Run winding high resistance and tripping

[Drew]

Good day all,

I've got a aspera 3hp 404a low temp comp tripping a circuit breaker with a high resistance on the run winding , but not down to earth . This comp has recently been replaced and the previous comp suffered a similar fate. Will be checking acid levels.
the client is also having other gear in his kitchen fail.
any ideas what could be causing this high resistance. It's not shorted or open circuit but just 4 x higher than it should be?

[install monkey]

whats the name plate say its max running current? u say the run winding is higher - so were talking about a 1 phase unit- are the external's ok,correct sized capacitor, relaywired correctly
oil level ok, crankcase heater operational- start/run wires on correct pins
maybe weak breaker

[moideen]

Good day all,

I've got a aspera 3hp 404a low temp comp tripping a circuit breaker with a high resistance on the run winding , but not down to earth . This comp has recently been replaced and the previous comp suffered a similar fate. Will be checking acid levels.
the client is also having other gear in his kitchen fail.
any ideas what could be causing this high resistance. It's not shorted or open circuit but just 4 x higher than it should be?

do you mean high run wind resistance compare to stat wind resistance? have you checked the resistance between run wind and start wind before starting the compressor?

[Drew]

Yes it's a single phase unit. The run ( main) winding has gone up. Initially they (start and run) measured something that I thought made sense, now that it's tripping , the start is still the same but the run winding is in the 90's ohm. I would have thought that if it's tripping the cb without even trying to start it would be down to earth. I've applied double the applied voltage with the insulation resistance tester from earth to common, run and start and not a flicker on the gauge. We changed the electrics when we changed the compressor ,I also rechecked my live , neutral connections and made sure my compressor connections where good and their connections to the relay.
If the resistance has increased and nothing's shorting what's tripping the cb? My ampemeter reads only 0.3 amps before tripping, I've tried to run it off a different circuit with a separate supply. Same result. So something is wrong with the winding and a similar thing happened to the previous comp.
gotta send the comp back to suppliers so cannot wait for their diagnoses before fitting next dome after system cleanup.

[Rob White]

.

90 ohm's divided into 240 volts = 2.6 amp
your amp meter shows 0.3 amp so it's not tripping on locked rotor amps?

If the resistance has increased by X4 like you said in your earlier post then
the resistance should be about 22 ish? 22 divided into 240 v = 10amp?

Did you check the earth with a proper insulation tester? (you said you did)
If the earth is sound then the winding could have failed and it only becomes
apparent when it gets hot, when it runs up.
How long after start up does it run before it trips?

Regards

Rob

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[install monkey]

whats the model of the comp and make??

[Drew]

The comp doesn't run at all. As soon as I turn on the circuit breaker it trips, no thing else on the circuit . Tried others. Insulation tester seems ok. As my apprentice turns on the cb I can hear a very faint pop from inside the comp. their must be short happening only with the 240v is applied but is clear when the insulation tester is used?

[Drew]

Checked the oil today after fitting a brand new cond unit to the site on the insistence of the client and my boss after explaining all my reservations about the fault. The oil is not acidic ,it looks good ,smells good, but is showing a slight conductive reading with the IR tester 50 Megaohm @ 500v. as opposed to new POE oil showing me infinite. Dye had been added to the system. I am still not picking up any earth readings from the windings, not even the 50 mega ohm when the oil is in the sump. Wouldn't the windings be slightly oily and if the oil is slightly conductive i should be picking up that reading . anyway that's just something else to think about.
So i dont think its failed due to an acidic system.
Back to voltage surge wihile unit in running mode? Klixon wouldnt save the compressor from a surge. It would have been a sudden thing without acid been formed?

[Rob White]

.

If the compressor has a short on the winding it will pop the breaker
but the resistance will be quite low (not high like yours is)

So you just mark it down to one of those things

Regards

Rob

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[FreezerGeezer]

What Rob said, I thnk. But, have you checked the power supply wiring from the MCB to the system? It's always possible that's got a fault.