Wiring and Fitting Modules   
4.3 Wiring fail-safe modules 
  ET 200S Distributed I/O System - Fail-Safe Modules 
34  Installation and Operating Manual, 08/2008, A5E00103686-07 
WARNING 
 
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
m
 to be exceeded.  
Ensure that line cross-sections are sufficient for electrical connection in accordance with 
the ET 200S configuration guidelines (see 
ET 200S distributed I/O system 
operating 
instructions). 
 
Power supply Requirements for Compliance with NAMUR Recommendations 
 
 
Note 
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. 
 
See also 
Specifications for Nominal Line Voltages, Isolation Tests, Protection Class, and Type of 
Protection (Page 
60) 
4.3  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 
ET 200S Distributed I/O System
 operating instructions for detailed information 
on wiring and fitting the modules and IM 151. 
 
WARNING 
 
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