2 way switch wiring problem


Postby Dunny007 » Mon Dec 17, 2007 7:46 pm

well i have a problem as i have recently had my kitchen re plastered and the plasterer remover the lights and taped the wires up i today have bought some new lights for this room. they work from a two way switch. the first light had 3 red 3 black and 3 earths easy i thought then i noticed a single black on its own not part of the row im presuming thats from or to the switch. The second light has 1 red and 1 earth itogether then again a single black on its own again i presume from or to the switch can get the lights on but when i press the switch off BANG there goes the fuse any ideas? im fresh out! Thank you
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Postby rflight » Tue Dec 18, 2007 7:19 am

Under Part P of the Building regs this work is notifable. You need to call a competant electrician
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Postby stevenc1603 » Tue Dec 18, 2007 2:05 pm

OK lets go with the one with lots of wires first of all.

How many cables can you see. From the sounds of it there will be 3 twin and earth cables. (One red, one black and one earth in each) I'm going to ignore the single black wire for now.

Firstly you need to work out how its switched. Take the switch off the wall and see what wires are connected. I would expect to see a single cable with the red wire in the com terminal and the black wire in the L1 or 1way terminal. The black wire should have a red sleeve on it but this is frequently not there.

If this is the case you next need to work out which of the three cables at the light are the correct ones. This is easier to do if you have a multimeter that can check continuity. With the supply off you test across each pair of wires until you find one that's a complete circuit. You must have the light switch in the on position for this to work.

Now you know black wire is the switch live. You should mark this with a bit red tape or sleeving so you don't loose it next time.

Now take all your reds and connect them together. This group should not be attached to the light.
Take the 2 black neutrals connect them together then connect them to the blue neutral on the light fitting.
Take the switched live and connect that to the brown live on the light fitting.
If the light fitting requires an earth, connect it to the earth's from the other cables.
Now turn the power back on and see if the light works.

It would be helpful to ascertain what the other black is. Perhaps it sends a switched live to another light somewhere, or even to an extractor fan?

At the moment it sounds like you have the switched live connected straight to neutral which is why its blowing fuses.

Once you have that one you should be able to sort out the other light.

From what I have gathered, this shouldn't be notifyable work as you are not adding to significantly modifying the circuit, although I may be wrong.
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Postby Dunny007 » Tue Dec 18, 2007 8:12 pm

Many thanks for your replies they have been very helpful. I have chosen to get a competent electrician to help me better safe then sorry this close to xmas anyway. Thanks again
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Postby rflight » Tue Dec 18, 2007 9:17 pm

It is a bit of a gray area as the definition of locations can vary a great deal. Not saying i agree with it fully steve but a kitchen is a special location.
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