borrowed neuterals

another lectrical Q i'm afraid.

This time my bungalow, other day i took the floor boards up in the upstairs to get at the light wiring, as i wanted to change the switch layout in the living rooms (was origionaly a normal bungalow, but when changed to a dormer, the living room's light switch ended up behind where a corner sofa naturally goes due to a door being blocked up)

anyway, everywhere on the lighting circuit i found junctions (made from uninsulated terminal block) at various socket cables neuterals, living and dining room lights were using the neuteral from the upstairs sockets, live fed via the lighting circuit, which still had a good neuteral but wasnt used, so f*ck knows why it was wired like this,

i wired the 2 lights off a double switch 'properly' using the origional neuterals in the lighting ring, and all works, so i have no idea why these lights were on a borrowed neuteral from the ring main.

any idea's? and what implications does this have for the rest of the wiring? thinking about the RCD, but i'd have expected it to be tripping all the time due to the neuteral from the lights going back down a rcd protected neuteral, but it didnt and doesnt, works off the test button fine,

theres also a circuit in the breaker box that has me stumped, before the RCD there's the 6 amp breaker for the lights (1950's bungalow, single lighting ring for the entire house) and also a 16 amp breaker, this one feeds a spur, but where it goes and what it does i don't know, any ideas to what would want to be unprotected by an rcd that's not a lighting circuit??

the driveway flood light runs off the garage lighting circuit, the garage has a breaker box which is run as a spur from a 32 amp breaker after the rcd, there an unused 32 amp rcd (was still connected up, but found the cable in the floor upstairs taped up) that i've found out was for a lecky shower, but again that was after the RCD as expected,

The kitchen only has 2 sockets in it, and they run from the ring main breaker, there's never been an electric cooker here, and 16 amps is too low for that, no outbuildings or owt,

i just can't think what would want a 16 amp non rcd protected breaker, the place has an alarm, but it's run from the ring main and hence is rcd protected, combi boiler is powered by the ring main too.

Reply to
gazz
Loading thread data ...

if the 2 ccts feeeding the lighting are both run off the same rcd, the rcd would behave. If not, it looks like you would have another problem.

immersion, outdoor feed, garage, etc. Just turn all except that one off and see what you've still got running.

NT

Reply to
meow2222

Independent socket in the garage for a freezer maybe ? Sometimes prone to nuisance tripping, and maybe some previous owner was away a lot ?

Arfa

Reply to
Arfa Daily

I would expect it to trip too, are you sure the live to the lights doesn't come off the ring too?

If it doesn't appear to and it still doesn't trip you have some other obscure fault.

Reply to
dennis

I would confirm that from experience. I regret to say that I did a similar bodge many years ago when SWNBO started off saying she didn't want a two way switch for a particular light and then changed her mind !! And I stupidly didn't wire it to allow for the female mind, and so had to borrow a neutral from 'somewhere else'.

When I changed the CU for a modern one recently, the RCD tripped every time that light was switched on which was not unreasonable when the 'somewhere else' was the upstairs power ring, now protected by the RCD. So a more acceptable re-wiring had to be undertaken.

The fact that your RCD is not tripping does suggest a further bit of abomination somewhere.

By the way Gazz, the spelling is 'neutral' not 'neuteral' - that's as bad as our George W and his 'noockalear' !

Rob

Reply to
robgraham

You shouldn't borrow a neutral. If you isolated the ring and broke the ring and a light was switched on you would get a shock.

Reply to
John

That's almost what happened to me a while ago working on some house lighting in the studio of a theatre with which I'm involved. There were two lots of lighting worked off two separate fuses in the same switch-fuse. I was replacing one set of lighting, working by the light of the other. I'd pulled the fuse (obviously) of the lights I was working on. As I disconnected one of the lamps I was suddenly plunged into darkness as the others went out...I could've got a serious belt if I'd happened to touch the neutral wire. There's no excuse whatever for borrowing neutrals. All this was in steel conduit. It would have been a doddle to provide proper neutrals. The installation would have been some 10 - 15 years old at the time.

Reply to
Frank Erskine

Thanks for confirming this Frank. I uncovered a situation at a my daughter's house when I was decorating - I was curious to see why there was a plastered over channel from a wall light to a plug socket. It turned out that the wall lights got the live from a switch (converted from one gang to two gang) on the lighting circuit and the neutral from the ring main. Whilst I was concerned I hadn't fully appreciated to danger until I asked this group.

I now have a large warning label on the fuse box - until I get around to getting a re-wire.

Reply to
John

i think George W actually says "nucular" rather than 'noockalear'; he swaps two syllables rather than adding a new one.

Robert

Reply to
RobertL

is it OK to borrow an earth?

Reply to
George (dicegeorge)

Not always.

Reply to
dennis

a whole one?

Reply to
The Natural Philosopher

Sometimes, but not usually. Every circuit must have a circuit protective (earth) conductor, its CPC. One CPC can serve several circuits although normal practice is to run a separate CPC for each circuit, except where several circuits are run together in metal conduit or trunking which serves as a common CPC for them all. The CPC for a ring circuit must also be in the form of a ring, again unless metal conduit is used.

Where an overcurrent device (fuse or MCB) is providing the earth fault protection each CPC should follow the same route as the line and neutral conductors, staying in close proximity to them. Effectively this applies in all TN-earthed situations, even where RCDs are fitted for additional protection.

In a TT installation, where RCDs provide the automatic disconnection of earth faults, the close proximity requirement is removed, so I guess you could say that borrowed earths here are OK. Don't forget though that CPCs which aren't part of a cable and aren't protected in conduit or trunking are subject to a minimum size of 4 mm^2 (as for supplementary bonding) on grounds of mechanical robustness.

Unlike with neutrals, there's no objection to cross-connection occurring between the CPCs of different circuits and this often happens in practice where bathroom supplementary bonding links the power, lighting and shower CPCs, or where two lighting circuits meet in one back box, for example. Such cross-connection is generally beneficial since it reduces earth fault loop impedance and can reduce the fault touch voltage (like supplementary bonding).

HTH

Reply to
Andy Wade

aha, thanks Andy, so CPC means circuit protective conductor...

An electrician said something about the existing grey cabling in this house having a too thin earth wire- (there are 2 fat wires going to 2 fuse wire boxes to feed distant rooms) so should i take 4mm earth wire parallel to them and connect both ends, or is there a better fatter earth wire to add- as the cost of the wire is trivial compared to the cost of my time?

(I have a little mains tester plug with 3 red lights and at one circuit there was no red light on the earth so it was there that i borrowed an earth as a temporary solution)

Reply to
George (dicegeorge)

Probably 2.5mm^2 with 1mm^2 cpc. Later stuff has 1.5mm^2. It's not (quite) compliant with current regulations for IIRC fault protection, but only if used with rewirable fuses and in some rare circumstances. 32A type B MCBs would be ok for a ring with it.

Reply to
<me9

HomeOwnersHub website is not affiliated with any of the manufacturers or service providers discussed here. All logos and trade names are the property of their respective owners.