Can't acknowlege system alarm. And alarm remains active.
In 800xA 5.1, I have two "System Condition Event" in alarm list that I can't acknowlege. The alarm wont go back to RTN either. Event details says Quality: Bad, Comm Failure.
First alarm is status from CPU, saying like "Warning on primary unit, Error on backup Battery Low, Redundant mode enable" and so on. But in Control builder everything is fine after resetting all faults. Then we same problem from one Profibus master, from about the same time.
If the status is updated (like removing controller cable/switching primary unit) the alarm gets a new time stamp on Active Time in alarm list, but after a few seconds the Active time jumps back to the old time stamp. Same if I delete the alarm, when I generate a new alarm it first appears like normal, but after a few seconds it gets overwritten with the old timestamp and old status description. And still cant acknowlege.
I think this happened when we did a test and removed battery and disconnected power to both primary and backup CPU (to test cold retain function).
We also had problem with one Process Condition Event/alarm with about samt time stamp, but after deleting that one it now works like normal. But not these two System alarms.
How can I fix this problem?
The HMI can neither delete nor force the alarm out of the OPC AE server. The PLC need to send RTN to OPC AE server to relay it to the HMI.
Delete is futile if alarm remain in OPC AE server - next refresh will bring it back.
A third party OPC AE client is a useful tool in circumstances like this.
1) Restart AC800 OPC server service in Windows
2) Try cold download to application owning the alarm
3) Reset controller and download again.