PLC5 DVNA Alarm Latching on disabled PID Loops

Hayden · Dec 5, 2011

I have a PLC5 tripping a DVNA (Deviation High Alarm) every few months on PID loops that are not enabled.

Both alarms that are tripping (PD12:20.DVNA, PD12:26.DVNA) are not enabled loops and the alarm stays latched, which requires us to connect with a PC and toggle the alarm.

Has anyone seen this before or have a work around?

Mickey · Dec 5, 2011

First how are you disabling the loop?

And why not just disable the alarm? You would have to be using that bit some where in your logic to cause a problem or monitoring it with a HMI/SCADA system.

Hayden · Dec 5, 2011

PD12:20.EN is set to 0

How do I disable the alarms?
They are not being written to from any HMI or SCADA as far as I can see and I am familiar with the system. The only reference in the program was a XIC tag.

Thanks for your help

Mickey · Dec 5, 2011

Hayden said:
PD12:20.EN is set to 0

How do I disable the alarms?
They are not being written to from any HMI or SCADA as far as I can see and I am familiar with the system. The only reference in the program was a XIC tag.

Thanks for your help

Post your .RSP file and someone will help you look. Zip the file first then post.

Hayden · Dec 5, 2011

Unfortunately I cant do that due to confidentiality restrictions.

I have looked but cannot seem to find a comprehensive guide to the PID tags for PLC5. If someone could direct me to that doc I'm sure I could find a way to disable the alarm permanently.

Ron Beaufort · Dec 5, 2011

the PLC-5 Instruction Set Reference Manual is about as comprehensive as it gets ...

http://literature.rockwellautomation.com/idc/groups/literature/documents/rm/1785-rm001_-en-p.pdf

see Chapter 14 for PID ...

PLC5 DVNA Alarm Latching on disabled PID Loops

Hayden

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