RCB problem

Discussion in 'Electricians' Talk' started by Dave Blackburn, Jul 22, 2021.

  1. Dave Blackburn

    Dave Blackburn New Member

    Sat here this morning watching TV and power went off.
    I investigated and saw the breaker on one side of the panel had tripped. It would not reset. That side of the board was outside power (spare 10), burglar alarm ( now unused),lights first floor, sockets and shower. It’s the RCD that keeps tripping.
    Next I removed all appliances and it still wouldn’t work. I then tested each circuit individually. All circuits were fine. I then tried the power sockets on its own. It held. I then started to plug things in. First item tripped it.
    Removed the appliance and reset. Plugged another one in it too tripped it. This happened for every single different appliance plugged in. No more than one item at a time.
    Could the RCD be faulty?
  2. jonathanc

    jonathanc Screwfix Select

    or a fault on the sockets too. try loading the RCD up by turning stuff on on other circuits. if it does not trip my guess is a circuit fault not RCD but its a guess
  3. spirits are real 2016

    spirits are real 2016 Screwfix Select

    Have you got outside lights or sockets connected to that side it could be moisture inside them causing the trip..
  4. Dave Blackburn

    Dave Blackburn New Member

    Yes one circuit goes to a shed but even with breaker turned off the fault remains.
  5. spirits are real 2016

    spirits are real 2016 Screwfix Select

    It could still be a neutral earth fault in the shed it dosent matter if the mcb is turned off that just controls the live,, the earth and neutral would need disconnecting to the shed to separate it from the house you could always check in the shed for spiders they are known to trip electrics by shorting the terminals inside the sheds electrics.
  6. FlyByNight

    FlyByNight Screwfix Select

    The breaker only cuts teh LIVE side. If, for example, and outside socket had water in it or a spider causing a Neutral to Earth connection, the RCD may still trip.
  7. Dave Blackburn

    Dave Blackburn New Member

    Things a bit more strange. Had a sparky out this morning who left scratching his head.

    still not resolved.
    Kitchen power still up and running.
    Managed to get partial power back on but when something else was plugged in the breaker tripped again. Seems not to like four gang extension leads. Every one of those trips the breaker.
    With power on to sockets, if oven turned on the breaker for none kitchen sockets trips.
    Currently got extensions running from the kitchen, to the shed freezer, and one up stairs.
    Sparky has had sockets off and tested.
  8. MGW

    MGW Screwfix Select

    Typical earth - neutral fault. Earth and neutral with no load are the same voltage, as load is added the neutral starts to move towards line voltage.

    The problem is we have traditionally switched just the line, as to an electrician testing it is some times long winded, we start by looking at likely faults, but then it is a methodical bit by bit test, so very quickly we will find which circuit, but if for example the ring final, we split it in two, find which is bad half, then split bad half in two etc.

    But unless intermittent fault easy enough to find, but time consuming, where the problem lies is intermittent. Intermittent can be a problem.

    This is why my house all RCBO then only loose one circuit
  9. Bogle Crag

    Bogle Crag Screwfix Select

    Have look in the shower, sounds like a fault I was called to, traced it to a burnt neutral in the shower

    Had one last week, tripping sockets MCB not RCD found a slug inside a TV amp under the floor, keep an open mind and try to be methodical
    Last edited: Jul 22, 2021
  10. Jimbo

    Jimbo Screwfix Select

    Agree, it is the commutative effect of the leakage. It will hold until there is enough load and/or leakage elsewhere (eg anything with a switched mode power supply) to exceed the trip threshold. Shower would be top of my list to test.

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