Device-Specific Regulations - Siemens Desigo TRA Mounting And Installation Manual

Emergency intervention
of power components
. Field device
connection
Devices using different
power circuits
Interfaces for different
voltage circuits
PXC3...
supply AC 24 V
12 / 56
Siemens
Building Technologies
Peak loads occur when switching inductive loads that may cause faults to the
system. In addition, sparks may damage switching contacts. Power components
must include effective protection against disturbances to prevent such faults.
Inductivity (transformers, fuses, relays) are wired directly at the terminals using
transzorbs, MOVs (metalloxyd varistors) or RC elements. The breakdown voltage
of the transzorbs or MOVs must equate to the 1.7 to 2 times the applicable nominal
voltage.
Inductive DC consumers can also be suppressed using diodes or RC elements.
The transzorbs, MOVs, diodes or RC elements must be optimally matched to the
power components and mounted using short wiring.
3.2

Device-specific regulations

Devices must have the required insulation of the power circuits from each other to
be able to connect them directly without additional insulation.
Connections via interfaces increase the risk of distributing dangerous voltage
through the building. Ensure that the required insulation is available at all times and
installed per applicable regulations.
The supply terminals of the PXC3... (terminals 7 and 8) bare a max current of
10 A, otherwise the pins get too warm.
An external T10 A fuse is compulsory
Mounting and installation
Important information on safety
CM111043en_03
2013-02-23