Problem with wiring during light replacement


Postby sdm » Tue Nov 20, 2007 11:43 am

I tried to replace two lights in my living room yesterday, one was successful but the other one wasn't, here's an explanation.

My living room had three dome type lights in the ceiling, two down one end of the room and one at the other end.

I bought two lights with a rose and 5 spirals coming off it, each with a 40 watt bulb.

At the end of the room where there are the two lights, i removed one of the dome lights and was left with three wires, black, red and green. I wired this one up no problem and fixed it top the ceiling, job done.

At the other end of the room where there is a single dome light, i removed this one and was going to put the other spiral light there. This is where the problem started, when i removed the original light i was left with two sets of wires coming from the ceiling. There is two sets of black, red and green, although the greens are sleeved into one casing the blacks and reds are separate.

I have tried wiring the two reds opposite the browns (on the new light) into a four way connector block, the blacks opposite the blues (on the new light) and the green opposite the earth in the block.

When it switch the mains back on, the fuse that is for the lighting blows every time. The fuse at the main box for the lighting is 5 amp, is this too low for the new lights?

Thanks for your time.

sdm
sdm
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Joined: Tue Nov 20, 2007 11:29 am

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Postby stevenc1603 » Tue Nov 20, 2007 2:53 pm

Sounds like this light is on the end of the circuit, seen as it only has 2 cables.

Keep the 2 red together but don't connect them to anything on the new light.

Of the 2 blacks one will be the neutral and the other will be the switched live and should technically have a red tag or sleeve on it, although it frequently doesn't

You'll need to try and figure out which cable is the source from the circuit and which cable is the switch. There are a couple of different ways of doing it.

Once you have which black is the neutral and which is the switch live connect the neutral to the blue wires of the light and the switch live to the brown of the light.

Above all be safe and don't fry yourself!
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Postby sdm » Tue Nov 20, 2007 4:34 pm

Thanks for the reply.

That's what i haven't tried.

It's a but strange that the two blacks are not marked at all, how unhelpful is that.

Will it mean that the fuse will blow again if i get them the wrong way around, or is it hard to tell.

Thanks,

sdm
sdm
Posts: 3
Joined: Tue Nov 20, 2007 11:29 am


Postby stevenc1603 » Tue Nov 20, 2007 11:59 pm

because its just a light it probably won't blow. If it were a motor it would run backwards. You really should identify the correct wires.

One way to do it would be to separate the 2 reds and wire one red to the live of the light and the black from the same cable to the neutral for the light.

Make sure the other wires in the other cable are safely insulated.

Stick the fuse back in. If the light comes on you have the live and neutral of the circuit, and the other cable is the switch cable. If it doesn't turn on then you have the switch cable connected and the circuit one disconnected.

Either way you should be able to identify the correct black that should be tagged.

Put the reds back together and wire the black and blue neutrals together then wire the now tagged black to the live of the light and it should all work fine.

If you have had the 2 blacks together it will blow the fuse as your shorting live straight to neutral.

HTH
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Postby sdm » Wed Nov 21, 2007 8:56 am

Thanks you for the advice.

It certainly is clearer than it was before.

I'm not going to get the chance to do this before the weekend but am confident now that i can sort the issue out.

Thanks,

sdm

p.s. I'll post back and let you know
sdm
Posts: 3
Joined: Tue Nov 20, 2007 11:29 am


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