Consumer Unit query

Unhelpfully, i suspect the answer is "it depends". According to the exact routing of your hall stairs and landing wiring, I expect some neutrals have got linked which would have been no problem at the time but now you have the infernal RCBs fitted, this is causing the the tripping. By careful disconnection of wires in the switches ( mark everything and make notes!!) You should be able to deduce the way it has been wired and work out where the neutral bridge has occurred. Quite what then to do about it depends on where you can pick up a neutral of the right type. Yes your sparks was correct in what he did otherwise at commercial rates it would have cost you dear to rectify it. But reading your other posts I guess you possible have time to do this yourself and if your 'Active DIY' skills extend to electrickery then it should be do able. A logical approach and reasoning skills ought to sort it out. NB there are two distinct method of wiring two way switched lighting and it would be worth looking up both (internet search is bound to find them) before starting to map your installation. If you have a 3 switch system it can be even more fun! Good Luck Bob

I came across this twice last week when I was swapping CUs.

Your problem is that the landing light is taking it 230V from the downstairs lighting circuit and is taking is neutral from the upstairs lighting circuit. It is called a borrowed neutral and can leave a circuit live that you think you have isolated.

Strictly speaking the electrician should have put both circuits on the same MCB as well as the same RCD.

You only solutions are.

2) Take a live from the upstairs circuit to the (almost certainly but it would need to be checked) downstairs lightswitch. That will probably mean chopping into walls.

If you have an airing cupboard you can use it to run a cable inside to the loft then option 1 is the way to go. You could DIY it.

Adam

Thanks for that Bob - good advice. I'll do a bit of research and then take a look at the switch wiring. There are just two switches for the landing light - one at top and one at bottom!

Ret.

I'm a little confused here. I take it that 1) and 2) are 'options' and not two steps that have to be undertaken together? Option 1) should be fairly simple, whereas option 2), as you point out, would be a lot more problematic. Unfortunately I don't have an airing cupboard - I recently removed it and replaced it with a shower cubicle when we had a new combi installed! I do, however, have an internal boxed-in main soil pipe and that may be an alternative route for the neutral.

Ret.

Sorry. Yes they are options. Do one or the other. Do not do both:-)

If you can drop down a boxed in soil pipe then do it. Any neutral from the downstairs lighting will do. Use a juntion box if you have to. 1mm or 1.5mm

Adam

Thanks Adam - most helpful.

Ret.