Siemens SIMATIC S7-400H System Manual page 274

Failure and replacement of components during operation
16.2 Failure and replacement of components during operation
Procedure
The double error described results in loss of redundancy. In this event proceed as follows:
Step
1
2
3
4
274
What has to be done?
Switch off one subsystem.
Replace the faulty components.
Turn the subsystem back on.
Start the CPU (for example Start from
programming device or STOP - RUN).
How does the system react?
–
–
LEDs IFM1F and IFMF2F go off. The

LED MSTR of the switched on
subsystem goes out.
The CPU performs an automatic LINK-

UP and UPDATE.
The CPU changes to RUN (redundant

system mode) and operates as reserve
CPU.
System Manual, 03/2012, A5E00267695-11
S7-400H