I've somehow broken a circuit...help

[Cagn]

Hi everyone. Love the forum here, but I can't find an answer to my problem.

I have taken downt the light in the kitchen to replace it with another. When I took it down I noticed there were three sets of leads. I made the mistake of putting all the reds together and all the blacks together.....and I blew a fuse
So I came across this website to see what to do. I have done exactly this:

http://www.diynot.com/wiki/electrics:lighting:problems:blackswlive

But none of the lights on the circuit work. I've replaced the fuse and tested all the others.....what am I doing wrong? Where else should I look for a fault?

Hope you can help

 

[Lectrician]

Are you sure you changed the right fuse? Was it a rewireable? Have you repaired it without snapping the replacement wire?

Is this fuse part of your main fuse board, or is there others?

 

[Cagn]

Hi Lectrician, thanks for the reply.

I have replaced the fuse in the fuse box, and I've tested all the others in the box, so I'm sure there is nothing wrong there. There is only the one fuse box.

I've also replaced the bulbs to see if they had blown. Still nothing.

One thing.....I haven't wired in the replacement light yet. Just trying to get the others working first. But that wouldn't make any difference would it?

I'm confused

 

[riveralt]

Lighting circuits are radial in design - which means they go from the consumer unit (fuse box) to the first ceiling rose then to the second etc.
If the live and/or neutral loops are broken then any of the lights after the break will not work.
It is possible that your light is the first on the radial circuit and there is a problem with either the way you have re-wired this light or with the wiring inside the consumer unit.
Three questions - I assume since you mentioned a fuse you have replaced the fuse wire in the this fuse and that fuse wire is properly connected to the terminals and still intact.
Secondly, if the fuse wire is in place and correctly terminated then you are going to need access to a multi-meter and know how to use it to progress any further.
Finally, how do you know that you have wired the circuit back correctly, where you able to identify the switched live and if so how?

 

[PrenticeBoyofDerry]

Do you have anything that can safely detect voltage? or continuity?
As you need to identify the switch live, which normally would be a black that should have been marked to identify it as that.
The three reds would normally form your live loop, two of the blacks then are neutral with the third black being switch live.
If you isolate the circuit:
You could id the switch live by terminating all reds together then having each black terminated in to a connection block separately.
Then energise:
Then test each black to earth for voltage this a live test, so be cautious of this. The one that shows a voltage of about 230V +/-, will be switch live.

 

[riveralt]

As you need to identify the switch live, which normally would be a black that should have been marked to identify it as that.
The three reds would normally form your live loop, two of the blacks then are neutral with the third black being switch live.

The OP has stated that he has set up and tested the wiring as per this:
http://www.diynot.com/wiki/electrics:lighting:problems:blackswlive
My question was how he did this without some form of test equipment?
Given the lack of any lights on the circuit if this isn't the first on the radial then its back to the CU and the fuse wire - is it properly terminated?

 

[PrenticeBoyofDerry]

The OP has stated that he has set up and tested the wiring as per this:

My question was how he did this without some form of test equipment?
Given the lack of any lights on the circuit if this isn't the first on the radial

Which is a fair question to ask.

then its back to the CU and the fuse wire - is it properly terminated?

Or trapped insulation or cable out of terminal.

 

[SimonH2]

You could id the switch live by terminating all reds together then having each black terminated in to a connection block separately.
Then energise:
Then test each black to earth for voltage this a live test, so be cautious of this. The one that shows a voltage of about 230V +/-, will be switch live.

Or it's the neutral from the rest of the circuit ("downstream" lights) and there's at least one light switched on. With a multimeter you won't see any practical difference in voltage - that would only show with a tester that imposed a significant load on whatever it was testing.

Far better to turn off all power - at the main switch if necessary to be certain it's off. Then you can see which black wire is a dead short to L with the light switch on, and open circuit with the switch off.

There is another way that uses the lights themselves as test gear.
Disconnect the black wire from the switch and terminate it safely (eg in a single terminal block). Connect all three black wires together at the rose (and all 3 red wires together). Now check that the rest of the lights on the circuit work - they should.
Now turn the power off, drop one black wire out of the terminal and put it in it's own terminal - ie so that you have 2 black wires joined and a third not connected to anything. Power back on, see if rest of lights work - if not you've got the wrong black, power off and try a different one. If that doesn't work, then try the third - and unless something is badly wrong then that must be "the one".
Mark the "spare" black wire with brown sleeving (or tape in a pinch - better than nothing). Put it in the switched live terminal of the rose, reconnect the black wire at the switch (it too should be marked with brown sleeving). Everything should now work.

 

[securespark]

Get a multimeter and make certain your fuse has continuity.

It is ever so easy to snap the wire when tightening the screws, but it looks intact.