Hi guys, need some advice please. I've got a problem on a French 3 phase CU. Basically the 3rd phase rcd trips when the boiler circuit on the 2nd phase is on whilst a sockets and lights circuit on the 3rd phase is on. If i turn off the sockets and lights mcb (there on the same circuit) then there's no trip and vice versa. Its only just started happening recently aswel I've been told and the client said nothing has been done to the installation. I've checked all the fittings for decent connections and everythings fine. I can't quite understand why its two separate phase circuits are affecting each other. Any advice will be gratefully welcomed, thanks.