Nasty Nip from wall sockets

Discussion in 'Electricians' Talk' started by ChrisM123, Oct 8, 2021.

  1. ChrisM123

    ChrisM123 Member


    Yesterday I experienced my first nip from a main circuit.. rather shocking I must say (tumbleweed moment).

    Confusion is that it was a first floor socket and I had switched off the fuse on the main fuse box. I did test two other sockets but stupidly didn't test the wires of the wires in question.

    As a non electrician I suppose I am surprised that cutting the power to a fuse didn't cut all of the sockets as the fuse details... is this a common occurrence?

    The house is less than 5 years old.. Should sign off of the electrics not spot this?

  2. Turning off the MCB for a circuit should isolate it. That doesn't mean that the socket was on the breaker you turned off.
    tore81 likes this.
  3. SIRJOHN19

    SIRJOHN19 Active Member

    Many houses are not wired as 1st or 2nd floors etc. It’s wired as is convenient for the cable runs. Never never assume what’s written on the consumer unit as gospel. Always test with an approve tester and then test again. Here endeth lesson 1
    tore81 and michael862 like this.
  4. MGW

    MGW Screwfix Select

    In the main ring finals should be split side to side of the house, as it needs less cable that way, and means a better earth loop impedance, when I fitted a new consumer unit the labels were all pre-printed upper and lower floor, so needed to write my own labels.

    The on the cheap method is split up/down, because lights naturally are split upper and lower, and lights should not go out if you get a shock from a socket, if wiring on the cheap and only using two RCD's then the sockets also need splitting up/down to match lights, pre the days of RCD protection it was better side to side, but using RCBO's it can still be side to side so better quality homes still side to side.

    However the testing procedure means it really does not matter, you always test for dead, then test the tester is still working with proving unit, so only problem is when it switches on while working on it, which is why I always use Neon screwdrivers, they are a good second string to the bow, and also alert one if there is a borrowed neutral.
  5. Comlec

    Comlec Screwfix Select

    You have learn a valuable lesson. Never trust a label - always test for dead.
    I am sure you are not the only one in here to find out the hard way.
    At least you survived to tell the tale.
  6. koolpc

    koolpc Screwfix Select

  7. sparky steve

    sparky steve Screwfix Select

    I would recommend in future, isolate using the main switch on your consumer unit, and always test for dead.
  8. Truckcab79

    Truckcab79 Screwfix Select

    Get yourself a cheap non-contact voltage tester. Worth their weight in gold. I’m not an electrician but often have to remove and replace switches etc if decorating. I’m paranoid about anything that I haven’t personally done so I always test , isolate and then test again. Once had a bathroom on first floor that was inexplicably wired separately to the rest of the floor lighting circuit and was in fact still attached to what the client had told me was an entirely redundant old consumer unit that was no longer part of the house wiring. It wasn’t…..apart from this one light fitting.
  9. PandA3

    PandA3 Member

    Worth knowing that Not all power circuits are designed as 32a Ring Final sub circuits for sockets. Many of the big boys prefer 20a radials, which arguably is a better/safer design. So there would always be more than one power circuit if using radials.
    You would expect the DB to be labelled correctly but should always test for dead before working on.
  10. bright_Spark

    bright_Spark Screwfix Select

    As an electrician I would never use a cheap or expensive non contact voltage tester for testing if a circuit is dead. A non contact voltage tester can only be used as an indicator in certain circumstances and in the right hands. Mainly used to test for live and certainly not used to test for dead. Only ever use a voltage indicator to test for dead having proved the test meter on a known source first.
  11. Tony Goddard

    Tony Goddard Screwfix Select

    A two pole tester is, in my mind, a must have, even for DIY work, if you havn't got one, get one - really useful thing and saves lives, such as...

    Like everyone in the trade I have had various jolts down the years, the most ammusing in hindsight was under a female customers bed. She had an issue with a light in the dining room, no earth, wanted a brass light. I ascertained there was a CPC on the circuit, but only a two core flex was coming through the ceiling.

    In the bedroom above, under the huge immovable 4 poster was a trap board on the bare boarded floor, I couldn't (being somewhat rotund, winter insulated) get all the way to it, but I could get under the bed far enough to open the trap. I planned to pop my hand in, pull up the JB and find the earth.

    Unfortunately I grabbed the wrong JB (which I hadn't thought would be there, ring circuit) and it didn't have its lid on, bang!! it caused my head to go back and crack the underside of the ladies bed - she thought it was hysterical, lead to her making me lunch, a few weeks later a dinner out, 12 years later I'm still paying for that - had I not grabbed the wrong JB I'd have had my £50 fee, been on my way, and still been able to make my own decisions:)
  12. sparky steve

    sparky steve Screwfix Select

    Wondered where you were going with that one Tony? Thought you were going to tell us you had getting a jolt from some other electrical device under the bed:oops::eek::D
    Bazza-spark likes this.
  13. SIRJOHN19

    SIRJOHN19 Active Member

    Don't get me started about working in peoples bedrooms, another (Educating) world!
  14. SIRJOHN19

    SIRJOHN19 Active Member

    No comment
  15. Truckcab79

    Truckcab79 Screwfix Select

    Cheers for that. All I’ve ever used. Shows why I’m not an electrician! Will have a look at the kit suggested in the next post.

    Forgive my ignorance but if the live non-contact tester doesn’t register, what’s the difference between that and ‘dead’. I’m assuming from what you’re saying that there’s still a risk?
    Much appreciated.
  16. Bazza

    Bazza Screwfix Select

    Those magic wands sometimes lie to you. They can pick up voltages from elsewhere and also voltages can be shielded from the device.
    They are limited in their use. Pointless for most fault finding as they cannot detect the presence (or lack) of a neutral which is half of a circuit.

    Use a two probe voltage tester and learn about safe isolation procedures. It could save you, and we need all the truckers that we can get!
  17. bright_Spark

    bright_Spark Screwfix Select

    They are really used to see if there is any voltage on a cable in some senarios, if it lights up then all well and good but they can miss a lot of detecion, so even if they do not light up it doesnt mean that voltage is not there, they have a terribe fail rate. The only way to know if a cable is live is to use a voltage tester. You can be sure that it is dead before touching the bare conductor
    Last edited: Oct 9, 2021
  18. FlyByNight

    FlyByNight Screwfix Select

    As an experiment, find a lamp with flex and plug. Try the voltage pen on teh flex - run it down te side where the live is and it will illuminate, down the neutral side and no light!
  19. bright_Spark

    bright_Spark Screwfix Select

    To test correctly for dead. You first prove that your voltage tester is working by placing it on a known live source and seeing it iluminate. Then on the cables you want to know is dead, you would test between Live and Neutral, Live and Earth, then Neutral and earth. Once this proves dead you then test the voltage tester again to make sure it was still working during the test, you can then touch the bare conducter. You cannot conduct the same test with a non contact pen.
    SomeOfTheGear and Truckcab79 like this.
  20. Truckcab79

    Truckcab79 Screwfix Select

    Funnily enough I’ve always found the opposite. They tend to give a register of live if they are anywhere near one. That’s been good enough for me in the past as I don’t care which one is live so long as I’m not touching it. :)

    Thanks to all for the excellent info. I’ve now purchased the suggested probe type. Money well spent I’m sure.

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