ge plc pid loop not moving

[joeparrish]

First off let me say I am not very good with ge plc's.

We have a pid ISA loop that the cv never changes it is a max and stays at max.

Looking at the loop I see the pv move up and down and I can change the sp up or down on our screen.

However if I right click and go to tune the loop The pv shows going up and down but the sp is a different number than what is set and does not move.

Any suggestions would be great.

Thanks in advance

 

[Steve Bailey]

Has it ever worked properly or are you trying to set it up for the first time?

 

[joeparrish]

Yes they said it has been working

 

[Steve Bailey]

The CV stuck at maximum could be the result of the function running for a long time at too high a SP resulting in a large integral component.

 

[labeledas]

can you post screen shots of both the ladder and the config page, not familiar with ge but sounds like it is getting it's setpoint from another location similar to ABs program mode. also are you sure it's enabled the enable bit should have a true condition in front of it

 

[Steve Bailey]

Has anyone made any changes at all recently? It could be something else writing to the SP and overwriting what shows on your HMI.
Also, is the PID function enabled by logic true at the upper LH node on the function block? And logic false at the "MAN" node?

 

[labeledas]

I would also check to see if the SP limits have been changed.