RCBO trip.

[Munders]

Got a large rewire ongoing at the minute. Owner wants to use current sockets alongside the new board as he’s living in one part of the house whilst the builders are in. Today the old supply was disconnected and whilst cutting through an old cable not connected to any of my new legs the RCBO tripped on the new lights. I tried it several times and same result. It’s not a problem, I’m just curious why. The only thing I can think of is that both the old main earth and new were still connected at the meter. If that is the case then why only the lights and nothing else.

 

[Pretty Mouth]

I'm with PEG on this one, I can't see how this could be happening without there being some kind of connection between the old and the new circuits. A segregation test between them is in order.