DIY Doctor

Advice needed please.

Postby coops9666 » Sun Jul 20, 2008 11:55 am

Hi Guys, need advice if possible.
Had one of my ceiling roses taken out by plasterers in the house and they did not write down the config of wires.
I have 3 wires, two mains and a switch i assume.
I have wired all combinations and now have all the lights working fine except the new rose which is stuck on constant on.
Anyone know what the problem is?
All advice appreciated
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Simply Build It

Postby ericmark » Mon Jul 21, 2008 1:23 am

I would guess you have connected the local lamp to the red/brown wire instead of black/blue wire with red/brown sleeve. Normally the switch wire is normal twin flex and the wire normally used for neutral has a sleeve on it and is used for the switched line wire.
Note red/brown is either red or brown according to age of wiring.

Postby coops9666 » Mon Jul 21, 2008 7:17 am

Thanks eric,
All three wires look exactly the same to me, black, red and earth.

I have the three reds wired to the centre of the rose and the earths accordingly leaving 3 black.
The blue flex has two spare and the brown has one has one spare.
So by labelling the 3 blacks A,B and C I can do all combos, ie A in the brown and B,C in the blue, then A, CB then B, AC etc etc.
The only combo that gets the final two lights in the run to work involves C in the brown and the other two in the blue, however this keeps the light constantly on, the other lights works fine with there switches.
The new light stays on, I have checked the switch and it is wired fine, red in common and black in L1.
Any ideas?
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Postby ericmark » Mon Jul 21, 2008 9:50 am

About to go out so in true Blue Peter style here is one I did earlier.
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.


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