A dangerous experiment?

[Timothy Murphy]

Several (but not all) lights on one lighting circuit in my house have stopped working. I asked on this newsgroup about the problem, and received many useful suggestions, particularly pointers to the circuit diagrams at

?title=House_Wiring_for_Beginners#LightingI've worked out that there must be a break in the connection between 2 of the lights on this circuit. Unfortunately replacing the connection seems to require a lot of work - either removing some of the wooden ceiling between the 2 lights (about 4 metres apart) or pulling up the carpet in the room above, and removing some of the floor-boards.

We have visitors staying next week, and one of the rooms with no light is the bathroom, so I am thinking of effecting a temporary kludge.

What I am thinking of doing is removing the ceiling rose on one of the affected lights, and adding a temporary connection to a power socket.

Is this a dangerous experiment?

[NT]

Lets look at the issues.

It would move protection of the faulty circuit from the 5/6A lighting mcb to the 30/32A socket mcb and 2-13A plug fuse. If the broken circuit reconnects, the whole lot would then be on plug fuse in series with 32A mcb all in parallel with a 6A mcb. Its certainly not compliant.

If fixed securely, there is then risk involved if the system were worked on by people aware of the setup. Wrong plug fusing is relatively minor in that 1mm cable can manage on 13A using, albeit with prolonged disconnect times an issue.

If the CU is split circuit, there would be an added risk that one side of the CU would feed power to after the switch on the other CU side, which is a more significant risk than the other things.

Some people dont mind such risks and legal questionables, and there are surely worse setups in use. I couldnt recommend it.

NT

[Rick Hughes]

Yes .. you are mixing up power & lighting.

If you totally isolate the particular lights so there is no way power & lighting circuits are or can be missed up, then you could think of it as if a free standing lamp, and protect via a 3A fuse.

The danger of course is that the temporary fix gets left in place and in some years in future someone goes to work on lights having killed light cct at CU, and does not know there is separate power feed .... not good news.

So the answer is can you do it, yes, should you do it .... no Can you do it safely ... yes ...if you can totally isolate all of the lighting cct ... but as you are unable to gain access (or you would fix the problem) it would seem unlikely that you can be sure that you would not be feeding 'power' into any other lighting cct. Are all your sockets on an RCCD ? then you really should not go ahead with this IMHO

In my house all AC outlets & lighting is RCCD protected

Why not simply give the room a couple of standard lamps plugged into AC sockets until you can get around to fixing.

[Timothy Murphy]

Thanks very much for your response. I know what I am planning is "non-compliant". It is intended as a purely temporary expedient.

I'll certainly remove everything I put in before calling in an electrician. I've a feeling there may be some smart way of mending the circuit, without involving too much dislocation, and I'm asking around to see if I can find a clever electrician.

[Nightjar]

A battery operated light, as sold for cupboards etc., would be the safest option.

Colin Bignell

[Timothy Murphy]

The room most affected is the bathroom; and putting a standard lamp in there seemed to me more dangerous than what I am suggesting.

[Rick Hughes]

Then if it is a bathroom ... that is a non-no

Personally I would not advise a bodge on any bathroom cct .... do it right or use battery powered lights until you can .... B&Q sell ones designed for lofts & under stairs ...

[Newshound]

One of the meaty "work lights" would be even better. I had a couple of these and used to swear by them (bright, and long battery life)

light

but they both died on me. Can anyone recommend a bright LED work light with a decent sized battery?

[Jules Richardson]

Was that a typo? A non-no would be a yes, a no-no would be a no. ;-)

[Bill]

In message , Timothy Murphy writes

Did you work this out in theory or have you actually been into the fittings and tested?

If you haven't been into the fittings then it maybe as simple as a loose screw allowing the feed to the next light to become disconnected. Much quicker to fix than your proposed temporary solution. Also rather a lot safer :-)

[Jules Richardson]

Do you think that the cable has just broken somewhere along its length for some reason - or do you mean there's a hidden junction box somewhere with a faulty connection? (over here junction boxes have to always be accessible, but I don't recall if that was a UK requirement)

(cable breaks just seem quite unlikely, that's all, and I'd expect the fault to be at a terminal, switch, fitting etc.)

It seems unwise to me without being able to inspect the actual fault - you don't know what might be touching what in the non-working section, and feeding power into it might have interesting consequences.

If you can see the fault and be sure you've completely isolated it then it might be a different matter - but personally I'd be looking at other ways of providing lighting as a temporary solution until I could fix things properly.

cheers

Jules

[Grimly Curmudgeon]

If it's a bathroom, I suspect he's poo-pooed the idea.

[The Medway Handyman]

IANAE but I was thinking along those lines as well. The bathroom may well be the last light on the circuit?

[Jules Richardson]

Well, rodents might do for a cable, or it might get squished by a settling house, or some form of induced vibration (assuming not properly affixed) over time etc. so I don't think a cable break's impossible - just that other things are more likely culprits.

I missed the original thread on this, so I'm not sure what was advised there or what the OP has checked.

Hmm, the post mentions 'one of the rooms with no light', so it sounds like there's more than one light affected - but as it's most likely a radial circuit (does it *have* to be in the UK? I'm not sure) then anything downstream of the fault will be dead.

If it were me, at the very least I'd disconnect the damaged section at the last-working fitting sharpish though, just so it's not supplying mains on a wire that might have a bare end knocking around somewhere.

cheers

Jules

[<me9]

Probably a light fitting has been replaced and the loop through or neutral not connected correctly.

[Timothy Murphy]

Thanks for your (and all the other) responses. This was in fact a purely theoretical deduction ...

I've looked at all the ceiling roses that are affected, particularly the last one working and the first one affected. The connections on them all look fine to me.

Unfortunately for my experiment, the ceiling roses are not as in the online diagram at

elsewhere online. Each ceiling rose has two terminals on the ceiling side, one of which has 3 incoming wires attached to it, and the other has 1 incoming wire attached to it. The two wires to the light are attached to the two terminals underneath the rose.

The only way I can make sense of this is that the single wire goes to the switch and thence to the live supply, while the 3 wires are negative and go to the next light, the last light and possibly the switch?

I should say the wiring is fairly old - 25 years - but was installed by an electrician who I am sure would have followed whatever rules were in place at the time. (He worked for the electricity supply company.) I checked in an electrical store here, and the ceiling roses sold now are as shown in the online texts.

Any advice on this setup gratefully received.

But I'm tending to the advice offered by several posters to get a temporary battery-operated light for the bathroom, probably from B&Q.

[John Rumm]

Same rule applies here - any screw terminal connection must remain accessible.

+1

Not only that, but if we assume the socket circuit has RCD protection (possibly aka GFI on Jules' side of the pond), then feeding a partial broken circuit sounds like a recipe for a tripped RCD due to having unexpected return paths on the lighting circuit.

+1

[John Rumm]

Could you clarify what you mean by "Ceiling side" (in fact a photo would help)

If following a "loop in" style of wiring (which there is no guarantee that it is), then this sounds plausible... probably neutral in, out, and to lamp.

One terminal with one wire? Aside from stopping it waving about, that does not sound quite right... is the terminal attached to anything else?

Which two terminals underneath the rose?

I take it we are not talking about your stereotypical ceiling rose:

The only way I can make sense of this is that the single wire

You don't usually have a neutral at the switch unless doing the "loop through switch" style wiring shown here:

is also the rarely used "Single and earth" lighting circuit:

I should say the wiring is fairly old - 25 years -

It sounds like you are going to have to be a bit methodical and do some detective work. Look in a couple of roses and see if they are the same. Same goes for a couple of switches, see if we can figure out how this all hangs together.

I would not be inclined to go patching anything together with outer circuits until you are *sure* you know how it is currently wired, otherwise there may be any number of unpredictable and possibly dangerous outcomes.

[Brian Gaff]

Its on a different circuit. cannot you simply get a portable led chargeable light and shove it in there for the period.

The most common fault condition from memory is cooking of the connections in the rose and some kind of lack of continuity caused this way, after all, wire hardly ever fails, its normally connections that get dirty, fall to bits etc, unless you have mice in which case look for decomposing electrocuted mice!

Brian

[Brian Gaff]

Not so much wired as weird.

Brian