Newbie: Unusual? Lighting Wiring

[news]

Hi,

I was about to replace a what I imagined was a simple light fitting (done it many times before) obviously expected L N E wiring, instead on undoing the old fitting I found a total of 3 cables each with a red and black (live and neutral?)

all three red wires go into a connection on the old light fitting, 2 black cables go into a connection and a single black cable goes into a connection.

Unfortunately the fitting does not mark LNE so I find myself completely lost. I obviously assume that red is live but unsure of what is neutral and what is earth. Is this a standard arrangement (it is wiring from a 1980's extension) and can anyone give me an explanation of what to do now and how to identify the cables!

Many Thanks

Chris Essex

[Bob Eager]

This is a very common (and normal) situation.

What you have is a power feed coming (ultimately) from the consumer unit. One of the cables will be this (line and neutral from consumer unit). The power feed then continues to the next ceiling rose, the next, and so on, until the whole of the lighting circuit is finished. The last rose will thus have only two cables. This is obviously not the last one!

So, the third cable goes to the switch. Beware - both wires (red and black) are really live, but the black one will be live only when the switch is on. So the third red will be line to the switch, and the third black will be line back from the switch, to the actual bulb. Technically the ends of this black should be sleeved or whatever in a red colour.

One in, one out, one to the switch. All line.

That is to (a) connect the incoming feed to the outgoing (to next fitting) feed, neutral. It also provides neutral, via that terminal, to the bulb itself.

That's the return cable from the switch and will be live when the switch is on.

In addition, all the earth wires should be bare (but sleeved green/yellow) and connected together. This terminal also gives an opportunity to earth the fitting, if it requires it.

Very standard.

You can deduce which is the switch cable, from the above. It doesn't actually matter about the other two; no need to differentiate them.

Now you know what they all do, you should hopefully understand how to replace it. If not, get a sparky in!

NOTE 1: This all assumes it's correctly wired. NOTE 2: For 'bulb' read 'whatever the light emitting device actually is'

[Sugar Free]

Why did you "obviously" expect this?

That said, it's what you've got.

That's more normal, yes.

It is called three plate wiring, and is by far the most common type of wiring in UK lighting circuits.

Yep. There'd probably be a bang if they didn't.

That'd be Live feed IN, Live feed OUT, and Switched Live.

The two black wires are Neutral Feed IN and Neutral feed OUT.

The single black wire is Switched LIVE and should be sheathed RED at both the fitting AND the switch.

Standard ceiling roses generally don't.

But then, they weren't designed with people with no idea of the work involved in mind. They were designed to be fitted by electricians.

have lived to tell the tale.

One simple rule where electricity is concerned -

- never assume. It is idiotic in the extreme.

You'll be telling us next that all black wires are neutral, by assumption. By that reckoning, you just got a belt off the fitting, since you also assumed it was switched off, and was, in fact, not, and felt it safe to play with all the black wires you mentioned.

You see why electricians go to college to learn about these things?

Earth would be all the (no doubt) missing or bare wires connected to the big terminal opposite the three plate arrangement you described above. There should be three wires.

Yes.

See above, and at the least, buy a book on electricity.

[Mungo "two sheds" Toadfoot]

[Old Bill]

As others have said, this is standard in modern UK houses for at least

30 years. Its a very common mistake for a newbie to remove all the wires from the fitting and then expect someone else to sort it out remotely. :-) Keeps happening to me with my relatives.

see

[news]

Thanks for your advice I will get in a electrician rather than kill myself, child, wife, etc (yes in that order). As despite the rather details explanations offered so graciously I still can't translate it into simple L N E on my simple wickes fitting! It is interesting to note that despite the fact that this arrangement is normal, fitments still come with overly simplfied instructions. Why can't the wires that decend from my ceiling match the f***ing diagram!

As a end note I know that as a complete amateur/dangerous electrician I sound completely thick but honestly if you ever need life support/haemodialysis/intropes I am your man!

Best Wishes

Chris

[news]

Dear Sugar Free

Your post made the most sense to me so I wondered if you could offer further info... Firstly all your comment are correct regarding stupidity etc. However having some previous disasters I am now extremely careful when it comes to 240v! Therefore looked at the instructions that came with the light fitting (yes it only talks about three cables LNE! it is a stupid assumption that Wickes would bother to full inform me about real wiring).

You mentioned that the cables came in three groups to three connections for a reason.

First group 3 all red and all live (Live feed IN, Live feed OUT, and Switched Live)

Second Group 2 all black and neutral (Neutral Feed IN and Neutral feed OUT)

Third Group 1 cable black and live (Switched LIVE) this should really be sheathed with red

How do I relate this to my L N E connections on my light fitting?

Many Thanks

Chris Essex (obviously)

[Dave]

Ignore this group. It is not needed for your light fitting. You will find a live else where. See below.

This is the neutral you need to feed to your new light fitting.

????

Are you saying that as a group you have a live and a black, or are you saying that you have a single core that is black and that it is a switched live? If the latter, then this is your live (switched) to your new light fitting. Connect this to the live on your new light fitting, but before you do, stick a bit of red tape on it.

To sum up.... Light fitting live is connected to the single black that should have a red sleeve on it. Light fitting neutral is wired to the 3 black cables. Earth is connected to the, presumably green and yellow sheathed cables that you have.

HTH

Dave

^^^^^^^

Why?

Do you wear white high heels and have blonde hair ;-)

[Bob Eager]

Hair coloured blonde...

[Dave]

Sorry, I forgot ;-)

Dave

[Lobster]

By way of explanation, the trouble is there are different ways of wiring lights; the first way is what you've got, using ceiling roses which have two or three stiff cables entering and leaving, plus usually a thin flex leading down to the actual bulb fitting.

The second way is using junction boxes, invisible *above* the ceiling... in this case, the same two or three cables enter the junction box, and instead of the thin flex leading to the bulb, you have another stiff cable leaving the junction box, and passing down through the ceiling (and which will also connect, indirectly, to the bulb). That is what you can see in the instructions. Electrically speaking, the connections inside the ceiling rose are just the same as in the junction box; and for almost any light fittings you buy in a shop, a junction-box wiring system is what you need. I think you're right to get an electrician in to sort it.

David

[Dave Plowman (News)]

Best thing to do is to buy a 3 plate ceiling rose - about 1.50 squids - and examine it. Far better than any explanation. And if this doesn't help you understand how they are wired, get a pro in. :-)

[Stefek Zaba]

As others have said - because there are different ways of wiring lighting circuits, all of which are legitimate and safe, it's hard to create comprehensive instructions which deal with all the common(ish) cases. It's also cheaper to manufacture 'universal' light-fittings which just accept the basic L,N,E needed to make them work, than to create national variants which integrate smoothly into the 'typical' ways lighting circuits are arranged in different countries.

There is, though, a way to keep things simple: but at the expense of it looking naff. How much the naffness matters is for you to decide. Leave in place the existing ceiling 'rose' - the thing with the three terminals you've mentioned (and the fourth one, where all the earth wires we hope you have meet up, which you haven't mentioned). Choose a new spot on the ceiling, close by, for your new fitting, and attach it - direct to the ceiling or to a new ceiling rose, depending on what it expects. Now run a short piece of 3-core flex from that fitting to the old rose. At the new fitting, connect the 3 cores to the 'obvious' terminals - brown to L, blue to N, green/yellow to E. In the old ceiling rose we're leaving in place - and haven't disconnected any of the fixed wiring from - connect (a) the green/yellow to the earth terminal, where all the sleeved-but-naturally-bare earth conductors are squished in; (b) the blue to the outer terminal where the two black conductors go (and where the blue wire of the old hanging lampholder flex was - and maybe still is connected); (c) the brown to the other outer terminal where the single black conductor is connected (and where the brown wire of the old lampholder flex was).

If that's either too nafflooking, or in the slightest bit unclear, stick to saving lives and track down a sparks willing to do a small quick job in Essex (good luck ;-)! If the naffness is marginal, you could do it 'for now' and get the sparks in once you've a couple more small electrickle jobs need doing, and get them to tidy this up as part of the slightly larger job (which it might be easier to get someone interested in).

HTH - Stefek

[chris French]

In message , news writes

Fair enough, though it's unlikely you'd kill anyone directly, though you may trip an MCB/blow a fuse.

The 'problem' you have come across is common with light fittings rather than just a ceiling rose. I do think it is a bit unhelpful to produce fittings without the necessary terminals for loop-in wiring, given that it is the standard way to wire lights in the UK. Let alone supply instructions which as you have found aren't going to be helpful, and possibly dangerous (presumably because they are sold in various countries)

What I do is either convert to a junction box in the ceiling space, or use some choc block connectors to take the connections that would go into the various terminals on a the ceiling rose, then connect the switched live connections to the 'live' and 'neutral' terminals on the fitting. If it has an Earth connection (if is metal it should), then connect that to earth.

[Christian McArdle]

If there are no green/yellow sheathed conductors, then the circuit has no earth available. If the light fitting has an earth connection (usually because it has exposed metal parts), then you can't fit it and should return it to the shop.

Christian.

[Sugar Free]

They call me that for a reason :-) Must be the "niceness" all taken out.

Those comments are for your safety - not my ego.

When you've done a job like this twenty years and more, you've seen enough in the way of "DIY" electrical work that comes close to "DIY" funeral services.

I've nothing at all against anyone having a go, only so long as they bother to understand what they're doing first.

You did the right thing in asking, rather than attempting without knowlege....

Yep - the wires do different things. If you put 'em all together, you'd get a bang, and probably, a shock.

Yes, the LIVE side of the switch - that is, the voltage going to the switch, returning to the fitting when the switch is ON.

Absolutely should be.

The three red wires (L-IN, L-OUT, L-SW) can go into a connector together, and effectively removed from your equation. A small junction box which you can "hide" back up in the ceiling would help here.

The TWO black wires - your neutrals - got to N on your fitting - again, put them into the little juntion box and run out a tail to connect into your fitting.

The SINGLE wire, which should be red, but is black, and should be sheathed red, but isn't, is the return from the switch. When the switch is turned on, this provides the feed to your fitting, and so it goes to L on your fitting. Again, put this into your junction box, sheath it, and run out a red tail into your fitting.

[news]

Sugar Free,

Understand now, thanks a lot mate!

Chris Blonde Essex