Tricky fault......ideas please

Discussion in 'Electricians' Talk' started by Jimtnash, Mar 13, 2018.

  1. Jimtnash

    Jimtnash New Member

    Hi,
    Have an 18 month old Consumer unit, suddenly started tripping out RCD, lighting circuit mcb is the culprit.

    Have: replaced rcd , replaced mcb, removed lamps. Not a borrowed neutral....... ideas please.

    Many thanks.

    Jim
     
  2. JP.

    JP. Screwfix Select

    Is the cu a Crabtree Starbreaker Jim?
     
  3. Jimtnash

    Jimtnash New Member

    J.P.
    Thanks for prompt response.....no it is a schneider Easy 9
    Jim
     
  4. Dr Bodgit

    Dr Bodgit Well-Known Member

    Could be a loose or bare wire, neutral touching backbox or earth for example.
     
  5. JP.

    JP. Screwfix Select

    Is it the upstairs or downstairs lighting circuit which is tripping the rcd Jim?
     
  6. 14th edition

    14th edition Well-Known Member

    So if you disconnect the L/N for the lighting circuit and test for IR what readings do you get?
     
  7. JP.

    JP. Screwfix Select

    Sounds like the downstairs lighting circuit to me. Are there any external lanterns on this circuit Jim? ie..security light/s/bulk head type units/lamp post/s etc etc?
     
  8. Jimtnash

    Jimtnash New Member

    Yes - there are external lights on this one (it is downstairs lights) - will try and track them down -thanks jim.
    (Have looked for loose wires /shorts but all good dr bodgit -thanks though)
     
  9. Bazza

    Bazza Well-Known Member

    RCDs are made to trip when there is an earth leakage. There are stories about RCDs that have tripped because of an L-N short circuit, or a loose wire but generally they don't care about such things.

    Unless you spot something obvious in the soggy outside light department, then you'll be much more likely to find a problem using proper test equipment.
    Guessing and hoping is a long, frustrating road to nowhere.
     
  10. Jimtnash

    Jimtnash New Member

    Guessing & hoping worked !! Found stray, loose live after couple of hours. Thanks for input one and all !
    Jim
     
    Bazza likes this.
  11. Bazza

    Bazza Well-Known Member

    Congrats. I guess it works sometimes!
     
  12. Dr Bodgit

    Dr Bodgit Well-Known Member

    Sometimes you actually find the needle in the haystack!
     
  13. JP.

    JP. Screwfix Select

    Where was that stray loose live Jim?
     
  14. Lectrician

    Lectrician Screwfix Select

    Where does this assumption come from?
     
  15. Lectrician

    Lectrician Screwfix Select

    If turning off the lighting MCB cures the tripping issue, it won't be a N to E fault.
     

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