5
General information
NOTE
: If you need to install ducts, note that the total
duct length of 3 ¼˝ x 10˝ rectangular or 6˝ diameter
round duct should not exceed 140 equivalent feet.
Outside ventilation requires a HOOD EXHAUST DUCT.
Read the following carefully.
NOTE
: It is important that venting be installed using
the most direct route and with as few elbows as
possible. This ensures clear venting of exhaust and
helps prevent blockages.
Also, make sure dampers
swing freely and nothing is blocking the ducts.
Exhaust connection:
The hood exhaust has been designed to mate with a
standard 3 ¼˝ x 10˝ rectangular duct.
If a round duct is required, a rectangular-to-round
transition adaptor must be used.
Do not use less
than a 6˝ diameter duct.
Maximum duct length:
For satisfactory air movement, the total duct length of
3 ¼˝ x 10˝ rectangular or 6˝ diameter round duct should
not exceed 140 equivalent feet.
Elbows, transitions, wall and roof
caps, etc.
present additional resistance to airflow
and are equivalent to a section of straight duct which is
longer than their actual physical size. When calculating
the total duct length, add the equivalent lengths of all
transitions and adaptors plus the length of all straight
duct sections. The chart below shows you how to
calculate total equivalent ductwork length using the
equivalent length in feet of some typical ducts.
DUCT PIECES
EQUIVALENT
LENGTH
x
NUMBER
USED
=
EQUIVALENT
LENGTH
Rectangular-to-Round
Transition Adaptor*
5 ft.
x
( )
=
ft.
Wall Cap
40 ft.
x
( )
=
ft.
90 ° Elbow
10 ft.
x
( )
=
ft.
45 ° Elbow
5 ft.
x
( )
=
ft.
90 ° Elbow
25 ft.
x
( )
=
ft.
45 ° Elbow
5 ft.
x
( )
=
ft.
Roof Cap
24 ft.
x
( )
=
ft.
Straight Duct 6˝ Round or 3 ¼˝
x 10˝ Rectangular
1 ft.
x
( )
=
ft.
Total Ductwork =
ft.
*
IMPORTANT
: If a rectangular-to-round
transition adaptor is used, the bottom
corners of the damper will have to be cut to
fit, using tin snips, to allow free movement
of the damper.
Equivalent lengths of duct pieces
are based on actual tests and reflect
the requirements for good venting
performance with any vent hood.
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