oops - nearly blew up the house darling!

[bobhope23]

Hi
Our landlord has recently renovated our flat, including removing the florescent light in the kitchen but neglecting to put the new light he bought as a replacement.
I got tired of cooking by candle light (usually undercooked than over) any how so I tired to put up the new light and oops big spark and no lights in the rest of the house.

Wisely I removed the lighting fuse, it was only when I put it back there was a spark at the fuse box.

so this is what I did,

basically there are two sets of main white cables protruding from the ceiling, from which there are one red(live), one black(neutral) and one yellow/green(earth) wire coming out of both of the cable.

the red wires coming out of both of the white cables are joined together by one of white plastic connectors with little screws in it.

and the yellow/ green ones are joined together by twisting.

the black cables are separate to each other and the naked end of the wire has been insulated with white insulation tape.


so I removed the little white connector from the two red cables and since they were both twisted together I connected them to the new light, to the connector position marked live, I joined the two black cables together and connected them to the new light to the connedctor marked N, and finally I connected the neutral cables together and fixed the new light to the ceiling.

When I put the lighting fuse back in, it made a loud pop and made me jump.

I don't understand what I did wrong,

please can someone advise me, it's the bank holiday weekend, and I'm sure someone can advise me what to do.

Before you ask, I haven't got a voltage meter.

thankyou.

Bob

 

[IanSF]

I would hazard a guess that you should have connected the light to the two black wires. One of the cables is the live feed from the consumer unit and the other is the wiring to the switch. One of the cables should have had the black marked, ideally with red tape, to indicate 'switched live' as it is the return from the switch. If you look at breezer's second diagram in this thread and compare your wiring with the last light fitting (marked dining room) you should see what I'm getting at.

 

[ban-all-sheds]

basically there are two sets of main white cables protruding from the ceiling, from which there are one red(live), one black(neutral) and one yellow/green(earth) wire coming out of both of the cable.

That was where you started to go wrong, when you assumed that both black wires were neutral. They aren't, one is a switched live, i.e. when the light switch is on, it becomes live. It should have been marked with a bit of red sleeving, but this is very commonly not done.

the yellow/ green ones are joined together by twisting.

That's bad - they should be properly joined with choc-block too.

the black cables are separate to each other and the naked end of the wire has been insulated with white insulation tape.

Both of them, or just one? If one, that might have been the switched live, but it's probably too late to tell now.

so I removed the little white connector from the two red cables and since they were both twisted together I connected them to the new light, to the connector position marked live, I joined the two black cables together and connected them to the new light to the connedctor marked N, and finally I connected the neutral cables together and fixed the new light to the ceiling.

I could see that coming....

When I put the lighting fuse back in, it made a loud pop and made me jump.

I don't understand what I did wrong,

When you connected the two blacks together you were creating a live-neutral short circuit.

Take a look at the For Reference topic, and read about lighting circuits.

Before you ask, I haven't got a voltage meter.

Sigh.

Do you have any form of voltage-indicating equipment, like a voltstick, or even an accursed neon screwdriver?

If not, I can tell you how to work out which wires are which with some choc-block and a pendant lampholder, but it'll take more faffing about.

 

[bobhope23]

Thankyou to Ian sf and ban all sheds for replying to my question.

Both of them, or just one? If one, that might have been the switched live, but it's probably too late to tell now.

Both of them had the white tape on it.

Do you have any form of voltage-indicating equipment, like a voltstick, or even an accursed neon screwdriver?

I don't afraid but I could go out and get a accursed neon screwdriver- are they expensive?

If not, I can tell you how to work out which wires are which with some choc-block and a pendant lampholder, but it'll take more faffing about.

that would be helpfull.

 

[bobhope23]

I had alook at this explanation having read Iansf reply, the only thing is in my example there are only 2 main cables in this diagram and example there are three cables one of which is going to the switch light.

This diagram, focuses on Breezers ceiling rose.

 

[IanSF]

This is the part of the diagram I was referring to. As breezer explains in his text, and in fact in your case, the switch cable is normal T&E.
What you need to do is to restore the wiring to how it was before you started and identify which of the two cables runs to the switch. I'm not going to try and pre-empt B-A-S, as he is qualified where I am not.

 

[bobhope23]

i've restored it to how it was, Unfortunately the decorator who removed the flourescent light just put white insulation tape onto the two black cables whithout differentiating between the two.

 

[plugwash]

connect the cables to the light one at a time (as the only cable connected)

one will make the light come on permanently (the cuircuit cable) the other will not make it light at all (the switch cable)

take care to appropriately terminate the cable that is not connected to the light while doing this

 

[TexMex]

I'd say the easiest way to get the thing working is.
Remove fuse
Fit one black into the left hand connector block.
both reds in the middle
The last black in the right hand connector block.

Connect the brown wire of the fitting to the middle block (permanent live)
Fit the blue wire of the fitting to one of the other connectors.
Refit fuse. check if light is on, and remove fuse again


If light didn't come on, take blue wire out and fit to other end.
(blue is now connected to permanent neutral)

Take brown wire out of centre block and connect to opposite end to the blue.
Refit fuse.

Oh, and of course, both earths should be connected to the earth terminal of the fitting (if it has one) or into a single chock block.

 

[ban-all-sheds]

My plan would have been the same as Plug's, but if you're refitting a rose rather than some other sort of fitting, TM's is a good one, as you're going to have to fit the rose anyway, so why not test the wiring from that.

FYI - the reason he suggested those steps, rather than just wire it up and connect the light to the two blacks (which would work fine) is that with some light fittings it matters which way round you connect live & neutral.

Anyway - good luck - let us know how it goes,

 

[bobhope23]

I gave plugwash's explanation a go and it still didn't work, this is what I did,

I connected one of the black wires(coming from the ceiling) to the cable marked live on the actual light, the other black cable I insulated.

The earth cables I connected to the earth of the actual light

the two red cables coming out of the two separate cables are joined together with a spearate connector block.

the connector block section marked neutral on the actual light was left disconnected.

replaced the fuse
turned on the switch and it didn't work
so
I reversed it and used the other black wire and connected it to the cable marked live on the actual light and replaced the fuse and still didn't work.

 

[dingbat]

"the connector block section marked neutral on the actual light was left disconnected."

That's why it didn't work!

Think of it this way; the reds are just joined together and not connected to anything else. The earths are joined together and connected to the earth terminal of the light. That leaves you with two black wires. One of these is the neutral and the other is the switched live. Unless you have screw-in type bulbs (Edison Screw, or 'ES') it doesn't matter which way you connect to the live and neutral of the light.

If you do have screw-in bulbs it will still work with them connected either way, but is potentially more dangerous depending on the construction of the lampholder.

 

[bobhope23]

I connected up both the black cables, one to the live and neutral and looks like I got it right first time, put the fuse back in and it the light worked.

Thankyou for your help, when your working with something like electrics which I am completely in the dark about, forums like these can be your saviour.

I really do try to work things out for myself, but with electrics you really do have to ask the advise of people who know what they are doing.

Everytime I came to put the fuse back in, I was abit nervous. thankfully I might not have to do that for a while,

wish everyone a pleasant weekend.

bob hope