Help lighting, 3 red 3 black 3 nutral

Postby tinknpete » Mon Dec 31, 2007 1:25 pm

I know the 3 green netrral go to its own terminal as thus is where they were before.
Silly me did not mark the others when I took down the ceiling rose and cant work out where others go.
The wires are marked loop out loop in and rw, each has a red and a black, does anyone have any ideas.
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Postby sparx » Mon Dec 31, 2007 6:21 pm

Hi. first the 3 greens are earths NOT neutrals, don't let anyone tell you that is the same thing 'cause it ain't!. they go to the earth term. of the light if it has one or to a spare block if an insulated fitting is used.
You are fortunate the cables are marked, it's not often so.
The critical one is the one markes sw (Not rw), this is the switch cable, the black of it should be marked with red sleeving or tape to identify it as the sw/line coming back to the light and is a Live, not Neutral. This core goes to the Live term of light, prob. a brown flex.
the 2 other black (Neutrals) go to the other term of the light prob. a blue flex.
the 3 reds go together in a spare term block not connected to the light, and are L-in, L-out to next light & L-to switch, this is all drawn out in glorious technicolour under Doc's 'Projects' section,
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Postby ericmark » Mon Dec 31, 2007 6:45 pm

Regular question:- How does one wire a ceiling rose? The switch wires should be both red or at least have a red sleeve but in practice this is rarely the case. This is how to work out which black/Blue wire is which when all three cables are the same colours. These are:- The feed, The Switch, The next Lamp. Easy way is meter or buzzer across the cables with power all off and flick light switch until switch wire is found but often the DIY man has no meter or buzzer so next method.
Do not use energy saving bulbs as we need to be able to see bulbs working on half power use normal bulbs only. Do not use this method if you have dimmers or discharge lamps in any of the house lights.
1. With power off connect all cables except for neutrals and switch cable i.e. the black or blue are left disconnected. Put one into spare block connecter and other two in the two outer connectors of the ceiling rose i.e. one to each wire feeding lamp. Now turn on power and try if it works jump to 4. If not turn off power.
2. Swap either of two blacks (or blues) connected with one in spare block connecter and then turn on power again. If it works then jump to 4. If not turn off power.
3. Swap the wire in spare block connector with other black (or blue) in ceiling rose. It should now work one switched on again. If not there is another fault not at rose and it is beyond this simple check.
4. Turn off power again and mark cable in spare block connector with black or blue type or some other way to find it again. Then put it in spare hole with other Black (or blue) then turn on power.
5. Test all lights if all work OK then all is done on the other hand you may find odd things happening like with light you have been working on being switched on other lights don’t work and with it off the other lights work as glow only and light you were working on will also start to glow. If this is the case switch off power and swap the two unmarked black (or blue) wires. Now all should work.
So what are we doing? Well we can’t connect any of the three blacks (or blue) together as one is live when switched on so to start with we find out which wire connects to the next rose in circuit by time 1, 2, and 3 have been completed we know this is wire is spare block connector. At this point, we don’t know which of the other two blacks (or blue) is neutral and which is the switch wire. But if we connect the next lamp in series to switch instead of neutral it will do no harm but the next lamp can only get a return through the lamp in the light we have been working on so either the one we were working on will come on dim or the next in line will come on dim which is all to do with what size bulbs are fitted. But we now know exactly which two wires are the wrong way around. So finally we have in the eight holes in rose (earths normally under clamp screw) Feed to lamp, Feed from switch, break, Three live wires at all times all red or brown (one feed, one out to switch and one to next lamp), break, Neutral (in or out), Neutral (out or in), Neutral to lamp.
I hope this helps it was in proper blue peter style one I did early.

All best Eric

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