Naive electricity supply question ...

That is exactly the procedure that is supposed to be followed for all such tests, regardless of device type.

But are you paranoid enough? The orthodox practice is (as Theo said) to test before /and/ after.

Still leaves room to worry - e.g. about intermittent faults.

It sounds as though the switch at the socket was in the neutral, so you shorted live to earth with the stated result.

Only a guess though, and it's LONG time - fifty years, in fact - since I did any electrical work.

OP here: fantastic -- thanks chaps. Seems to me, then, that all is in order, except for this brain of mine, which forgot about making sure a flex is not plugged in _at all_, if you're going to snip it shorter!

Like Pete said earlier: "Today I am a little wiser".

Best wishes all .. I don't come here so often these days: the older I get the busier I seem to get: "what's that all about then?!!".

John

Did you read the rest of the thread before posting !?

I've spent a lifetime tripping RCDs, because I've (for one reason or another) only interrupted the live connection (by pulling the fuse/killing the MCB for the relevant circuit in the CU)

Short Neutral to Earth and that's what happens. The only way to avoid it happening, is to kill the L _and_ N at the first double pole switch upstream, which is normally at the RCD anyway !

This is an area where RCBOs are so much better. No accidental tripping of the other circuits due to a shared RCD.

I certainly hadn't read the post to which I am now responding. Or, in fact, any others except for the OP.

Or cut the cable in more than one bite... cut one conductor and bend the cable a bit to open up a gap, then snip the earth, then the final conductor.

The main culprit for me is pulling the three exposed ends back through a hole. Of course, if I spent an extra 10 seconds, sticking some insulation tape round the neutral.....

Cut them at slightly different lengths....not that I've ever rememberd to do that!

Yep, it shows.

Sods law says it would get pulled off as it drags against the edge of the hole and the bare end would promptly spring across to the earth wire.

This is the main reason that when the house was rewired I specified RCBO.

Prior to that my fumble fingers kept shorting neutral and earth and knocking the electrics off.

Cheers

Dave R

I may be more paranoid. I flick my finger across the 'live' wire just in case the neon screwdriver has failed.

Test the tester make the test test the tester

I am glad.

I went to university almost immediately after coming out of my time and eventually became a worker by brain, as some literature describes it.

I recently had a similar conundrum on my boat. I wanted to re-route a wire that I knew was the live 12v supply to a bilge pump. It was routed through various cable ties and I needed to pull it out and I didn't fancy digging around in the nether regions of the bilges if I blew the fuse that preotected it. ... not to mention that it was a biggish fuse and there's x hundred amp hours of batteries the other side of it.

So I did wrap some insulating tape around the bare end before pulling it about and, to my satisfaction, it didn't touch anything.

Why not have two neon screwdrivers? They're cheap and readily available. What would be the chance of both failing at the same time? Test both on the "live" wire. If only one lights, check the neon which doesn't light, or mark it as faulty and just use it as a screwdriver.