Distances And Cable Lengths - Siemens RXB Series Basic Documentation

Bus cable: KNX specified
Network with DPSU
Network with PSU
Notes
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Siemens
Building Technologies
2.3.1

Distances and cable lengths

The details of distances and cable lengths in a network are designed for bus cables
specified by KNX.
In a KNX network with a "decentral bus power supply unit, DPSU" (see Section
2.2.1), the distances between devices depend on the number of devices with a
DPSU.
Number of
From device
devices with
with DPSU
DPSU
to bus device
1
2
3 to 8
There is no minimum distance between devices with a DPSU.
1)
Bus device without bus power supply unit
In a KNX network with "central bus power, PSU" (see Section 2.2.2), note the
following information on distances:
Distance between two power supply units, PSU
Distance between bus device and nearest PSU
Distance between bus devices
Total length of all cables of one line
At least one power supply unit, PSU, is required for each line, and the maximum
per line is two.
The power supply unit should be installed as close to the middle of a line as
possible so that the maximum line length is possible.
The distance between a bus device and the nearest power supply unit must not
exceed 350 meters. Thus:
Even if the power consumption of the bus devices does not demand it, two
power supply units may be required, depending on the length of a line, or a
network with several lines and power supply units must be created.
KNX bus communications
Engineering notes
Maximum distance
From bus device
to bus device
350 m 350 m
350 m 700 m
350 m 700 m
Total length of all
cables on one line
max. 350 m
max. 700 m
max. 1000 m
Min. 200 m
Max. 350 m
Max. 700 m
Max.1000 m
For internal use only
CE1P3127en
2013-04-08