I've tried changing the lighting in a room and I found a set of wires that I don't know to to connect in order to have a live, neutral and earth. Can anyone explain?
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What is this a picture of? Is this behind a light switch, or one of the lights?– Fredric ShopeNov 21 at 14:39
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Behind the lights– AndreeaNov 21 at 14:43
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Will the new fixture fix to the ceiling if you leave the original rose in place [the bit that has all the wires out of the ceiling, not the cover necessarily. If not, we need to see a picture of what is going to replace it. Don't take the existing rose/wiring apart until you know what to do with the wires. You'll lose track of what is what.– TetsujinNov 21 at 18:58
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BTW, this is really important, because whoever wired that in the first place used completely the wrong cables, so the colours are lying to you.– TetsujinNov 21 at 19:07
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3 Answers
Firstly, note that the three groups of wires are effectively bundled by their respective brass contact sets (buses) and kept in isolation.
Based on my understanding of U.K. wiring convention...
- Red is hot (live). Likely one comes in and two go out to switches and other circuit branches. In your case, the red next to the yellow may be outbound to the switch.
- Blue is neutral. It appears connected to black neutrals, which are common in older wiring.
- Yellow is probably the return hot from the switch.
- Yellow/green is ground (earth). The existing light doesn't appear to be grounded. This is common as many fixtures are "double insulated" and don't require ground. If your new fixture has a ground wire it should be connected to that screw.
Therefore, by connecting a new light fixture as this one is, you'll have neutral to neutral and hot to switched hot.
You'd be wise to own and use a multimeter to confirm all this.
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In order to change the light fitting we need to remove the existing brass contact sets. The white plastic behind it won't fit with the new fitting.– AndreeaNov 21 at 17:43
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Ok. And? Is there a question in there? If reconnecting those wires in the same configuration with new connectors is challenging you may not be qualified for this task. Nov 21 at 17:44
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Of course I'm not qualified. My husband changed all the light fittings in the house but this look a little too complicated. I thought someone will be able to help– AndreeaNov 21 at 17:47
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1The new fixture is ready to take the place of only the drop to blue & brown from your old fixture [plus a new jumper earth you'll have to make up.] The wiring in the ceiling is a confusion of 'wrong colours' you do not want to mess with. You cannot be certain which is which from the colours alone, only by their positions in the old rose/bus bar.– TetsujinNov 21 at 19:04
Your old fitting is a standard UK ceiling rose with connector groups for earth, neutral, loop (live in), and light (switched live). Your new fitting has only got three terminals: live, earth, and neutral. In order to replace the rose with the new fitting, you MUST fit a new junction box above the ceiling.
It looks like you have 3 cables coming into that rose. 2 are 2-core+earth (read and black). These will be power in (from the consumer unit) and out (to other fittings on the same circuit). There is also a 3-core+earth cable (red, blue, yellow). This will be the switch cable.
You will need a new piece of 2-core+earth to go from the new junction box to the new fitting. This will have brown and blue wires in it.
In the junction box, the connections are as follows:
- All bare wires (earth)
- All 3 red wires (live)
- both black wires and both blue wires
- yellow wire and brown wire
In the light fitting, the new brown connects to the L terminal, the new blue to N, and the bare to the earth symbol.
The 5A lighting junction boxes can be difficult to use properly. It is very easy to lose the terminal screws or to fit them badly and damage the terminals. If you are at all nervous about this, get a professional in.
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I'm confused. Why is a new box warranted. It seems like this "rose" is mounted to a box, which may well be suitable. No? Nov 22 at 14:12
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1The rose is the section currently mounted to the ceiling. This has a cover that screws on. The new fitting has no threads to screw onto the existing rose, and is unlikely to be the same size. The new fitting has a pair of slots which hook over screws on a bracket that needs to be fitted in place of the existing rose. Having worked with that general sort of fitting before tells me that the bracket will not have any terminals for cables. hence the need to introduce a new junction bx for the switch loop.– rhellenNov 23 at 13:20
The ground (middle) terminal on the new light should be connected to the spare ground terminal on the left side of the ceiling box with a new piece of yellow/green wire.
Disconnect the brown and blue wires from the old fixture in your hand. If they are not removable, cut them as close to the old fixture as possible. Connect them to the empty terminals on the new one. Brown to L and blue to N.
Pay attention to the routing of the blue and ground wires through the strain relief studs. Do that.
But.
The old fixture looks like it's threaded and screws onto the ceiling rose. The new one looks like it wants a couple of screws sticking out the sides to hang on. I'm not sure what the solution is to that. You may have to replace the whole ceiling rose. Probably a job for an electrician if you're not comfortable with it. Start by taking the light to an electrical supply store and buying an appropriate ceiling attachment.
