating equipment manufacturer’s guidelines and
safety standards such as those published by NFPA
and ASHRAE.
* Actual length of straight duct plus duct tting equivalent. Equivalent
length of duct pieces are based on actual tests conducted by GE
Evaluation Engineering and reect requirements for good venting
performance with any ventilation hood.
This Hood Must
Use 8" Round Duct.
It Can Transition to
3-1/4" x 12" Duct.