Electrics question

[RizzoTheRat]

As part of some extension work, the builder ran some extra cabling up to my top floor and the electrician re-did my consumer unit, from 8 breakers to 12, in blocks of 4 each with their own larger breaker.

The builders then fked up the wiring and had the top floor light only controlled by the top floor switch, not on a two way with the floor below. Having cut some holes in the walls to get at the wiring they've now got all the wires in, but as soon as you put power to the top floor light it trips the breakers for blocks 1-4 and 5-8, but not 9-12 which the other light on the top floor is running on. They're now scratching their heads and waiting for the electrician, who never seems to be available.

Do the neutrals go through the breakers as well? The only thing I can think of is the stairs lights are all getting power from 8, but the upstairs neutral went in with the 9-12 block. Would connecting a live from one block to a neutral on another block trip the breakers?

Consumer unit looks like this if it helps (labelling in Dutch)

[finlo]

You've most likely got the live coming via one RCD and the neutral via the other causing an imbalance and that imbalance is how RCD's determine a fault.
You need to get both L and N fed from the same circuit.

[Belle427]

Known as a borrowed neutral in the trade and that seems the most likely.

[RizzoTheRat]

So is the fix to have to run another neutral, or can they be linked?

[finlo]

RizzoTheRat said:

So is the fix to have to run another neutral, or can they be linked?

Linking them is most likely your problem, you need to ensure that both the L and N are from the same circuit not one from upstairs and the other from downstairs.

[RizzoTheRat]

The problem is going to be getting one there. We had a top floor extension, and they ran new power up there as we wanted a water heater, so I think everything on the top floor is now on the new circuit, except the power to the light which now comes from the switch on the floor below. Wait for the electrician I guess. Cheers.