12
Ductwork
Component Cooktop System
Total
Equivalent Quantity
Equivalent
Duct Piece
Dimensions
Length*
Used
Length
1 ft.
6" round,
(per foot
straight
length)
1 ft.
3-1⁄4" x 10"
(per foot
straight
length)
6"
90
°
elbow
15 ft.
6"
45
°
elbow
9 ft.
3-1⁄4" x 10"
90
°
elbow
15 ft.
3-1⁄4" x 10"
45
°
elbow
9 ft.
3-1⁄4" x 10"
90
°
flat elbow
20 ft.
6" round
to 3-1⁄4" x 10"
transition
1 ft.
3-1⁄ 4" x 10"
to 6" round
transition
5 ft.
6" round to
3-1⁄ 4" x 10"
transition
90
°
elbow
5 ft.
3-1⁄ 4" x 10" to 6"
round transition
90
°
elbow
15 ft.
6" round
wall cap
with damper
30 ft.
3-1⁄ 4" x 10"
wall cap
with damper
30 ft.
6" round
roof cap
26 ft.
6" round
roof vent
24 ft.
Total Duct Run
Use copies of this
form to compute
maximum
permissable lengths
for duct runs to
outdoors.
ZEW166 Downdraft Grill
Component maximum
equivalent length is
100 feet.
ZEW176 Downdraft Vent
Component maximum
equivalent length is
150 feet
Note:
Do not exceed maximum
permissable equivalent lengths!
Flexible ducting:
If flexible metal
ducting is used, all
the equivalent length
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.
Duct
fittings
* Actual length of straight duct plus duct fitting
equivalent. Equivalent length of duct pieces are based
on actual tests conducted by GE Evaluation Engineer-
ing and reflect requirements for good venting
performance with any downdraft cooktop.
CAUTION:
Any home ventilation system, such
as a cooktop with a downdraft
exhaust mechanism, 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.
