Light Fitting - 2 Wires or 3?

edmund_blackadder

Hi,

I hope you can help me. I have searched this forum and there appear to be quite a few threads about people changing light fittings.

Unfortunately I committed the cardinal sin of taking down the old light fitting without making note of which wire goes where.:doh:

I can see 2 cables (not 3 as I believe is usual) each with the red, black and neutral wires. The thing I'm not sure about is should there be 3 cables (i.e has one disappeared up into the ceiling?) or is 2 fine? I have some vague understanding that it is possible to have a situation where the light would work with only 2 cables? Unfortunately accessing the space between upstairs floor and downstairs ceiling is not an option so I can't check from above.

Are there any checks that I can do to tell if there should only be 2 cables?

(sorry of this doesn't make sense!)

andrew-b

If there's two cables then one is the switch cable and one the live feed (likely from another ceiling rose).

See http://www.ultimatehandyman.co.uk/diy/electrics/light_fitting/ceiling_rose_wiring.htm

BTW ...red = live, black = NEUTRAL, copper sleeved in green/yellow = EARTH.... sounds to me like you may have read a recent post by aliasojo who recently referred to earth erroneously as neutral! Be careful reading other peoples posts on electrics - one of the reason i limit my advice in these threads now!

Andy

edmund_blackadder

andrew-b wrote: »

If there's two cables then one is the switch cable and one the live feed (likely from another ceiling rose).

See http://www.ultimatehandyman.co.uk/diy/electrics/light_fitting/ceiling_rose_wiring.htm

BTW ...red = live, black = NEUTRAL, copper sleeved in green/yellow = EARTH.... sounds to me like you may have read a recent post by aliasojo who recently referred to earth erroneously as neutral! Be careful reading other peoples posts on electrics - one of the reason i limit my advice in these threads now!

Andy

Whoops ... yes I do know that the green/yellow one is Earth ... I absent mindedly posted 'neutral'! D'oh!

Is there anyway I can guarantee that there should only be 2 (without pulling up floor boards)?

Locknut

there can be only 2 if it is old wiring but if your not sure what wires you have call in a professional, it's cheaper than setting your house alight or worse a funeral!

27col

If there are only two cables, it is likely that the light fitting is at the end of the loop. In this situation is normal for there to be only two cables. The easiest way to find out if there is a cable missing is just to separate all the cores. Switch on the the power, and if all the lights work except for the light in the room where the fitting is being replaced, then there are only two cables. If some of the lights in the other rooms do not work, then this is because there is a cable missing which should feed to lights further along the circuit. It is very unlikely that a cable would spring up and disappear into the ceiling.

totalsolutions

end of the loop = end of run

edmund_blackadder

Thanks.

The instructions expect there to be 3 cables and expect you to match up 2 of the reds and 2 of the blacks. Since I'm dealing with the end of the loop do I just wire it up the same (but without the extra wires)?

fto

Just put the 2 reds in a connector togeather, then put one black to the neutral on the fitting & the other black to the live on the fitting ( does not really matter which way round they are).

vaio

27col wrote: »

If there are only two cables, it is likely that the light fitting is at the end of the loop. In this situation is normal for there to be only two cables. The easiest way to find out if there is a cable missing is just to separate all the cores. Switch on the the power, and if all the lights work except for the light in the room where the fitting is being replaced, then there are only two cables. If some of the lights in the other rooms do not work, then this is because there is a cable missing which should feed to lights further along the circuit. It is very unlikely that a cable would spring up and disappear into the ceiling.

On the other hand if the lights are wired as a ring then everything else would work even if there was a third wire still in the ceiling (which would of course be live with all the entertaining bangs, flashes & flames that could produce)

vaio

fto wrote: »

Just put the 2 reds in a connector togeather, then put one black to the neutral on the fitting & the other black to the live on the fitting ( does not really matter which way round they are).

Unless it has ES bulbs

edmund_blackadder

fto wrote: »

Just put the 2 reds in a connector togeather, then put one black to the neutral on the fitting & the other black to the live on the fitting ( does not really matter which way round they are).

Thanks .... that worked a treat!! :T:j