RCD Trips

Discussion in 'Electricians' Talk' started by cornish pasty, Jun 10, 2010.

  1. cornish pasty

    cornish pasty New Member

    500 L-N, L-E & N-E. Told him it was his hob. New hob arrives and fitted, trips the RCD. Disconnected all loads at cons unit, just hob connected, trips the RCD. Disconnected hob, doesn't trip the RCD. Told customer it must be a duff new hob although he doesn't believe me and I am doubting myself. Anyone got any other tests I can do. Cheers in advance
     
  2. cornish pasty

    cornish pasty New Member

    It should read, finished a kitchen extention and customer informs me that hob is tripping RCD. Went back and checked IR 500ohms L-N, L-E & N-E. Told him it was his hob. New hob arrives and fitted, trips the RCD. Disconnected all loads at cons unit, just hob connected, trips the RCD. Disconnected hob, doesn't trip the RCD. Told customer it must be a duff new hob although he doesn't believe me and I am doubting myself. Anyone got any other tests I can do. Cheers in advance
     
  3. Kwichy

    Kwichy New Member

    Induction hob I'd bet !
     
  4. syholl

    syholl New Member

    500 ohms is very low, not really acceptable. Something isn't right there....! How old is the cable...?
     
  5. seneca2

    seneca2 New Member

    500 ohms is very low
    -----------
    I hope you mean 500 Megohms and not 500 ohms Cornish or I wouldn't be surprised it trips! Also you haven't got N-E wired the wrong way around have you?
     
  6. sparky Si-Fi

    sparky Si-Fi Screwfix Select

    Put an IR test on the hob and check test results as C.O.P. in house I+T of electrical equipment if nothing else works to proove your issue with the client. .

    .5 Megs is an extremely low result on that cable

    Should be off the scale with loads dis-connected
     
  7. sparky Si-Fi

    sparky Si-Fi Screwfix Select

    Induction hob I'd bet !

    What a ball ache they are as well. . .
     
  8. cornish pasty

    cornish pasty New Member

    500 Meg Ohms
     
  9. state-it

    state-it New Member

    Was first hob new as well?

    If they've been in dampish storage you may need to cook the damp out of the elements for a few minutes.

    Run it off the RCD for a bit first and then see if it works on RCD.
     
  10. state-it

    state-it New Member

    Check IR of element spade fitting to hob chassis.
     
  11. Lectrician

    Lectrician Screwfix Select

    I assume when you say all load removed at board that you disconnected all lives and neutrals of the other circuits, leaving just purely the hob connected and nothing else?

    I may deserve a slap, but you have checked the neutral is on the correct neutral bar?
     
  12. sparky308

    sparky308 Member

    Test the RCD with no outgoing circuits connected - i.e. disconnect RCD completely from live and neutral busbars. If it tests OK, fault could be slight N-E leakage on any circuit. Hob can cause tripping whilst other loads don't because high inrush current means higher leakage current for a few seconds. You have to check N-E everywhere, not just on the hob circuit.
     
  13. sparky308

    sparky308 Member

    Should have added - you could try ramp-testing the RCD to see what current it's tripping at.
     
  14. cornish pasty

    cornish pasty New Member

    Many thanks for all replies, hob being changed on Thu, will let you know how it went
     
  15. unphased

    unphased Screwfix Select

    Cornish

    What exactly is the hob he's using, make, model, rating? Some of these hobs pull out RCDs mate and the type of RCD might need to be changed to stop this happening. I would advise checking with the manufacturers about this and see whether they advise RCD protection and what type. This will save any future embarrassment.

    :)
     
  16. seemless

    seemless New Member

    Can't wait till Thursday.

    Hob number 3 coming right up!

    Bit of a hobnob I'd say!
     
  17. fooman

    fooman New Member

    What exactly is the hob he's using, make, model,
    rating? Some of these hobs pull out RCDs mate and the
    type of RCD might need to be changed to stop this
    happening. I would advise checking with the
    manufacturers about this and see whether they advise
    RCD protection and what type. This will save any
    future embarrassment.

    what sort of RCD's UP ?

    How will the modified circuit comply with the 17th with removal of the RCD ??
     
  18. seneca2

    seneca2 New Member

    How will the modified circuit comply with the 17th with removal of the RCD
    -----------------------
    Maybe all the wiring is on the surface?
     
  19. Caddy

    Caddy Active Member

    what sort of RCD's UP ?


    ------

    You can get different types of RCD just as you can get dfferent types of MCB. If i remember its something like Type A, AC and B.
     
  20. cornish pasty

    cornish pasty New Member

    500Meg between all conductors and earth and I rigged up 2 x 2G sockets on a bit of 4mm T&E and plugged in 1 x 3Kw Kettle, 1 x 3Kw Fan Heater and 1 x 1Kw Drill. Proved to both that the circuit could take 7Kw, which was the rated output of the hob. All worked well. Connected the 4TH hob up, switched on, RCD tripped. Techie looked puzzled, rep was amazed. I F*d off leaving customer a bill for a couple of hundred quid for the time I had spent going backwards and forwards replacing hobs and double checking my install. Company rang today and it appears that this particular hob has an inherrent earth leakage problem and should not be connected to RCDs. Vwala. Be careful in the future.
     

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