Problem with light fitting


Postby slick67 » Sun Apr 26, 2009 8:04 pm

I am trying to fit a new light fitting but can't seem to get it to work.

The light in question is the main ceiling light, it has the usual 3 grey cables with red, black and green wires plus a 4th grey cable with a red core. The light can be operated from either of 2 switches, one downstairs and the other one upstairs.

Can someone please advise me on where each wire should go as I think I must have one or more of them in the wrong place.
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Postby bd3cc » Fri May 01, 2009 9:10 pm

What cables doyou have at he switches? Ignore the green earth for the moent?
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Postby slick67 » Sun May 03, 2009 1:22 pm

Downstairs switch just has a red and a black wire. Upstairs switch has a red and a black wire plus what looks like the other end of the grey cable with the red core.
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Postby rosebery » Sun May 03, 2009 4:05 pm

First of all it might be good to know what country you are in slick?

'Cos if its UK and you have "normal" red, black and green cores then its possible you should be thinking about a rewire. This cable is old!

Cheers
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Postby slick67 » Mon May 04, 2009 7:58 am

I am in the UK, a rewire is a bit of an expensive option at the moment, I just need to get the landing light working again.

I'm guessing that the problem is where should the 4th grey cable with the red core go.
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Postby bd3cc » Mon May 04, 2009 10:43 pm

Sorry to disagree, Rosebery, but this cable was in use unti at least 2005, when the insulatin colours were changed, and if it is solid core, rather than stranded, it should be good for 30 yrs from installation.

That was an aside and didn't help the poster.
If the light is a proper 2way ( can be switched on/off from either of 2 switches, there must be at least 3 single cores at each switch.
As you say there are only 2 at one switch, i suspect this was a 1 way, which has been converted to be a 2 way but will only work as a 2 way if the swtch with 2 cores is on.

Try the following:
red single to COM
red of pair to L1
black of pair to L2

at the other switch
red of pair to COM
black of pair to L1

You can play around with the combinations as it does not matter, you will not blow anything., it will either work or not. That is what a sparky would do.
It does help however if yo can identify the live wire coming into one of the 2 switches
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Postby rosebery » Tue May 05, 2009 6:03 pm

Sorry to disagree, Rosebery, but this cable was in use unti at least 2005, when the insulatin colours were changed, and if it is solid core, rather than stranded, it should be good for 30 yrs from installation."

He's got a green insulated earth wire rather than a green/yellow sleeved CPC unless I read it incorrectly. If that was in use up to 2005 I stand corrected.

Cheers
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Postby rosebery » Sun May 10, 2009 6:44 am

@ bd3cc

I wrote:

"He's got a green insulated earth wire rather than a green/yellow sleeved CPC unless I read it incorrectly. If that was in use up to 2005 I stand corrected."

in response to you. Could we clear this one up please?

Cheers
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Postby bd3cc » Sun May 10, 2009 11:43 pm

Agree that green insulated earth was not in use in 2005 and cannot,from memory date the change to green/yellow, but red/black phase cores were, which is what i was suggesting.
from the posters point of view, one can ignore the earths as they are common, and their problem is where to put the phase conductors to get their system working.
Pett quibles over whether earth should be green or green/yellow do not help them, because as we both Know you can come across both and still know what it is.
Regards
bd3cc
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Postby slick67 » Sat May 16, 2009 9:33 am

Fixed now.

Thanks for your help.
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Postby rosebery » Sat May 16, 2009 9:59 am

"Agree that green insulated earth was not in use in 2005 and cannot,from memory date the change to green/yellow, but red/black phase cores were, which is what i was suggesting.
from the posters point of view,"

No you weren't you were suggesting that very old style red, black and green insulated conductors were in use in UK until 2005 - hence my question to you.


"one can ignore the earths as they are common, and their problem is where to put the phase conductors to get their system working."

Yes unless the cable is that old that its potentially downright dangerous when its disturbed in which case any the advice should be "leave it alone until an electrician looks at it" irrespective of whether the lights are working or not.


"Pett quibles over whether earth should be green or green/yellow do not help them, because as we both Know you can come across both and still know what it is."

You miss the point that we frequently get posters here from overseas who ask seemingly inocent questions to which they get a UK based answer which could be quite wrong in their own country - hence my question to the OP. Thats not quibbling - thats being responsible.

Cheers
Last edited by rosebery on Sat May 16, 2009 3:05 pm, edited 1 time in total.
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Postby slick67 » Sat May 16, 2009 1:04 pm

Just when you think you've fixed one problem it creates another one. :roll:

Now when you switch on the light it cuts the power supply thru to the burglar alarm which is the next appliance in the loop, although everything else upstairs still works.

This is how I've wired it up:-

Line - the single red plus one black
Loop - the other 3 reds
Neutral - the other 2 blacks

Any ideas?
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Postby bd3cc » Sun May 17, 2009 9:17 pm

I would suggest that the alarm should have a permanent live and neutral feed, normally installers do not like to have their system connected to any other system.
you need to find which cable (red/ black +E) feeds the alarm. The red should then be in the loop, and the neutral in the common neutral terminal.
Try identifying the alarm cable and disconnect, re-instate the normal 3plate system so that all lights operate as they should, then do the above with the alarm.
You will need a continuity tester to do this.
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