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Friction against the inner walls of the
vent duct will slow down the expelled
air as it passes through the duct. An el-
bow, bend, non-return flap or wall vent
creates more friction than a straight
duct. The friction created by each of
these is expressed as an
. The additional length
factors are calculated by comparing
the friction created by, for example, an
elbow to that created by 1 meter of
straight plastic piping (Table I).
The additional duct length factor for
each item needs to be added together
to ascertain the
which will be needed for the venting
system.
A larger
helps reduce friction. If the effective
duct length is
duct diameter should be increased (Ta-
ble II).
^ First measure the distance which will
require straight ducting. Multiply this
amount by the corresponding addi-
tional duct length factor in
^ Establish the number of angles,
bends etc. necessary and add their
additional duct length factors to-
gether with the help of
^ Add all the additional duct length fac-
tors together to give the effective
duct length.
^ Refer to
duct diameter for the effective duct
length.
–
1 m laid straight
–
45° angle
(Bend radius = 0.25 m)
–
90° angle
(Bend radius = 0.25 m)
–
1 m laid straight / or 1 m
straight pipe
–
45° angle / elbow
(Bend radius = 0.25 m)
–
90° angle / elbow
(Bend radius = 0.25 m)
also
–
with louvred grille
–
with non-return flap
the
(hinged flap)
* These can be obtained from the Miele Spare
Parts department or from builders' merchants.
.
.
for the appropriate
20 m
40 m
100 m
1.8 m
1.5 m
2.5 m
1.0 m
0.6 m
0.8 m
3.8 m
1.5 m
14.3 m
11.0 m
1.0 m
100 mm
125 mm
150 mm
37
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