Switching between RUN and REM while live

[dbmcbb]

Can someone tell me if it is okay to switch from RUN to REM while a piece of equipment is being controlled by the PLC, or do I need to shut the machine down first?

The PLC in question is a ControlLogix.

Thank you in advance from a PLC novice!

 

[DGillen]

As far as I know, it is safe to switch a ControlLogix PLC from RUN to REM or back again without stopping the PLC. I tried it on a SLC in my shop and it can be changed while running.

Just be careful not to switch it to PROG mode by accident. That will stop the PLC.
This usually upsets most production leaders and plant managers.

And if possible, remove the key and store it in a safe place.

 

[Ken Roach]

98% of the time you can switch from RUN to REM RUN mode with no problem.

1% of the time, you reach too far into the cabinet and stumble a little and end up switching into PROG mode accidentally. Ask me how I know.

1% of the time, the user program includes code that reads the keyswitch position and disables part of the machine functionality if the key is not in hard RUN mode. This is common with systems that must not be modified during runtime, like burner controls.

 

[dbmcbb]

Thank you for the quick and detailed answers. I did switch from RUN to REM without an incident! My heart is still a little stressed over it, but now this will stick with me for life and I won't be so fearful next time!

 

[Ron Beaufort]

and I won't be so fearful next time!

PLCs are sort of like motorcycles ... when you reach the point that you're not afraid of them, then it's time to trade it in for a car ...