DUCT FITTINGS
This Hood Must Use an
8" Round Duct. It Can
Transition to a
3-1/4" x 12" Duct.
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 feet.
Flexible ducting:
If flexible metal ducting is used,
all the equivalent feet values
in the table should be doubled.
The flexible metal duct should
be straight and smooth and
extended as much as possible.
DO NOT use flexible plastic
ducting.
NOTE:
Any home ventilation
system, such as a ventilation hood,
may interrupt the proper flow of
combustion air and exhaust
required by fireplaces, gas
furnaces, gas water heaters and
other naturally vented systems.
To minimize the chance of
interruption of such naturally
vented systems, follow the
heating equipment manufacturer’s
guidelines and safety standards
such as those published by NFPA
and ASHRAE.
Total
Equivalent
Quantity Equivalent
Duct Piece
Dimensions
Length*
Used
Length
Round,
1 ft.
straight
(per foot
length)
3-1/4" x 12"
1 ft.
straight
(per foot
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° flat 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
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.
Installation Preparation
Total Duct Run
*Actual length of straight duct plus duct fitting
equivalent. Equivalent length of duct pieces are
based on actual tests conducted by GE Evaluation
Engineering and reflect requirements for good
venting performance with any ventilation hood.
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