Wiring and Fitting Modules
4.3 Wiring fail-safe modules
All voltage sources, for example, internal 24 VDC load voltage supplies, external 24 VDC
load voltage supplies and 5 V DC bus voltage, must be electrically connected externally.
This prevents potential differences from causing voltage additions at the individual voltage
sources which would cause the fault voltage U
Ensure that line cross-sections are sufficient for electrical connection in accordance with
the ET 200S configuration guidelines (see
Power supply Requirements for Compliance with NAMUR Recommendations
Always use power packs or power supplies (230 VAC --> 24 VDC) with a power failure ride-
through of at least 20 ms to ensure compliance with NAMUR recommendation NE 21,
IEC 61131-2 and EN 298. The latest up-to-date information on PS components is available
on the Internet (https://mall.ad.siemens.com).
These requirements also apply, of course, to power packs and power supplies which are not
manufactured to ET 200S or S7-300/-400 configuration standards.
Specifications for Nominal Line Voltages, Isolation Tests, Protection Class, and Type of
Protection (Page 60)
Wiring fail-safe modules
Same Wiring Procedure as for ET 200S
Fail-safe power modules, electronic modules and terminal modules are part of the ET 200S
range of modules. They are wired using the same procedure as for all standard modules in
an ET 200S.
Refer to the
on wiring and fitting the modules and IM 151.
When assigning signals of the F-DI module, remember that signals should only be routed
within a cable or sheathed cable if:
• A short-circuit in the signals does not conceal a serious safety risk
• Signals are supplied by different sensor supplies of this F-DI module
ET 200S Distributed I/O System
to be exceeded.
ET 200S distributed I/O system
operating instructions for detailed information
ET 200S Distributed I/O System - Fail-Safe Modules
Installation and Operating Manual, 08/2008, A5E00103686-07