compressor / electrical problem

[Northdude]

I recently replaced an aspira compressor to a dairy cabinet, cabinet ran for 2 days ok then tripped main breaker on db board. Tested electrics on compressor electrics (relay and cappys) and found live to be down to earth, disconnected live and neutral (mains in) to compressor electrics and found live still to be down to earth meaning problem with compressor as relay and electrics box is not earthed,was about to remove electric pins off compressor to test compressor on its own when i suddenly lost continuity between earth and live? checked cables etc from electric box to compressor and all is fine, switched on cabinet and all is ok untill 1 day later then problem reoccurs, all electrics tripped and compressor is down to earth again?? This has me totally baffled as of past experience if compressor is down to earth then compressor is down to earth full stop but this has happened 4 times now and I dont have a clue why, if windings in compressor were gone how could it suddenly be down to earth then suddenly be ok?? I have tested my meter and it works fine but i seem to loose continuity between live & earth when i check with my meter, have never came accross this problem before so if anybody has any ideas it will be much appreciated.I also checked resistance on compressor pins (single phase) and got 12 10 4 which isnt far off but also isnt right? Thanks

[nike123]

You need to check compressor with mega ohm meter not with universal instrument for windings to earth leakage or any breach in windings insulation.
But, if you in any point measured that it has connection to earth lower than infinite with universal instrument, than it is faulty compressor.
Of course, you should pay attention that your connection terminals are clean and dry.

[rnine]

Does the compressor have an internal overheat protection device ( klixon ). If so, the klixon might be causing your earth fault on activation. Longshot I know. But it's worth keeping in mind..

Rnine

[wilks]

as nike said , id use a mega , this in effect tests the windings under load condition . Fault my only occur when windings are hot ( eg under load ) hope this helps .

[nicolacozma]

Sometimes it`s happend that there is a problem with the insulation of the windings of the compressor.
If the compressor remain a long time stopped and the refrigerant liquid creat a mixture with the oil then we will have a low insulation resistance and the protective current device will trip out.
Anyhow for this kind of problems the solution is to replace the compressor with a new one.

Regards,
Nicola

[Northdude]

Thanks for the feedback, replaced compressor again and all seems well !!

[nike123]

Thanks for the feedback, replaced compressor again and all seems well !!

Wait for two days to say that!