Bad wiring on my part

I have been having a really bad time changing a florescent light fitting to a four bulb light fitting.

I disconnected the strip light and there were three wires - two for the circuit and one for the switch. I then tried to connect all three wires into the new light fitting, 3 black wires into neutral, 3 red wires into live and three earths into earth - it is a metal light fitting.

Fortunately I could not do this as the holes in the new light fitting where too small so I connected the three wires together in a junction box (black to black etc.) and then connected a fourth wire to them so that I had one single wire to connect to the light fitting.

Yes, I know what you are thinking, the switch has two lives which I realised after I had switched the power back on. Stupid me. The lights came on fine when the power was switched on but when I turned them off by the switch the fuse went in the fuse box.

I then wired them into the junction box in the same way a ceiling rose is wired, and the same way as the diagrams show on this website taking into account that the switch has two lives.

However, now the same thing happens still. When I flicked the switch to turn them on after the power was switched back on the circuit blew again.

The only difference my system has to most of the diagrams is that I have wired all of the earths together so that the three inlet earths are connected to the one outlet earth in my junction box.

Does anyone know why the fuse keeps blowing when the switch is pressed? a quick response would be very much appreciated.

at a rough guess, you've most likely confused which wire is the switch, verify with wire is the switch by use of a multimeter

One wire is grey 1 or 1.5 mm2 whilst the other two are white 2.5 mm2.

I really can't see that I have confused the switch wire. Could there be any other explanations.

Also, there is very little wattage on this circuit so I can't be overloading it.

Adam is right, you have confused the switch cable with either the feed in cable or the feed out cable.
With the power OFF, connect a meter across red and black of each cable in turn and operate the switch to discover which is the switch cable.
If you don't have a meter you could lash up a battery and bulb assembly.
There is no other possibility.

Thank you I will try that.

I was thinking of soemthing earlier.

The switch is a double switch (there are two switches together) The other switch controls a different light. Are these two separate or could wiring the two lives the wrong way round in the ceiling rose affect things.

I realise that they are both lives but is there a chance that wiring them the wrong way round could blow the circuit?

Mixing up the wiring at the switches is very very unlikely to blow the fuse, for that you would need to have both Live and Neutral at the switch.

pyoungson said:

One wire is grey 1 or 1.5 mm2 whilst the other two are white 2.5 mm2.

I really can't see that I have confused the switch wire. Could there be any other explanations.

Also, there is very little wattage on this circuit so I can't be overloading it.

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For reference, you can identify the switch cable when you have 3 cables at a light without a meter by carrying out the following:

1. Turn the power off

2. Connect all earths together.

3. With the light switch in the off position connected any two cables together red to red - black to black or if you have the new colours blue to blue - brown to brown.

4. Turn the power back on and check around the house to see if all other lights work. If they do then the spare cable is the switch cable. If they don't then turn the power off and repeat the above using the spare cable and one of the others.

5. Repeat the above until you have all the lights in the house working and one spare cable which will be the cable to the switch.

To make identification easy at second fix some sparks used grey 1.0mm for the switch wire and white 1.5mm for the feeds so that would be a good starting point when carrying out the above.