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Is my RCD wired up correctly?

Discussion in 'Electrics UK' started by sotal, 15 May 2016.

  1. sotal

    sotal

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    The RCD tripped this morning. I went to reset it but it wouldn't reset. So I went through the normal procedure of disconnecting everything.

    Eventually after disconnecting everything, I was able to turn the power back on.

    The RCD covers five circuits:

    Main house Ring Main
    Extension + Garage Ring Main
    Cooker
    Main Bathroom Shower
    En-suite Shower


    The lights and the CH is then on separate circuits not covered by the RCD


    Now if I plugged pretty much anything into the Main House Ring - then the RCD would trip - even plugging a phone charger in (without phone) would trip the RCD. The only thing I managed to get on was the microwave which would show the time and menus etc but as soon as you started it going the power would trip.

    The Extension + Garage Ring was similar but low power devices would work - I even managed to plug the fridge freezer in via an extension lead and that would run off that Ring Main but things like the kettle or the toaster again tripped the RCD.

    The Cooker circuit comes to a switch in the kitchen which gives a socket as well. If I used the socket then again low powered devices were OK but high power devices would trip the RCD. If I put the oven on then it would trip straight away (even the light and fan without heater element).

    Both Electric showers just tripped the RCD too.


    No sockets or lights have been touched or messed with recently.

    So given the above I figured that the RCD itself was the only common item, so I nipped out and got an exact replacement. Fitted it and had the exact same symptoms.

    I was at a bit of a loss by this point so we worked back through what had happened - it turned out that it was my wife who first realised that something was wrong. She plugged something in, in the spare room and it didn't work - so she took the item to our bedroom and plugged it in and it still didn't work. She then realised the power was off.

    So I took this item (sewing machine so fairly low powered) and plugged it into the extension ring and it worked fine - so it wasn't the cause of the problem.

    So I decided to work through what things it had touched, as it didn't work in the spare bedroom socket I decided to look there first. The socket itself looked fine (old - probably 1970s - single socket). So I removed the screws to check the wiring - all was secure with no nicks from the screws. I removed the wires to be sure. Once the wires were removed I checked the electrics again in the house and all was fine. I put the socket back on again and it all went funny again. I replaced the socket with an old single socket I had in the lying around in the garage and everything is working again.

    I've got to admit I was lucky to find it, I wouldn't have thought that logically the socket could have caused those problems. The socket has been in daily use with no issues before - the iron is normally plugged into it.

    So on to my questions!...

    First - should that have happened like that?
    Second - how did it affect the other separate circuits?
    Third - is it wired correctly? The instructions with the replacement don't sound like how it is wired! I put it back exactly the same as the old one though as it has worked fine for the last 10 years!

    The instructions made it sound like only the top or the bottom terminals should be connected. Ours was connected with live and neutral going into the top. At the bottom the one below the live connection is connected to the copper bar which goes to the bottom of the MCBs and the bottom one under the neutral one has another blue neutral wire coming out of it. Is that correct?


    The consumer unit has been fitted for about 10 years - it was one of the first jobs we had done when we bought the house. We had the consumer unit moved inside (was originally outside in the meter cupboard) and we had the extension and garage ring put in as the whole lot was previously on a spur from the house ring. This was all fitted by a proper electrician and was tested at the end etc.
     
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  3. EFLImpudence

    EFLImpudence

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    Unusual but could be a faulty socket.

    The reason something on another circuit would trip the RCD is because all the circuits are connected.
    Even switching off an MCB still leaves the neutrals and CPCs(earths) all connected and current flows through the neutrals (or Lines(lives) if still switched on) to the fault and then to earth.

    http://www.diynot.com/wiki/Electric...ergised-circuits-with-Neutral-to-Earth-faults
     
  4. EFLImpudence

    EFLImpudence

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    Oh, and it seems you have wired the RCD correctly.

    Obviously all four terminals have to be connected.
     
  5. sotal

    sotal

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    Excellent - thanks for the reply.

    I'm glad it is sorted without too much expense (just the RCD which I didn't need!)

    I still think I was lucky in finding the fault - will have to dismantle the socket to see if there is an obvious reason inside.
     
  6. Spark123

    Spark123

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    It sounds like a neutral to earth short from your description. Any loading and too much current flows down the earth wire and the RCD trips. It could be the neutral wire somehow connecting to a metal back box.
     
  7. bernardgreen

    bernardgreen

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