I would have thought that the switch in a mains socket, especially one designed for outside use, would be double-pole (ie it switches off both live and neutral), so it wouldn't have mattered if contact was made between the neutral and earth wires of the cable from the plug to the appliance. But I could be wrong. Maybe only the live was switched off, and the neutral-earth contact was what triggered the house RCD.
That's the problem with Thinking, about Real Stuff...
I would have *thought* Britain would be 100% nuclear powered by now...
Many socket switches are double pole, but there is no requirement for it and cheaper ones often aren't.
The house RCD tripped according to the OP which would not have happened if the SO had a double pole switch.
You are standing on a wooden ladder, and neither lights. You touch the live wire you just tested while touching the water pipe...
Thomas Prufer
I was annoyed that this happened to me, because I never buy single pole sockets. But in this case the socket was one I'd installed from my collection that I'd removed from somewhere else, and I hadn't thought to check whether those were single or double pole.
It's a bit surprising that being double pole hasn't become mandatory for the extra few pennies per socket it costs, in particularly due to the risk of neutral faults (lose the neutral upstream and a switched-on appliance like a heater can turn the neutral downstream into a live).
Are there any situations where a DP switch wouldn't be feasible?
Theo
I assumed a neon screwdriver works even if the user is not earthed. It certainly gets a lot brighter if you touch earth, which suggests to me that an earth connection is not needed to make the lamp glow. Am I dangerously wrong?
Actually the inherent 'capacitance-to-ground' of a human body is generally enough to light a neon.
Even up a ladder.
Otherwise people in ribber soled shoes wouldn't light them, either.
Offhand I cant think of any, but to the best of my knowledge DP switches are ONLY common for switched spurs, the average domestic wallplate is live switched only.
Screwfix does sell DP, but they are a lot more expensive, hence its safe to assume that in a typical installation not done by a UK.D-I-Yer, they will be SP.
Which is entirely adequate for the intended purpose.
This is what I was alluding to in my message.
Yes, could there be some secondary return path being used that nobody had thought of? I guess only a test now would show the reason for this. He also says flex, and I wonder how old it is and if its been damage somewhere or got some moisture in the circuit. Brian
Yes, I have an armoured cable not currently in use from a spur. It originally went to a shed. I intend to get a sighted friend to put a sealable box in theirs wire outside near the patio, with a 13A socket and a switch inside for the rest of the cable, not yet connected, and shield that switch so it cannot be accidentally turned on till the shed is wired up, OK so its not been built yet.. I'm assuming such boxes exist out there for this purpose. I don't want to use some oddball mains outlet, as on dry days it will be used to power normal appliances. Brian
A neutral earth short will typically trip a RCD - so there is no real need to go looking for more complex answers. (Occam's razor and all that!)
My comment was really just pointing out that Gareth's assertion that L&N were transposed, would if true, have given a very different result when cut through. "Bang, flash, fuse / MCB trip and missing lump out of the side cutters etc!"
It is probably a "plug in" garden socket - you can get these as pre-made sets. Normally an externall rated socket (sometimes on a spike do you can plant it in a lawn etc), and then a run of weatherproof flex back to a plug.
Again it did not trip in normal operation - only when he attacked it with side cutters!
I would have thought the ZETA machine demonstrated on TV in the sixties would have been churning out electricity too cheap to meter by now.
Why not have none? The things are 'kin liabilities. Get a proper tester!
Not good criteria for safety critical test gear designed to prevent injury and death.
Because they are too easily fooled but invisible factors. e.g. if you are "live" by virtual of capacitive coupling, the live thing you try to test will show as dead, and the neutral thing as live. If you lack a path to ground they may fail to light. They are dim and hard to see in daylight. They form a direct connection between the operator and mains via a resistor / neon. Let's hope there is no moisture in there from being in pocket on a warm day.
They will to an extent usually - any large conductive body will act as a source of free electrons - and so look like an earth. However things like skin dryness, humidity etc will affect the performance.
The dangerous bit is relying on them when you have already highlighted that the results are not conclusive (i.e. a dim glow might not be seen in daylight)
On Fri, 11 Aug 2023 12:57:04 +0100, John Rumm snipped-for-privacy@nowhere.null wrote: [snip]
What would you recommend for occasional DIY use with no aspirations to become a true professional and taking budget into account?
Possibly
However, he cut the flex *feeding* the external socket - not one after it. So its switching arrangement was moot.
The switching arrangement on the socket in the house feeding the flex
*would* have had a bearing though.Yup
Yer-but, doesn't a Volt Stick work in the same way? It relies on the body capacitance to ground, which if capacity coupled to live will also make a live conductor show as dead?
I think you need to do a bit of electrical engineering study. If you are standing on a live wire using a neon screwdriver to check if its live, you are a more clueless clot than you normally appear.
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