Earth faults are very hard to find, they come and go, so you have to monitor over an extended period.

>Hi Neil
>
>>Maybe there is a device in the building that has an earth fault and is livening up the reo in the concrete.
>>A Magnetic Flux Meter is the only way of finding the external flux source.
>
>Okay, I will get the wiring checked by the electrician. Thanks a lot or your input.