Pinched neutral off upstairs lighting for landing light

[Michaelsf90]

I have installed a new mains with rcbos on my house. Rewired upstairs lighting and I noticed they'd borrowed a neutral from upstairs lighting when the landing light had a feed from downstairs lights. So I ditched the switch downstairs and the landing is fed by a switch at the top of the stairs. So to not have to chase the wall out I was thinking could I fish a feed and neutral up into the loft and connect the neutral to the landing light only. The feed will be in the joint box not doing anything. In the mains I would have two 1.5s connected onto that RCBO and neutral bar. I cant see any other way to be able to operate both switches without chasing walls out

Also should the mains have one large hole cut out the top instead of using several of the individual knock outs?

 

[Michaelsf90]

The landing light would then be fed off the downstairs lights instead of the upstairs lights which I had to do so the neutral wasnt borrowed

 

[securespark]

That's OK. I have deliberately wired some houses like that. If the upstairs lighting trips, you still have light on the landing.

 

[Taylortwocities]

What do you mean by a "new mains". IS this the consumer unit that you have replaced yourself?

 

[ericmark]

The Quinetic range of switches not cheap but saves having to run wires.

 

[Michaelsf90]

Yer. I'm an electrician. But I've never done domestic. I work at a hospital and have done for many years. I know eddy currents and all that carry on. I technically only need to run a neutral up to the landing light but I dont know what issues it could cause only having a neutral connected on a twin and one doing nothing. Which is why I said about connecting a feed but not doing anything with it. Just having it connected in the joint box but nothing coming off it

That's why I'm asking about the cables coming out the top of the mains through knock outs. Does it need to be one big hole. I would get the cable I'm running up to go through the same hole as the feed for downstairs lighting

 

[EFLImpudence]

Yer. I'm an electrician.

Right.

But I've never done domestic.

Therefore you won't be registered to self-certify (which means self-notify) so you should have notified the Local Authority before you started.

I work at a hospital and have done for many years. I know eddy currents and all that carry on. I technically only need to run a neutral up to the landing light but I dont know what issues it could cause only having a neutral connected on a twin and one doing nothing.

None.
Is that not just the reverse of the present situation?

Which is why I said about connecting a feed but not doing anything with it. Just having it connected in the joint box but nothing coming off it

That wouldn't make any difference, would it?

That's why I'm asking about the cables coming out the top of the mains through knock outs. Does it need to be one big hole. I would get the cable I'm running up to go through the same hole as the feed for downstairs lighting

I don't understand what you mean about the hole size.

"The Mains" is the actual electricity supply itself. What you are talking about is a "Consumer Unit" - a "Distribution Board" for you at work.

 

[Risteard]

A PVC/PVC single blue would be more sensible than a T&E.

 

[flameport]

cables coming out the top of the mains through knock outs. Does it need to be one big hole.

Individual conductors of a circuit must pass through the same hole in a metal enclosure.

Multiple circuit cables could go through a single hole, but as the top surface of a consumer unit needs to be sealed to at least IP4X, making one large hole isn't a solution as it will be rather difficult to seal it properly.

 

[JohnW2]

A PVC/PVC single blue would be more sensible than a T&E.

Is such an animal easily available in small CSAs? Maybe it is in your country but, over here, insulated and sheathed singles are commonly only available in sizes from 10mm² upwards, intended for (as often described as) 'meter tails'.

 

[bernardgreen]

http://www.doncastercables.com/cabl...ngle-Core-PVC-Insulated--PVC-Sheathed-Cables/

 

[flameport]

Is such an animal easily available in small CSAs?

https://www.cef.co.uk/catalogue/cat...sories-6241y-flat-single-core-and-earth-cable

Shorter lengths from other sources
https://www.ebay.co.uk/itm/1-5-mm-S...le-6241Y-Blue-Grey-PVC-PVC-Wire-/252492658607

and if a CPC wasn't required
https://www.cef.co.uk/catalogue/cat...area[]=1.50mm²&cross_sectional_area[]=1.00mm²
https://www.ebay.co.uk/itm/1-5-mm-B...181Y-Double-Insulated-Light-Wire/252492661945

 

[JohnW2]

I did say 'easily available'. Other (apparently) than for CEF, which other electrical wholesalers are likely to have it 'on their shelves' and, perhaps, more to the point (in this DIY forum), which source commonly used by DIYers (other than eBay, if they are prepared to 'risk' that!) could supply it in small lengths?

Kind Regards, John

 

[Michaelsf90]

Sorry if its getting confusing. When I moved in I decided to change the consumer unit. It's a wylex metal one. Their is limited room where it is so I couldn't fit a dual rcd board so I decided to go with rcbos. When I rewired the upstairs lighting I noticed they had borrowed a neutral for the landing light. The switch at the bottom of the stairs has the feed in. Then the strappers come up to the landing switch. Then the switch wire to the light. The neutral was took from the bathroom light. Now I know this is wrong

With being at the hospital I've been on the wrong end of a disconnected crossed neutral and it seriously hurts. When people have crossed essential and non essential circuits over

Anyway because I was putting rcbos in I decided to leave it on the upstairs switch only as it's at the top of the stairs. Disconnected the switch wire at the switch at the bottom of the stairs and made safe the switch wire in the loft despite it being disconnected at the switch downstairs. So now the landing light is off the upstairs circuit

But to get it so I can use both switches the easiest solution is to fish a cable straight up the cavity to the loft which someone has done before for the shower circuit and burglar alarm circuit, just to get a neutral up to the landing light off the downstairs circuit. I agree a single blue would be better but I have enough 1.5 t+e to do it. As long as I make sure the cable runs through the same hole as the downstairs lighting circuit cable already will that be ok? I know it's not ideal doubling up but I cant think of another solution without making a mess?

So it's ok I have my lighting circuits through one and my shower through the next, ring main through one and so on?

I will also get someone I know to test and issue a certificate so its above board

 

[Michaelsf90]

Also is fishing up the cavity frowned upon?