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Brief History:
First Trip: investigation showed we had a fuse blow when starting up the compressor on the stop button circuit,We had it changed out the stop push button and its contacts and also swapped the DAP 218 PLC cards for the fact that output 11 on that card also went to the stop button circuit. Once this was complete there was no issue starting the compressor.

Second Trip: two fuses for the STOP-push button located with the PLC panel and an E-stop fuse blew. Next we had the compressor shutdown and went thru all the instruments and the PLC panel checking for water bad wire spots or anything else that could cause a short and blow fuses. As we went thru all the connections we changed out all the covers with new covers. We also Ohmed out all the instrument wires and verified fuse sizes for the instruments. All wire checked good, we did find the feed fuses were smaller than our instrument fuses. We changed the instrument fuses to .5amp and the feed fuses to 5amp. We also discovered one conduit that was going into the PLC had lost it support which was putting strain on the fittings causing a small gap on the top of the PLC enclosure which had evidence of small drips of water coming in and landing on the power supply. We re-supported the conduit and tightened the fitting back down for a good seal on the PLC enclosure

Third trip due to a blown fuse going to the East ESD pull station. A grounded wire was discovered leaving the control Panel to the button, ie the neutral wire in the conduit going to the switch was shorted. The number 13 fuse is currently blown and will need to be re installed. Also an East Push button is damaged and not operational. Aside these, what other suggestions do you suggest need to be looked at for troubleshooting and repairs.

NOTE: Trips have occurred within a space of 3 weeks

Can someone advise on a Robust troubleshooting and repair plan for all possible electrical failure modes to address the trips and make the system more reliable?


How are you blowing all these fuses on PLC inputs? Only ways would be, they're shorting to ground or they're being vibrated to death.

Keith Cress
kcress - http://www.flaminsystems.com


Have to agree with Keith - blowing fuses repeatedly - in protection circuits not associated with compressor runup - usually means a ground issue somewhere that shouldn't be happening. I wouldn't rule out vibration entirely - but less likely if panels are mounted remotely from compressor skid.

Converting energy to motion for more than half a century

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