Circuit tripping with nothing plugged in

Discussion in 'Electricians' Talk' started by Scott Edward Sharlotte, Nov 17, 2021.

  1. Looking for a bit of advice.
    I've got a circuit in my house that is tripping, despite nothing being plugged in.
    It will happen sort of randomly, although it tends to be consistently roughly at the same time for a week, then change and trip at another time for a week or so.
    I can switch the circuit straight back on no problem, and it will be okay for another day or two. It's been doing it for a couple of years and I've been unable to find a fault.
    The circuit next to the affected circuit on the board has now recently started to trip within the last couple of weeks.
    I've just had an electrician have a look and he found nothing. Tested the insulation on the circuit, all of the sockets and the Rcbos with no faults found. I've attached a picture of the invoice with what he tested.
    He is adamant it must be an appliance. But I am 100% certain that the circuit will trip with absolutely nothing plugged in.

    3 things happened around the same time it started. 1) telecom engineer drilled through my wall for an install. 2) new meter installed from EDF 3) next doors bathroom flooded.
    Bear in mind. It started in June of 2019. Nobody has been able to find the fault.

    Although he said if any of these were causing a problem it would have shown up. I trust what he is saying. He seemed good and is pretty reputable localy but I think I need a second opinion.

    Also my downstairs lights are flickering sometimes but there didn't seem to be concern about this.

    Does anybody else have any advice?


    Attached Files:

  2. Bazza-spark

    Bazza-spark Screwfix Select

    Unless he has made a typo those are rubbish readings. They should be in megohms with a minimum of 1 meg. 500 ohms is less than half of that and 50 ohms is close to being a short.
    seneca likes this.
  3. He was talking about 1 ohm being the minimum so he was probably talking in megohms. Would the readings still make sense if there was a typo?
  4. Bazza-spark

    Bazza-spark Screwfix Select

    If they are 500 megohms and 50 megohms, they are ok, but that isn't what he has written and any spark reviewing would take those readings as written and being rubbish. 1 megohm is the minimum, 1 ohm goes BANG!
  5. Yeh! There definitely isn't any bang, smoke or pop. It just quietly trips.
  6. Bazza-spark

    Bazza-spark Screwfix Select

    TBH I would find somebody else. If he is talking 1 ohm being the minimum I wouldn't trust him. He is out by a factor of 1,000,000.

    Is he NICEIC oe ELECSA or any approved body registered?
    sparky steve likes this.
  7. rogerk101

    rogerk101 Screwfix Select

    There are 1,000,000 ohms in a megohm, so 500 ohms is indeed a WHOLE lot less than half of a megohm ... in fact 500 ohms is 0.005 of a megohm.
  8. Yeh NICEIC approved.
    Seemed decent but yeh I get what you're saying. I'll definitely get someone else in. Cheers.
  9. Bazza-spark

    Bazza-spark Screwfix Select

    Yes, like I said in #6

  10. Lectrician

    Lectrician Screwfix Select

    Some RCBOs are susceptible to interference and can trip. I've seen LED wall dimmers cause RCBOs to trip due to the incorrect lamp bulbs being installed. The dimmers didn't like the wrong lamp bulbs and caused a completely different RCBO to trip when switched on.
  11. Strangely enough I've got LED spotlights in the kitchen.
    They used to be on a dimmer but i got it changed to a general run of the mill switch about a year ago because it was the wrong type of dimmer and wasn't working anymore , so I cut my losses and went for a normal switch.
    (Dimmer installed by previous owners and aparently shouldn't have been installed in the first place)
  12. The Happy Builder

    The Happy Builder Screwfix Select

    Has the circuit breaker been replaced?
  13. The full thing or just the units for the dodgy circuit?

    The guy tested the Rcbos and they were all good.
  14. The Happy Builder

    The Happy Builder Screwfix Select

    Presumably he tested the RCD function, but probably not the MCB function.

    Swapping a couple around is usually a simple test.
  15. Sparkielev

    Sparkielev Screwfix Select

    What circuit is tripping ? Does it say on your consumer unit
  16. Sparkielev

    Sparkielev Screwfix Select

    According to his spark he has rcbos
  17. It's my downstairs sockets. Nothing near any water or pipes..

    But...The circuit supplying my kitchen sockets has now also begun to trip at the same time within the last couple of weeks
  18. Yeh, stuck something in one of the sockets and made them trip.
  19. The Happy Builder

    The Happy Builder Screwfix Select

    Which is a combined RCD and MCB.

    From what has been said it is almost certainly a neutral fault on the circuit that has been tripping.
  20. sparky steve

    sparky steve Screwfix Select

    Neutral Earth fault perhaps?
    If the appliance is at fault, then switching off the appliance at the socket may not be sufficient to isolate the appliance from the neutral conductor. The reason for this is that sockets and switches can be either dual pole or single pole.

    A dual pole switch will disconnect the live conductor and the neutral conductor but still leave the earth conductor intact. A single pole switch will only disconnect the live conductor but leave the neutral and earth conductors intact. So a single pole switch will not sufficiently isolate a circuit to allow simple fault diagnosis! Therefore you need to physically disconnect any appliance on the circuit. Eg, remove appliance plug from socket. A PAT test should be able to confirm if an appliance is faulty or not.
    Presuming your RCBOs are single pole? and
    if the problem is in the supply circuit then
    Isolation cannot be as simple as tripping the RCBO because the RCBO only switches live. Equally if you have a circuit with a single pole MCB you have the same problem as with any single pole switched device. Essentially you need to manually disconnect the Neutral wires for each circuit being diagnosed.

    Therefore, All power off. all neutrals out of Neutral bar, test individually to earth.
    Last edited: Nov 18, 2021
    The Happy Builder likes this.

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