Acceptable to run under-pelmet kitchen flourescent from the

misternomer

Hi all,

I got myself in a bit of a mess when I moved into my current house. We have wall sockets flush mounted into the splash-backs in the kitchen. Above these we obviously have wall units under which I wanted to mount a long strip light with a switch right next to it.

I removed tiles above mains socket, chased a length of twin and earth in and connected a switch right next to the light .. and on to the light.

Switched the supply back on and basked in the glow of my new lighting. Then hit the switch to turn it off and the switch blew, also shorting the RCD at the consumer unit.

There are so many ways to call me an idiot. Try to be imaginitive:-)

Obviously taken a wrong turn with my wiring. Any pointers? Want to see a photo?

Help would be very much appreciated.

electronicsuk · Posted: Wed Sep 12, 2007 1:52 pm Post Subject:

Yes, a picture would be good. I also hope you haven't taken the supply directly from the back of a 13A socket through a standard unfused light switch. Sounds like you wired it between L+N, turning the switch on caused a direct short but the lights were quite happy running with the switch open.

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Matthew

"I told you, I only wrote that poem to test my printer!"

misternomer · Posted: Wed Sep 12, 2007 1:58 pm Post Subject:

Yes - you've got it in one there. I took the supply direct from the back of a 13A.

What would be the correct procedure? I don't mind using a switched fuse as the lighting switch but need guidance on wiring and specification. e.g. connect the red wire to the L1 and the blue wire to L3 sort of stuff.

Pics on their way this evening.

electronicsuk · Posted: Thu Sep 13, 2007 5:55 am Post Subject:

Assuming there is no possibility of taking a feed from the lighting circuit for whatever reason, I would spur off the nearby socket (but it MUST be part of the ring) with 2.5mmsq T+E and feed into the supply side of a switched Fused Connection Unit. I would then run 1.5mm T+E from the load side of the FCU to the light fitting.

You need to read the WIKI and make yourself aware of the safe zones and how (and not) to run cables behind plaster. If you don't know the difference between the terminals on switches and FCUs then I'd be concerned this job is a little outside your scope, but if you feel you must DIY then all the info you want is in the WIKI.

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Matthew

"I told you, I only wrote that poem to test my printer!"

Space cat · Posted: Thu Sep 13, 2007 7:32 am Post Subject:

It's a classic boo boo. You've wired your switch and light in parallel instead of seres. My father did it once - and him a science teacher too! Draw yourself a little circuit diagram and, hopefully, you'll spot the mistake.

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Taylortwocities · Posted: Thu Sep 13, 2007 7:19 pm Post Subject:

But please do post a picture, We love pictures!

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Albert · Posted: Thu Sep 13, 2007 7:38 pm Post Subject:

1) Make the fused spur part of the ring.
2) As mentioned use 2.5mm2 cable.
3) If you are using 1.5mm2 (which will be ok for this job) to connect from the fused spur load side, DO NOT FORGET TO CHANGE THE FUSE IN THE SPUR TO 5A!.
4) If you do not want to use the spur as the switch, you can add a light switch between the spur and the light.
5) If you are not sure how to connect the switch, don't do it, call some one qualified or use the spur.
6) Do not forget to turn off the MCB before you touch the circuit.
7)it might be that the light fitting is class 2 (no earth required), if so do not cut back the earth wire just insulate it safely.

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misternomer · Posted: Mon Sep 17, 2007 9:26 am Post Subject:

Guys,

Sorry for the slight delay in getting back to you. Little one has been poorly all weekend so time stood still.

Below are a couple of images of the offending mains socket. It should be fairly clear to see what I've done so far. No taking the p*ss out of my grouting:-). I understand what you're saying here. Don't shove the new piece of twin and earth into the mains L&N terminals along with the existiing (N)black and (L)red cables. That would be a parallel circuit which means that closing the switch would result in a direct short:-) Instead I need to connect in series....could somebody please clarify exactly how to do this. I know what is meant by a serial connection - but for the avo8idance of doubt.

I'm very happy to use the switched FCU as the light switch itself. In the kitchen at the old house we just nfelt underneath the pelmet for the switch whenever we needed additional lighting for food prep.

Obviously your warnings about MCB safety etc are heeded.

[img]

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electronicsuk · Posted: Mon Sep 17, 2007 2:21 pm Post Subject:

Ok, a few tips here. First off, you really have a few too many cables going into that socket. It looks to already be part of the ring with a spur, and I would advise against taking another spur off it.

Second, get some earth sleeving to put over that bare copper CPC!

Third, what you need to do is take L, N and E from a socket (preferably not this one) in 2.5mmsq and bring it to a switched FCU. This will have L and N supply connections, L and N load connections, and a couple of earth terminals.

At the FCU you should bring all your earths together from the 2.5mm supply and 1.5mm load cables, it doesn't matter which earth terminals you use (there are normally two on an FCU) as they are all interconnected. Wire the 2.5mm from the socket into the corresponding L and N supply terminals on the FCU. Wire the L and N of your 1.5mmsq cable to the corresponding L and N load terminals, and take the other end to your light fitting. Fit a 3A fuse in the FCU, remember your earth sleeving, and the rest should be self explanatory.

If you don't want to use the FCU as a switch then you need to insert a single gang light switch somewhere along the run of 1.5mmsq. To do so, you'll need to cut the cable, feed the incoming live to common of the switch, outgoing live to L1, and use two terminal blocks to join both earth and both neutral cores.

__________________
Matthew

"I told you, I only wrote that poem to test my printer!"

aptsys · Posted: Mon Sep 17, 2007 2:37 pm Post Subject:

Make sure you only use 2.5mm when spurring off a ring main. It looks like you've used 1mm along with spurring off a socket that's already spurring something else

misternomer · Posted: Mon Sep 17, 2007 2:59 pm Post Subject:

Sounds clear but I must be missing something. If I'm taking all of my LN and E's from the mains socket and up to the FCU via 2.5mm sq, then how am I feeding the circuit back to the mains socket...having just removed the LN&E from the mains socket?

In your explanation I'm not leaving any of the existing wires in situ on the mains socket - right? Surely I need to feed the circuit ba.ck in to the mains socket via the FCU?

Warnings about spurring off a spur and using a 2.5mm sq are heeded.

electronicsuk · Posted: Mon Sep 17, 2007 3:54 pm Post Subject:

No, no, no... I'm not suggesting you remove all the wires from that socket. Rather, you spur from it using a length of 2.5mmsq (as you have already done) to feed the FCU.

Now we know the socket already has a spur running from it this changes things a little, is it too late for you to take a feed from an alternative socket?

__________________
Matthew

"I told you, I only wrote that poem to test my printer!"

misternomer · Posted: Mon Sep 17, 2007 4:25 pm Post Subject:

To be honest I'm loathe to start taking more tile off the wall only to find that there's yet another spur in the next one.

So I'm leaving the existing wires in the mains socket and simply doing the following:

At the socket:
Blue into neutral contact
Brown into live contact

At the FCU
same as above

Taylortwocities · Posted: Mon Sep 17, 2007 4:53 pm Post Subject:

Those thin wires in the back of the socket (1mm² ?) should not be there and must be removed.

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When you get to the end of your rope, tie a knot and hang on. - F.D.R.

misternomer · Posted: Mon Sep 17, 2007 5:03 pm Post Subject:

Ok - so if I take the tiles off, remove the 1mm2 from the wall and put a length of 2.5mm2 in instead it should be fine as per my above?