Isolate lighting circuit after leak?

[Vicario]

My neighbour's kitchen extension (flat roof) has a leak and there is visible cracking and water staining on the ceiling. One of the water stains is very close to a light fitting but so far the lights still work. The kitchen lights are on a breaker labelled 'lights downstairs' - it's a dual RCD board, so if that trips half the house will go off. He's asked me to ask you guys if it's prudent to switch off that particular breaker (he can manage with plug-in lights downstairs for a few days) or should he leave it and see what happens? The main issue is that the house alarm is on the same side of the CU as these lights, and it's a pain to re-set if it loses power. Is there any effective way of isolating this particular circuit without opening up the CU, which I realise is a no-no for non-electricians. Roofer is coming this week to have a look, by the way.

 

[ETAF]

switching off the breaker wont stop the RCD from tripping if water gets into the circuit
depends on whats in the roof and what the water can short out - if its Just a cable direct to the light itself , then maybe disconnecting the light and isolating the cables - so the water cannot short anything out - if there is a junction box in the roof itself and water can get in and short out then switching the mcb wont stop the earth leakage

shorting earth to neutral for example - its not just the load

 

[Vicario]

That's what we fear - it's quite a big leak. Is the interim answer to disconnect the entire circuit at the board? We have a very good local electrician and I imagine it's not a long job.

 

[pete01]

That's the answer, its a 2 minute job.

 

[Murdochcat]

If it’s looped at the switch it might be easier as it would allow the remainder of the circuit to stay live

What type of light fitting is it?

 

[ETAF]

maybe some photos would help of switch and light fitting

 

[ericmark]

The ceiling rose often works with a loop in and out This often means you can disconnect the ceiling rose in question at the ceiling rose before it. Unlike sockets, the lights are not normally wired as a ring, so what can or can't be disconnected depends how the lights are wired, and if the kitchen is at start or end of the radial circuit.

As to if a DIY job, well there is no single qualification that makes anyone an electrician, it is down to you to if you feel you know what you are doing, but since you have asked the question, I would say you should not be doing the work, but to know easy enough to do, may mean prudent to get some one in to disconnect it.

Once electric arcs, it forms a carbon track, so it is better done before it all goes wrong. But not done at the light which may get wet, but the light before that.

 

[Vicario]

All very useful stuff, so thanks everyone. I'll post here when I know the outcome. A question from me now....I have very much the same setup and was wondering if it's a big (=expensive) job to change a dual RCD board to RCBOs on every circuit to avoid this kind of worry.

 

[Murdochcat]

All very useful stuff, so thanks everyone. I'll post here when I know the outcome. A question from me now....I have very much the same setup and was wondering if it's a big (=expensive) job to change a dual RCD board to RCBOs on every circuit to avoid this kind of worry.

Depends on the current board (photo please)

 

[Vicario]

 

[Murdochcat]

That looks like a metal CU - it’s a shame the installer didn’t fit the RCBO version

 

[Vicario]

Yes it is metal. So would it be possible to convert the circuits to all RCBOs? He left a spare at the far end which is not on an RCD - would that have been for a future EV charger if I remember correctly?