Siemens SIMATIC ET 200M Manual page 155

Maintenance
In the Case of Redundancy
Note
Only replace the IM 153-2/-2 FO in a de-energized state!
If you carry out a replacement in an energized state, the specified switchover
times cannot be guaranteed and the I/O modules could fail for a certain time and
output "0".
If you replace the IM 153-2/-2 FO in a redundant configuration, the following
applies:
"ACT" LED is on:
The IM 153-2/-2 FO is the active one of the
two IM 153-2/-2 FO modules.
Removing a Module
To remove the module, proceed as follows:
1. In the case of redundancy: The IM 153-2/-2 FO to be replaced must be
de-energized! Switch off the associated power supply module or disconnect it
from the IM 153-2/-2 FO.
Warning
!
If in redundancy mode the two IM 153-2 modules are connected to a power supply
module, a short circuit could occur at the non-insulated (loose) cable ends if the
24 V supply is disconnected from one of the IM 153-2.
If the power supply is short-circuited in this way, the second IM 153-2 and
therefore your ET 200M fail completely.
The greatest care must therefore be taken when disconnecting the supply voltage
and the two cable ends must be insulated until they are connected to the new
IM 153-2.
No redundancy: Put the on/off switch of the power supply module into the 0
position ( : output voltage 0 V).
2. Remove the bus connector or fiber-optic cable.
In the case of fiber-optic cables: Flip open the grip of the plug-in adapter and
remove it from the IM 153-2 FO.
7-6
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"ACT" LED is off:
The IM 153-2/-2 FO is the passive one of
the two IM 153-2/-2 FO modules.
You can replace these IM 153-2/-2 FO
modules without the need for switchover
operations in the ET 200M.
Distributed I/O Device ET 200M
EWA-4NEB780600602-06