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my RCD smells funny.......

Discussion in 'Computers, Cabling & Other Miscellaneous Hardware' started by penguineer, Mar 9, 2014.

  1. penguineer

    penguineer Full Time Elf

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    Is that bad? :eek:

    [​IMG]

    [​IMG]

    Just thought I'd get a rise out of the sparky types :p

    FWIW - decided to test the RCD and the test switch jammed inside the housing(wouldn't pop back out), so a few sparks, a few funny smells and........

    I missed seeing any magic smoke - I am incrediby disappointed as I am sure that the magic smoke is what keeps these electrickal things working so the absense of smoke clearly demonstrates that I must have bought an inferior unit.....

    Cheers!
     
  2. Ɠαяєтн

    Ɠαяєтн Mae gen i C.L.A.P ei heintus iawn

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    The component that has failed is the test resistor, normal for a 30mA RCD this is 6.8K Ohms 2W and goes across the active and neutral on the load side. When the push button is pressed this puts the test resistance across the output and causes the RCD to trip. So this goes in line with what you said, when you pressed the test button.....

    From the picture this looks like a single pole RCBO, combined RCD and MCB. This makes no differnce for the failure but will have to be replaced with a similar unit. It just appears from the picture that the resistor failed, unfortunately this can sometimes happen. I assume that this is from your house switchboard. I would very much doubt there is anything else wrong, but for the sake of just being sure I would employ a licensed electrician to check the circuit and install a new breaker.
     
  3. OP
    OP
    penguineer

    penguineer Full Time Elf

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    This was from one of those "power brick" things - four switched outlets and an RCD. The rest of the circuit it was plugged into is fine.

    After it snap, crackle and popped I took the whole thing apart - it's meant to be a non-serviceable item and I can handle that, also one of the three-pin outlets wasn't working.

    The RCD component itself looks like a regular unit you can mount in a switchboard including the rail mounts on the back of it, but in this case it is held in place by studs on the inside of the power brick.

    Cheers!
     
  4. David_AVD

    David_AVD Bite my shiny metal ass!

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    Wouldn't the resistor (and button) go from the supply neutral to the load active? If it went across the load A & N, how would that be any different to a real load ?
     
  5. AAH

    AAH I love blinky lights :) Community Project Designer

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    Would you believe it probably goes from Active to Earth so it actually generates an earth leakage fault?


     
  6. Ɠαяєтн

    Ɠαяєтн Mae gen i C.L.A.P ei heintus iawn

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    Hi David,

    Thanks for the question and sorry my post wasn't clear. The ones I have had experience with go from the supply active to load neutral to give the differential current. The same would work as you suggested supply neutral to load active.

    Alan, some RCD/RCBOs do have an earth lead but the most commonly used only have active/neutral, mainly due to cost of not needing the additional cable. Residual Current Devices sense the imbalance of active and neutral currents and therefore will trip in case of a small leakage (10-30mA) to earth on the load side.

    The external RCD tester I use however does go to earth, it tells me trip time and current to prove the RCD. Front test buttons on RCD are more a functional test for end users.
     
  7. Jago

    Jago New Elf

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    You cant take it to earth as there is no earth on a RDC only active and neutral.

    However neutral and earth are bridged anyway in the board.



     
  8. battle79

    battle79 Full Time Elf

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    I'm guessing they where thinking commercial RCDs with the little white earth tail.

    If the test switch got stuck then I'd just replace the whole unit. Only $30 or less for noname brand.

    Cheers,
    Rowan
     
  9. multicast

    multicast Senior Elf Generous Elf

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    Please don't try to fix this.. Get a new one. And test regular.
     
  10. OP
    OP
    penguineer

    penguineer Full Time Elf

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    No intention of fixing it - took it apart to see where the magic smoke cae out of. Many of the bits inside had to be drilled to get out so it wouldn't go back anyway.

    New RCD brick(better one) was bought some time ago.......

    Cheers!
     

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