Compressor Trips RCD

[Newpark7]

Hi Everyone

Had to replace an old Re-wirable fuse board last week in a small industrial unit, replaced with a split load board, originally had the compressor wired into the RCD protected side and everytime the compressor started it tripped out the RCD.

I have since moved it to the other non rcd protected side & it works fine. The compressor is protected by a 32A MCB has two motors which start with a time delay (I.E. one motor starts & runs and then the other) to prevent overload. I measured the start current to be 38A and the current when running is 23A.

I know the compressor does not need RCD protection, Just wondered why the RCD trips?

Thank you

 

[ringer]

I know it's not an RCBO (or is it?) but can RCDs trip in overcurrent situation?
Presumably a time delay circuit of contactors is used to control the motors. Is this wired up correctly (N to E fault on contactor circuit possibly?) Have you put a clamp round the earth to measure the leakage?

 

[Newpark7]

Hi

Thanks for the reply no I haven't put clamp around earth that's a good idea. I also didn't think an rcd should trip on overload. Unfortunately I didn't get time to test contactors etc.

 

[ringer]

Do you have another RCD you can substitute - thinking possible dodgy (in overcurrent) RCD. I take it the MCB remains closed when the RCD trips.
It may be possible initial contactor is shorted to earth so is then operating (but under fault conditions) and the fault is then taken out of circuit by timer action before the fault becomes apparent. Total guess this - only you can tell what the fault really is. Do let us know.