Copeland scroll blowing

[lorano]

Hi guys

Looking for a second opinion here.Looking at my local pubs beer cellar.As soon as you turn the isolator on the compressor starts for a split second then trips the breaker.I replaced the power cable as it was knackered thinking it could be due to bad insulation but unfortunately it tripped again.Its a 3 phase copeland scroll.Ive check the windings to earth and they're fine,getting 7.5ohms on each winding and getting all 3 phases out the contactor.Im certain the motor is partially siezed but dot want to order up a £600 compressor only to find it was something I over looked.

[frank]

Did you measure the insulation resistance to earth with a megger type meter or just your multi meter?

[lorano]

Just a multi,don't have a megger:-(.Cant even get an amp reading as it goes off to quick.The very last time I reset it and switched the isolator on it didnt even try an start just tripped the breaker.Normally I would just condemn the compressor but the fact it tried to start is making me think twice.Its dead now right enough:-(.

[Chillin4alivin]

Disconnect wiring at compressor motor connections and fit into a connector block and switch on power. measure your voltage to see if your phases are balanced on the connector block. If they are and all else seems ok then its more than likely the comp. I would also check the mains breaker....is it a RCD?

[install monkey]

testing windings to earth without the use of a megger is pointless- test winding resistance, phase to phase with a multimeter no problems, i hope the 7.5 ohm was winding to winding if not your pot is deffo goosed

[Magoo]

Totally agree install monkey.

[Rob White]

.

You need to prove if it is electrically sound as the others have said
and as the others have said an insulation tester is the tool for the job.

If it was seized it would take a few seconds to trip maybe as long as
10 to 15 seconds if it had a large motor rated overload on it.

As others have said isolate the electrics at the comp end and then run,
if it trips the electrics are faulty.

Rob

.

[lorano]

The 7.5ohms was winding to winding and I did disconnect the wiring from the compressor and had all 3 phases when the contactor pulled in.

[Rob White]

The 7.5ohms was winding to winding and I did disconnect the wiring from the compressor and had all 3 phases when the contactor pulled in.

Winding to winding seems good but you need to winding to earth.

Rob

.

[bjkmiami]

Hello Iorano,
well you are saying that you have checked the windings to the ground and it was 7.5 ohm. so it seems like you have a shortage and a bad news!!And usually it is hard to catch the contunuity problem with multi meters since they send a low voltage through the loop and you may end up seeing some resistance alhough you have a shortage somewhere.In your case you already had very low ohm(to me below 50 is not good).And if you decide to check it one more time with a megger make sure you set the voltage on the megger 2 or 3 times the nominal voltage of the compressor.And my personal opinion, megger is the best way to check the insulation with the right voltage applied!!!!
good luck...