PLC5 Trouble

No way to know without knowing your wiring and programming. But I would not waste a lot of time with coils, contactor aux contacts and things like that. TYPICALLY if you have a hardwired interface, you would have the N.O. aux contact of the OVERLOAD relay wired to a PLC input. If that contact is welded closed, that would explain it. But also if the wires for that circuit are improperly run and are picking up an induced voltage, that may be triggerring your input too. Could be a lot of other things too.

I would start by identifying the PLC input that is associated with determining that the motor starter detects an overload. Lift the wire off AT the PLC input and make sure the input status changes. If it doesn't, then it's likely a bad card or something else in the PLC. If the status changes when you lift the wire, the problem is in the circuit. Put it back on and lift the wire AT the overload relay. If the status changes, its the relay. If it doesn't, then you are getting voltage onto the input wire from somewhere else.

If there is no wire coming from the OLR N.O. aux contact, then your PLC programming is using some other method of detecting an OL condition. Sometimes (bad idea), a programmer will use logic such as "If a Start command was given AND no feedback was received, THEN it must mean it is tripped on Overload". It's not a good logic plan, but some people are cheap and don't want to have the OL aux. contact wired back to the PLC, I see it all the time. the problem is, it is not truly indicative of an actual overload trip, could be a LOT of other issues.

Good luck.

GA, but the system is plugged right now and not accepting votes.

BTW, congratulations on crossing the 300 mark, and thanks for many informative postings!

Sorry for not getting back until now. We'll it was the remote I/o card on the main rs5000 rack. I do believe we gotter wooped. Thanks for the help

1) What is the rating of input card, 24VDC or 110VAC?

2) Are the motor starter and remote I/O card wired in same cabinet?

3) What is the normal state of aux contact of overload, normally CLOSED (input remains ON).

Such kind of "momentarily" problems take time to resolve.

Its just a card that's a little old 3 or 4the yrs old. We got a new one and so far we've had no problems