Calculating the effective duct
length:
Friction against the inner walls of the
ducting will slow down the expelled air
as it passes through. An elbow, 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
additional duct
length factor
. The additional length
factors are calculated by comparing
the friction created by, for example, an
elbow to that created by 1 metre of
straight plastic piping (Table I).
The additional duct length factor for
each item needs to be added together
to ascertain the
effective duct length
required.
A larger
internal duct diameter
also
helps reduce friction. If the effective
duct length is
more than 20 m
the
duct diameter should be increased
(Table II).
1. To calculate the effective duct
length required:
^
First measure the distance which will
require straight ducting. Multiply this
amount by the corresponding
additional duct length factor in
Table I
.
^
Establish the number of angles,
bends etc. necessary and add their
additional duct length factors
together with the help of
Table I
.
^
Add all the additional duct length
factors together to get the effective
duct length.
2. Internal duct diameter
^
Refer to
Table II
for the appropriate
duct diameter required.
Table I
Additional
duct length
factor
Flexible ducting*
–
1 m laid straight
–
45° angle
(Bend radius = 0.25 m)
–
90° angle
(Bend radius = 0.25 m)
1.8 m
1.5 m
2.5 m
Flexible aluminium ducting* / plastic
piping
–
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)
1.0 m
0.6 m
0.8 m
Wall vent kit* or window vent kit*
–
with louvred grille
–
with non-return flap (hinged flap)
3.8 m
1.5 m
Non-return flap* to be integrated into
the vent ducting
14.3 m
Flat ducting (for washer dryer
stack)*
11.0 m
Venting connection to the left/right
1.0 m
* optional accessory from Miele
Table II
Maximum effective
duct length allowable
Internal duct
diameter
required
10 m
with Ring adapter
20 m
without Ring adapter
40 m
without Ring adapter
100 m
without Ring adapter
100 mm
100 mm
125 mm
150 mm
Installation - venting
30
Summary of Contents for T 4123
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