Calculating The Total Ducting Length - Miele PDR 507 EL Operating And Installation Instructions

Calculating the total ducting
length
The entire ducting system (including
bends and components) generates air
resistance that pushes against the
exhaust air. The relative pipe lengths
and total ducting length have to be
calculated for this reason:
– The  relative pipe length (table I)
indicates how much greater the air
resistance of a bend is, for example,
compared to 1 metre of a straight
plastic pipe.
– Adding all of these relative pipe
lengths together gives the  total
ducting length. This is not the actual
length but a calculated figure. The
total ducting length (table II)
represents the air resistance of the
entire exhaust air system.
Because a larger  pipe diameter (ta-
ble II) reduces the air resistance, a
longer total ducting length requires a
greater pipe diameter.
Procedure
 Measure the length needed for the
straight sections of ducting. Multiply
the length by the corresponding
relative pipe length from table I.
 Calculate the number of bends and
elbows needed. Use table I to help
you add together their relative pipe
lengths.
 Calculate the total length of the
ducting: Add up all of the relative
pipe lengths calculated under 
and .
Installation of the ducting
 Refer to table II for the pipe diameter
needed for the total ducting length.
Table I
Components
Exhaust air hose
(highly flexible)
1 m, installed straight
45° bend (radius of bend = 0.25 m)
90° bend (radius of bend = 0.25 m)
Exhaust air hose (flexible or
flexible aluminium) /
plastic pipe
1 m, installed straight/straight pipe
45° bend (radius of bend = 0.25 m)
90° bend (radius of bend = 0.25 m)
Wall pipe or window connection
with inserted grate
with non-return flap (swinging flap)
Non-return flap for integration
into the ducting
(see "Shared exhaust air duct")
Flat ducting (for stacked
installation)
Table II
 Total ducting
length
maximum 20 m
maximum 40 m
maximum 80 m
 Relative
pipe
length
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
 Pipe diameter
100 mm
125 mm
150 mm
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