Over The Range Convection Microwave Oven / Installation Manual
10 / 63 EN
4
External exhaust
4.1.4 Maximum duct length
For satisfactory air movement, the total duct
length of 3
1⁄4
” x 10” (8.2 x 25.4 cm) rectangular or
6” (15.2 cm) diameter round duct should not ex-
ceed 120 equivalent feet (36.5 m).
4.1.5 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 cal-
culating the total duct length, add the equivalent
lengths of all transitions and adaptors plus the
length of all straight duct sections. The chart be-
low shows you how to calculate total equivalent
ductwork length using the approximate feet of
equivalent length of some typical ducts.
Duct pieces
Equivalent
Length
x
Number
used
=
Equivalent
Length
Rectangular-to-Round
Transition Adaptor*
5 Ft. (1.5 m)
x
( )
= Ft. or m
Wall Cap
40 Ft. (12.2 m) x
( )
= Ft. or m
90° Elbow
10 Ft. (3 m)
x
( )
= Ft. or m
45° Elbow
45° Elbow
x
( )
= Ft. or m
90° Elbow
25 Ft. (7.6 m)
x
( )
= Ft. or m
