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Siemens
Desigo TRA Engineering, mounting and installation
CM111043en_09
Building Technologies
Wiring of field devices (without bus)
2016-02-22
7
Wiring of field devices (without bus)
This section describes the wiring between the room automation station / the TX-I/O
module and the field devices.
7.1 Signal
wiring
The following applies in common for signal wiring of field devices such as
temperature sensors, window switches, presence detectors, dew point sensors or
electrical buttons, as well as DC 0...10 V devices:
Use stranded, 2 or multiple core round cables, without screen (standard off-the-
shelf installation cable).
Single wires or ribbon cables may not be used.
Signal wiring may be laid together with power lines (AC 230 V).
They must be isolated from the power lines per regulations. Isolation must meet
PELV requirements.
Signal wiring can
not be led in the same cable
as the power lines.
The length must not exceed the following values (measuring errors, EM
interference):
– PXC3... , RXM...
300 m / 1000 ft
– DXR2
80 m / 260 ft
Exceptions (hum injection) see page 35.
Min. 0.5 mm
2
/ AWG 24
All system neutral terminals of a device are interconnected.
TX-I/O:
The connection is
not
in the terminal base but in the plug-in module.
When this unit is unplugged there is no connection.
The system neutral of a
digital input
can be connected to any signal neutral
terminal of the device.
It is also permissible to combine the system neutral conductors of several digital
inputs in order to save wire.
TX-I/O:
However, system ground must be connected at least once per module.
With
analog inputs and outputs
, the measuring neutral must always be
connected to the terminal associated with that specific I/O point to avoid possible
measurement errors.
DC 0…10 V actuators with DC 0…10 V feedback:
System neutral of output and feedback may be in the same conductor due to the
small current of the AO 0-10V und AI 0-10V signals. However, output and
feedback must be on the same device and there is no DC 24 V supply current
admissible on the system neutral conductor.
Cable material
Cable laying
Cable length
Cable cross section
System neutral termi-
nals ( , M, GND, G0):
