Floodlight fitted, but no power.

28 Mar 2011
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United Kingdom
Yes, there's a moral to my story, and its probably "leave this stuff to the experts".

Fitted a floodlight on the front wall of the house, intending to cut into the lighting circuit cable in the loft of our bungalow and fit a junction box to take the supply for the floodlight. Because there was insufficient slack to allow me to reconnect the old circuit cable in the junction box, I extended the cable using a connector box, then made the connections for the two ends of the circuit cable and the floodlight in the junction box. No power. So I disconnected the floodlight, remade all the connections, still nowt. Tried remaking all the connections several times, but without success.

Lacking testing equipment, I had identified the lighting cable by tracing it back from the nearest ceiling rose. There are two lighting cables from the rose; one disappears into the ceiling, so must go to the switch, the other is routed with other cables to the CU, and its the latter one that I cut into for the floodlight supply. All other circuits are working OK.

Anyone any idea what I've done wrong? Thanks in advance
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Sorry chaps, when I said "no power", I meant the entire lighting circuit had gone off.

I've identified the problem, which was simply lack of observation on my part. I turned off the MCB for the lighting circuit to work on it, and while I was in the loft the RCCB tripped. So I must have touched two wires together, or summat like that.

I didn't even notice that the RCCB had gone off when I went down to turn the MCB back on and check the circuit, probably because sometimes you only notice stuff if you're expecting it. It only occured to me when I noticed that the shower and two sockets downstairs were also off, being on the same side of the CU as the lighting.

Thanks anyhow for taking the trouble to reply.
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while I was in the loft the RCCB tripped. So I must have touched two wires together, or summat like that.
N & E.

Turning off the MCB only isolates line, not neutral, so when that contacts an earth the RCD trips.

Lacking testing equipment
A lack which you should remedy. I'm assuming that you didn't use a par of scissors to cut the wires, or rummage in the knife drawer for something to use on the heads of screws? If you are going to do electrical work then electrical test equipment is just as essential. Without it you cant fault find so easily, and most importantly you can't test for dead to confirm that you relly have isolated what you're going to be fiddling with.

Take a look at this: https://www.beha-amprobe.com/en/products/electrical-testers/junior-set-and-kits/amprb-eu-03-a

Looks ideal for a household starter set - multimeter, 2-pole voltage indicator and dedicated continuity tester, all in a handy case.
Many thanks. After doing a modicum of research the other night, I did manage to work out why the RCCB tripped. And yes, testing equipment will be heading this way before I entertain the difficult and dangerous world of electrics again. I did buy a very cheap testing device years ago, but the instructions were so utterly opaque that I never worked out how to use it and eventually it went in the bin, along with the scissors for cutting wires.

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