3. HOOD EXHAUST
(
CONT
’
D
)
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, ensure damper swings freely and nothing is
blocking the ducts.
E
XHAUST
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 adapter must be used.
Do not use less than a 6”
diameter duct.
M
AXIMUM
DUCT
LENGTH
:
For satisfactory air movement, the total duct length of 3¼” x 10” rectangular or 6” diameter round duct should not
exceed 140 equivalent feet.
E
LBOWS
,
TRANSITIONS
,
WALL
AND
ROOF
CAPS
,
ETC
.
These duct pieces present additional resistance to airfl ow 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 adapters plus the length of all straight duct sections. The chart below shows you how to calculate
total equivalent ductwork length using the approximate feet of equivalent length of some typical ducts.
*If a rectangular-to-round transition adapter is used, the bottom corners of the damper will have to
be cut to fi t, using a tin snips, in order to allow free movement of the damper.
Equivalent lengths of duct pieces are based on actual tests and refl ect requirements for good venting performance
with any vent hood.
DUCT PIECES
EQUIVALENT
LENGTH
X
NUMBER
USED
=
EQUIVALENT
LENGTH
Rectangular-to-round
transition adapter*
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 3¼” x 10”
rectangular or 6” round
1 ft.
x
( )
=
ft.
TOTAL
DUCTWORK
=
ft.
MR0004
MR0005
6
