GE JVM1490 Installation Instructions Manual page 5

Installation instructions
NOTE: If you need to install ducts, note that the total
duct length of 3¼" x 10" rectangular or 6" diameter
round duct should not exceed 140 equivalent feet.
Outside ventilation requires a HOOD EXHAUST DUCT.
Read the fbllowing careflflly:
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 blocMng the ducts.
Exhaust connection:
The hood exhaust has been designed to mate with
a standard 3¼" 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 safisfhctory air movement, the total duct length of
3¼"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 equNa/ent lengths of all transitions and
adaptors plus the length of all straight duct sections.
The chart below shows you how to calculate total
equiwdent ducta, vork length using the approximate feet
of equivalent length of some typical ducts.
DUCT PIECES
&
Rectangular-to-Round
TransitionAdaptoP
Wall Cap
90° Elbow
EQUIVALENT
LENGTH
5 Ft.
40 Ft.
10 Ft.
X
NUMBER
USED
( )
( )
( )
EQUIVALENT
LENGTH
Ft.
Ft.
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 1 Ft. x ( ) = Ft.
3X" x 10" Rectangular
Total Ductwork = Ft.
* IMPORTANT: If a rectangula>to-round transition
adaptor is used, the bottom corners of the damper
will ha_e to be cut to fit, using the tin snips, in
order to allow ti'ee movement of the damper.
Equivalent lengths of duct pieces are based on actual tests and
reflect requirements for good velltillg performance x_dth any
Vellt hood.
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