Possibly dangerous wiring

[<me9]

Yup.

[<me9]

It is dangerous as I found out when working on my upstairs circuit (moving a ceiling rose requiring discvnnection of the cables, the neutral of which was then live from the downstairs lamp.

The air became blue in more ways than one.

[<me9]

As I found out! The neutral was dissed between the CU and where the borrowed neutral came in, resulting in working on a live cable.

[John Rumm]

Understandably...

I think one has to assume when working of two way switched lamps of unknown provenance that *all* circuits that might be related need to be switched off to be considered safe.

[Pete Verdon]

I'm possibly more paranoid than most, but when I'm working on electrics I generally kill the whole house, just to be sure.

Pete

[Trevor Smith]

I know it's wrong to borrow neutrals from other circuits but all neutrals are commoned in the CU so how does that work. Trevor Smith

[The Medway Handyman]

I'm paranoid as well TBH. I check the live with a volt stick, turn the circuit off & check again with the volt stick. I now know for sure that (a) the volt stick works & (b) that the right circuit is off.

Thanks to Owain IIRC.

[ARWadsworth]

6181Y (blue) cable is what you should use.

Adam

[ARWadsworth]

In the OPs case if he turned the upstairs lights MCB off and the landing light (which is fed off the downstairs MCB) is in the on position then the neutral cables on the upstairs lights will be carrying the landing lights current.

Normally you would not notice this but when the bathroom light is taken down it will break the the neutral connection to the CU that the landing light is using and one of the neutral cables at the bathroom light will become live.

ie you have a circuit that looks like this

downstairs MCB>switch>lightbulb>neutral cable(not connected to neutral anymore) so all that stands in the way of you and live MCB is a lightbulb (which will be only in the order of 40ohms)

Adam

[Cicero]

========================================== Thanks for that information - I assume that it's double insulated like this:

've just been to Screwfix to look at their 'Conduit cable - 6491

1.5mm' which is only single insulated despite its name.

Would it be safe to use a single core stripped from a standard 1.5mm T&E? I would need to run a length of about 10' / 3 metres. If not I'll have to get some from a proper supplier tomorrow.

Cic.

[John Rumm]

Tricky getting it in less than 10mm^2 though...

That's because it is intended to be installed in conduit - which will provide the overall screening required.

It would be better to leave it in the T&E and just not use the other core.

[Cicero]

>

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I was hoping to get the double insulated if possible because there's already some (red) in the system which I would like to match. I assume from the appearance that the outer layer of insulation ('sheath', I believe) is more for mechanical protection than electrical.

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This looks like the best prospect as I don't want to risk damage whilst drawing through the metal conduit. I'll try the local place in the morning for sheathed single but if it's not readily available I'll follow your suggestion even if it means exposing the conduit.

Cic.

[<me9]

I was working on a single circuit (so I thought), a bedroom light. I had become cheesed off at bumping into the light whenever I put my jumper on, so wanted the light moved.

According to the CU, it had been installed by a well known company with NIC/EIC memebership.

However, I no longer give credence to anything I haven't installed/inspected myself, and even then.....

[<me9]

Unless I'm absolutely certain, I do now. Sometimes it may be worth isolating next door too!

[ARWadsworth]

>>

Is there not a airing cuboard you could run the cable down? It can be very tricky getting an extra cable down condiut that already has cables down it. Silicone spray can help ease things through.

Adam

[Trevor Smith]

I see, when you explain it it makes sense, a floating neutral on a switched on circuit will always be live through the load. Thanks for that. Trevor Smith

[John Rumm]

Ah, sorry did not realise you had conduit. In which case, you can use ordinary singles without the double sheath - that will probably draw easier than a T&E (which can be a bugger to get through conduit).

[Cicero]

========================================= No, I'm afraid this is the only the only feasible route without a long convoluted cable run. There appears to be plenty of room in the conduit but I'm aware of the risk of getting new cables stuck in existing cable. It's really going to be a case of 'suck it and see' but worth it for the end result.

Cic.

[Cicero]

========================================= Welcome news! I'll go back to Screwfix for their item in the morning if I can't get the sheathed variety from a specialist place. It seems a bit over the top to buy 100 metres when I only want about 3 metres but that's the price of DIY. Hopefully, success tomorrow.

Cic.

[Pete Verdon]

I imagine TLC would cut a length for you, if you have one nearby (or the time to order it).

Pete