Siemens S5-135U/155U System Manual page 48

Installation Guidelines
Load Power
Supply
Grounding
Caution
!
For ungrounded power supplies, you must provide insulation monitoring if⁄
3-22
For 24 V DC load circuits, you require a load power supply unit with
safety separation. If an AC plug is used as the isolating device, the socket
must be in the vicinity of the central controller and easily accessible
(VDE 0805, 1.7.2).
Unregulated load power supply units require a reservoir capacitor
(rated at 200 mF per 1 A load current). Connect the capacitor in parallel
with the output terminals of the load power supply.
According to DIN VDE 0113, Part 1, control systems with more than five
items of electromagnetic apparatus require isolation by a transformer;
according to DIN VDE 0100, Part 725, it is recommended
Load power supplies should be grounded if possible
detachable connection to the protective conductor at the load power
supply unit (terminal L- or M) or on the secondary side of the isolating
transformer.
hazardous system states can be caused by double faults;
there is no safety separation;
circuits are operated with voltages of more than 120 V DC;
circuits are operated with voltages of more than 50 V AC.
.
. Provide a
System Manual
C79000-G8576-C199-06