Siemens S5-135U/155U appendix Load Power, Grounding

Installation Guidelines

Load Power

SupplyS 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).

SUnregulated load power supply units require a reservoir capacitor à (rated at 200 mF per 1 A load current). Connect the capacitor in parallel with the output terminals of the load power supply.

SAccording 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 Ä.

Grounding

SLoad power supplies should be grounded if possible Å. Provide a 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.

!	Caution
	For ungrounded power supplies, you must provide insulation monitoring if¤

Shazardous system states can be caused by double faults;

Sthere is no safety separation;

Scircuits are operated with voltages of more than 120 V DC;

Scircuits are operated with voltages of more than 50 V AC.

3-22	System Manual
	C79000-G8576-C199-06