Miele T 7634 Calculating total duct length, Arrangement Left or right dryer vent opening

Installing the dryer vent

Calculating total duct length

Each of bends and differing components of the dryer's venting creates its own frictional resistance to the flow of the exhaust air. This frictional resistance is expressed in a comparative duct length. The comparative duct length indicates the length of a smooth straight pipe (of the same diameter), producing the same resistance to air flow as the original ducting component (Table I).

Adding together the comparative duct lengths of all components reveals the total duct length. The total duct length is a calculated value that compares how long a smooth straight venting pipe would have to be for the same air flow.

Since an internal pipe diameter strongly affects flow's resistance, a vent with a total duct length exceeding 20 m requires a larger diameter (Table II).

Procedure

1.Measure the distance requiring straight ducting. Multiply this value by the corresponding comparative pipe length from Table I.

2.Determine the number of bends and components required. Add their comparative lengths together using Table I.

3.Add together all the comparative lengths thus determined: Thus you obtain the total duct length.

4.From Table II, determine which internal duct diameter is required for the total duct length.

Table I

Components	Comparative duct length
Flexible ducting
– 1 m laid straight		1.8 m
– 45° bend		1.5 m
(Bend radius = 0.25 m)
– 90° bend		2.5 m
(Bend radius = 0.25 m)
Vent hose(flexible or Alu-Flex)
– 1 m laid straight or 1 m straight		1.0 m
pipe
– 45° bend		0.6 m
(Bend radius = 0.25 m)
– 90° bend		0.8 m
(Bend radius = 0.25 m)
Wall vent kit or window vent kit
– with grill insert		3.8 m
– with non-return flap (hinged flap)		1.5 m
Non-return flap* for integration		14.3 m
into the vent ducting
(see section "￿ Vent collector
duct")
Flat duct (for stacked		11.0 m
arrangement)
Left or right dryer vent opening		1.0 m
* Miele accessory available on order

Table II

Maximum permissible	Diameter required
total duct length
20 m	100 mm
40 m	125 mm
100 m	150 mm

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