Ductwork
Component Cooking Surfaces
4
Step Installing
theDuctwork(continued)
Duct
fittings
Use copies of this form to
compute maximum
permissible lengths for
duct runs to outdoors.
Note: Donot exceed maximum
permissible equivalent lengths!
Flexible dueting
Ifflexible 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.
Component Cooktop System
100’ maximum equivalent
length
CAUTION:
Any home ventilation system, such
as acooktop with adowndraft
exhaust mechanism, may interrupt
the proper flow of combustion air
and exhaust required byfireplaces,
gas furnaces, gas water heaters
and other naturally vented
systems. Tominimize 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
m
1ft.
6“ round, (per foot
straight length)
)
1ft.
3-1/4” x1o“ (per foot
v / straight length)
Q
6“
90° elbow 15 ft.
@
~,1
45° elbow 9ft.
@
3-1/4” x1o“
90° elbow 15 ft.
Q
3-1/4” xlo”
45° elbow 9ft.
Ga 3-1/4” x1o“
90° flat elbow 20 ft.
%6“round
to .3-1/4”x1o“
transition 1ft.
4
3-1/4” xlo”
to 6“ round
transition 5ft.
%6“ round to
%1/4” xlo”
transition
90° elbow 5ft.
Q
3-1/4” X10” to 6“
round transition
90° elbow 15 ft.
@
6“round
wall cap
with damper 30 ft.
m
3-1/4” x1o“
wall cap
with damper 30 ft.
@
6“round
roof cap 26 ft.
@
6“round
roof vent 24 ft.
Llagrarn
481
Total Duct Run_
●Actuallength of straight duct plus duct fitting
equivalent. Equivalent Length of duct pieces are based
on actual tests conducted by GEEvaluation Engineer-
ing and reflect requirements for good venting
performance with any downdraft cooktop.
48