Problem with Redundancy Modicon Quantum PLC System


Thread Starter

Ulianov Gil

I have a Modicon Quantum PLC 434 in a Redundancy System with the Hot standby Module CHS, but I have a problem when the PLC A is working, after 3 or 5 days It switch to the PLC B without reason. I don't know why!

Can anyone help me?
Have you contacted Schneider Support? Could be any number of things. A repeatable switch-over after a 3-5 day period indicates an issue beyond hardware or software. The support people will want to know about rev levels of hardware and software and the PLC hardware configurations.
I had a similar problem a long time ago. My memory is kinda fuzzy, but i seem to remember that i had a dip switch (or jumper, or key) set wrong. I think we figured outt hat the CHS was just getting confused and swapping processors or somethign like that. At any rate, I had setup problems, and I needed tech support to figure it out.

Of course, i broke down and called them after replacing everything in the cabinet. Even if you have to pay for tech support, calling them now is gunna be cheaper than replacing everything and THEN calling them.

For Concept software:
1. Connect with CPU.
2. Open menu Online\Memory statisctics.
3. See PLC Scan Time.
4. Open Menu Configure\Specials
5. See Watchdog Timeout.
6. Set Watchdog Timeout > PLC Scan Time + 50..100ms.
7. Open Menu Configure\I/O map.
8. Set Holdup > Watchdog Timeout +50...100ms.

or (if all OK):

1. Download in CPU, CRP and CHS new firmware (see
Try to update your firmwares in CPUs, in CRPs and in CHS Modules.

If you have 140 CPU 43412, then update to 1.18e. If you have 140 CPU 43412A, then update to 1.26e.
140 CHS 110 00 must be on fw version 1.04
140 CRP 93x xx must be on fw version 1.15
Ask your local Schneider Office for this updates.