Calculating The Duct Length - Miele T 5206 Operating And Installation Instructions

Installation - Venting

Calculating the Duct Length

The shortest passage for the expelled
air is preferable, to ensure the tumble
dryer functions most efficiently. Ex-
pelled air is slowed down in the vent
duct due to friction against the inner
walls of the duct, therefore the shorter
the duct and the smoother the inner
walls, the less friction occurs.
An elbow or bend creates more friction
than a straight duct. An additional duct
length factor should therefore be calcu-
lated for each elbow or bend (see Table
1). This factor expresses the resistance
of the bend in terms of a straight length
of duct.
The additional length factor is then
added to the actual duct length to give
the effective total duct length.
A larger duct diameter also helps to re-
duce friction. The duct diameter should
therefore increase with increasing duct
length.
Table I
Type of bend
Flexible ducting (heat resistant)
Plain ducting (heat resistant)
Plastic ducting (heat resistant)
Elbow
Concertina bend
Wall vent with grille or window vent kit
Wall vent kit with flap or window vent kit
Exhaust connection to the left
28
To calculate the effective duct length:
^ Measure the actual duct length.
^ Establish the number of elbows or
bends necessary, noting the type of
bend, angle and radius involved (see
Table I).
^ Add the additional length factor as
specified in Table I to the actual duct
length to give the effective duct
length.
^ The appropriate duct length can then
be taken from Table II.
Note
Drying times and energy consumption
remain unaltered for Ø100 mm ducting
up to a total length of 15 metres. Lon-
ger ducting may lead to slight in-
creases in drying times and energy
consumption, but does not impair the
function of the machine, if the neces-
sary duct diameter is adhered to (see
Table II).
Angle Radius R
in mm
90° 100 to 400
45° 100 to 400
90° 100
90° 200
90° 200
Additional duct
length in metres
0.5
0.3
0.35
0.25
2.3
0.7
3.6
1.25
1.0