Commissioning Notes - Siemens Desigo TRA Engineering, Mounting And Installation Manual

Notes
Power supply AC 24 V
PXC3 only
Permissible load [VA]
Wiring KNX bus
Polarity
Operating voltage
Bus power supply
Siemens
Building Technologies
At least one supply (internal or external) is required for each line, and max. two
supplies (external) are allowed per line.
Install the power supply unit as close to the network center as possible to
achieve maximum line size.
The distance between the device and the next neighboring PSU may not exceed
350 m / 1100 ft. As a result:
Even if the power demand from the devices does not require it, two power
units must be used depending on the line length.
The PXC3 room automation station also includes an AC24V / 2 A / 48 VA output for
devices with increased power consumption that is supplied via AC 24V rather than
via the KNX bus.
Voltage drop off between the room automation station and devices with KNX is
maximum -7 % (-1.7 V).
The table below provides permissible loads based on cable lengths and cable
cross sections.
AWG NO.
Cable cross
section (diameter)
AWG20
2
0.5 mm (0.8mm)
AWG18
2
0.8 mm (1.0mm)
AWG16
2
1.3 mm (1.3 mm)
AWG14
2
2.1 mm (1.6mm)

12.4 Commissioning notes

Observer the following commissioning aspects to commission a KNX network as
intended.
Check the bus wiring prior to commissioning, and make sure that the bus line
polarity is not interchanged (KNX terminals + and –).
Check the operating voltage wiring to make sure that the devices are connected to
AC 24 V or AC 230 V (as per the technical device information). Apply operating
voltage only after this check.
After switching on operating voltage, you must check whether bus power from the
room automation station or the PSU is available.
Desigo TRA Engineering, mounting and installation
KNX PL-Link room bus
Cable length for AC 24 V
10 m 20 m
33 ft 65 ft 165 ft
48 VA 30 VA 12 VA
48 VA 48 VA 20 VA
48 VA 48 VA 32 VA
48 VA 48 VA 48 VA
50 m 100 m 200 m
330 ft 650 ft
6 VA
10 VA
16 VA
24 VA 12 VA
CM111043en_09
3 VA
5 VA
8 VA
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2016-02-22