GE JVM1490 Installation Instructions Manual page 5

Installation Instructions
NOTE: If you need to install ducts, note that the total
duct lengtb of 3¼" x 10" rectangular or 6" diameter
round duct should not exceed 140 equivalent feet.
Outside ventilation requires a HOOD EXHAUST DUCT.
Read tile following carefully.
NOTE: It is important tbat 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 witb
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 satisfhctory 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
lengtb, add tbe equivalent lengtbs of all transitions and
adaptors plus tbe length of all straight duct sections.
The chart below shows you how to calculate total
equivalent ductwork length using the approximate feet
of equivalent lengtb of some typical ducts.
EQUIVALENT NUMBER EQUIVALENT
DUCT PIECES LENGTH x USED = LENGTH
Rectangular_to-Round 5 Ft. x ( ) Ft.
TransitionAdaptor*
Wall Cap 40 Ft. x ( ) Ft.
(i)_ 9O°EIbow lOFt. x ( ) Ft.
(_ 45° Elbow 5 Ft. x ( ) Ft.
90° Elbow 25 Ft. x ( ) Ft.
45° Elbow 5 Ft. x ( ) Ft.
RoofCap 24 Ft. x ( ) Ft.
Straight Duct6" Roundor 1 Ft. x ( ) Ft.
3¼" x 10" Rectangular
Total Ductwork = Ft.
* IMPORTANT: if a iectangtflm_to-round transition Equiwflent lengths of duct pieces are based on actual tests and
adaptor is used, the bottom cornm_ of the damper reflect requirements for good venting performance with any
_'iU ha_e to be cut to fit, t_sing the tin snips, in _ent hood.
order to aUo_ fi'ee inovement of the damper.
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