Wiring a loft light. Blows fuse

t3rm3y

I ran a cable from an upstairs light accessible from loft. I assumed the switched line connected was going to the 2screw connectors on the ceiling rose. I picked a brown wire from the central 3 connectors. Wired brown to this and blue to the same cables corresponding blue(neutral).
Connected cable to new switch. Wired up lamp. Turned fuses on and light came on(possibly left in on position) tested by switching it off and it blew the fuse.
Not sure what's wrong. Only thing was the earth didn't have any sleeve over it as can't find it.would that cause short of touched one of metal connections in switch?
Or is it the cable I piggybacked off in ceiling rose ?

pramsay13

If you're asking these questions I think it's maybe time to call an electrician.
There shouldn't be any assuming when you're dealing with electrics.

Risteard

t3rm3y wrote: »

I ran a cable from an upstairs light accessible from loft. I assumed the switched line connected was going to the 2screw connectors on the ceiling rose. I picked a brown wire from the central 3 connectors. Wired brown to this and blue to the same cables corresponding blue(neutral).
Connected cable to new switch. Wired up lamp. Turned fuses on and light came on(possibly left in on position) tested by switching it off and it blew the fuse.
Not sure what's wrong. Only thing was the earth didn't have any sleeve over it as can't find it.would that cause short of touched one of metal connections in switch?
Or is it the cable I piggybacked off in ceiling rose ?

You are clearly wholly incompetent to be carrying out this work and have created a short circuit. You are a danger to yourself and other users of the electrical installation. Clearly initial verification of this work was not carried out either before energising it.

EachPenny

t3rm3y wrote: »

Turned fuses on and light came on(possibly left in on position) tested by switching it off and it blew the fuse.

It sounds like you've wired the new switch up as a 100% efficient fuse tester. :eek:

I agree with pramsay13. If you've got to this point and you don't know how to fix it then the correct thing to do is to call in a professional.

Risteard

EachPenny wrote: »

If you've got to this point and you don't know how to fix it then the correct thing to do is to call in a professional.

Actually, the correct procedure would have been to do that before getting to this point.

t3rm3y

I can't see why it would be considered so dangerous?
I'm either going to wire it to the wrong line from existing rose and the light will only come on when other is switched on. Or it's going to do as I have done and blow the fuse.
I have checked some bits and think it may be because I ran the spur cable to a switch and from the switch I ran a 2nd cable to the light bulb by jumpering the browns together to com port and blues together to "1" port.
Looking at some wiring diagrams it looks as though I should have ran the spur to the light directly and then ran the 2nd cable to the switch...
I will check again when light. I do telephone wiring so am comfortable wiring and cabling but don't deal with electrics. But the principle should be simililar..yes I know the dangers are heightened but its a light bulb not a power socket.

EachPenny

t3rm3y wrote: »

But the principle should be simililar..yes I know the dangers are heightened but its a light bulb not a power socket.

230v is still 230v whether it comes out of a socket or through a lighting circuit.

Mains electricity also has the ability to rapidly overheat cables and cause fires, which would be a significant cause for concern in a short-circuit situation. You need someone to help you make your wiring safe again.

George_Michael

Risteard wrote: »

You are clearly wholly incompetent to be carrying out this work and have created a short circuit. You are a danger to yourself and other users of the electrical installation. Clearly initial verification of this work was not carried out either before energising it.

Something that I never thought would happen but I'm in total agreement with Risteard!

Grenage

t3rm3y wrote: »

I'm either going to wire it to the wrong line from existing rose and the light will only come on when other is switched on. Or it's going to do as I have done and blow the fuse.

Or it's going to ostensibly work, but be a dangerous installation - potentially killing someone else years later.

tacpot12

EachPenny has hit the nail on the head: you've created a short circuit, which the fuse has protected you from, but did it do so fast enough? If the 'fuse' was actually an MCB, it probably did trip fast enough to prevent any damage to the cables, but if is was an old rewirable fuse there is a chance that it took too long to trip and this has damaged the cable insulation. This damage could have exposed live wires anywhere in the lighting circuit, so you do really need to get an electrician in to do an insulation test on the circuit.

If the fuse that tripped was actually an RCD, you might have more problems than you are aware of.

onomatopoeia99

George_Michael wrote: »

Something that I never thought would happen but I'm in total agreement with Risteard!

I know. Never thought i'd see the day