Whether Single CI840 with TU847 works or not
If we remove one CI840 from TU847 can the system runs with single CI840?
Yes it will work and system will be running.
CI840 supports redundancy. Just make sure that both Profibus is healthy (Profibus A & Profibus B connectors). If both are healthy, you can remove any CI840 and System Will be running and it is supposed to run.