Chiller wiring disintegrating?

[ScienceRulez]

Came into work this morning to the tank at 83(f) and my APEX very unhappy about it.

After some troubleshooting I discovered one of the wires in my chiller that goes from the temperature controller to the condenser motor was shorting out. The cause? The insulation on the wire had totally disintegrated leaving nothing but bare wire. It caused a short and threw the breaker. I replaced the wire and reset the breaker and it started right up.

Why/how could this happen? The wires don't move around, it's a standard US 120 volt 3/4hp chiller for a 560 gallon tank. Is there a way to stop this from happening again? As for the chiller it was set up by my predecessor and I suspect he used cheap wire from Harbor Freight Tools, is this why? The original wire was also 12 gauge and I replaced it with what I had which is 10 gauge. I'm hoping that makes a difference too. But any theories here are welcome.

 

[Pittsburgh]

Insulation gets brittle with age, especially under constant temperature fluctuations. Also, the wire was connected to the motor, which likely caused constant vibration. Combined, I could see how this would happen.

 

[mcgyvr]

Type of insulation? PVC/polyethelyne/silicone?

Probably PVC.. Overheating (loose connection or local strand breakage or just sub par materials,etc...)

Fit Shappens and just another reason why routine preventative maintenance is performed all over the world..

 

[ScienceRulez]

It was cheap PVC stranded wiring that was used. It was just over 3 years old when I replaced the wire. The wire that was factory installed is silicone and there was no discernable damage except from the arcing with the short. I replaced that wire as well. The wire I used was solid wire with polyethethylene insulation. It was the best I had.

 

[mcgyvr]

I'd be a bit concerned using PE when "silicone" was used at the factory.. No one uses silicone if they don't absolutely need it but that may have just been for vibration mitigation more than heat issues..

But PE is better than PVC (aka usually a higher temp rating and Tg)
As I stated.. Just check it every once in a while as part of routine maintenance and all will be good..

Obviously matching or going larger on the wire gauge is a must.. I assume you did that..

I once took a technical call from a NASA employee who used 24 AWG wire for a 30 Amp circuit and wondered why it was hot.. He said it was only a 12V application and the wire said 300V.. I said it was current (resistive losses i2r) that causes the heat not the voltage and he hung up after saying "not in my book son"...

 

[ScienceRulez]

Ok, I will get some silicone insulated wire. The polyethylene was all I had at the time, the "original" wire was 12AWG stranded, and I replaced it with 10AWG solid. I'm thinking it should work for a couple weeks until I can get the silicone.

The main issue is that I have put in my notice and won't be here after October 1. Before me there was NO maintenance done at all and after I leave I doubt there will be any done either. I'm just burned out from this place after 5 years.

 

[mcgyvr]

The main issue is that I have put in my notice and won't be here after October 1. Before me there was NO maintenance done at all and after I leave I doubt there will be any done either. I'm just burned out from this place after 5 years.

No issue.. When you are gone its not your problem anymore..


Hope the change of job serves you well.. Good luck..