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Discuss Large oven tripping RCD in the Electrical Forum area at ElectrciansForums.co.uk.

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  1. al1981
    Offline

    al1981 New EF Member

    Location:
    Lincolnshire
    Hi all.

    Looking for a bit of advice.
    Customer has a new large induction rangemaster cooker with a total power of 14.8kw.
    Currently on a Hager board with a 50a b mcb and an existing 6mm cable.
    As soon as oven was switched on it tripped the RCD.
    Taking diversity into account the cable should be fine.
    Is the breaker too large?
    Insulation resistance test comes back fine.
    Should I try a smaller breaker?
    The oven has the potential to pull 60 + amps and they’ve said they want all 3 ovens on and the hob so I’m wondering if it needs it’s own 63a RCD and a 10mm?

    I don’t want to stick it on a 40a and have issues later on.
    I guess there’s also the potential that the element had gone as well?
     
  2. Lucien Nunes
    Offline

    Lucien Nunes Mercury Arc Rectifier Respected Member

    Location:
    London
    Numbers please! Sheathed heating elements that have stood around sometimes leak badly until they have been baked out, but this would show as very low insulation. So it's possible the insulation test did not actually test the elements, if there are relays in the control circuit that might have isolated them. It has been known for elements to need baking off the RCD until they come up to spec.

    What is the RCD serving? Much of the installation i.e. may be near its limit anyway?

    Eh?? What has OCPD rating got to do with leakage?
     
    • Informative Informative x 2
    • Like Like x 1
  3. Joseph staniforth
    Offline

    Joseph staniforth New EF Member

    Location:
    Rotherham
    Business Name:
    Westfield electrical services
    Is it a new oven? Have this problem a lot with new kitchen installs, the ovens are stored in cold warehouses, condensation on the metal can cause continuity between line/earth
    A lot of the time they send their engineers out who advise the cpc is disconnected to allow the oven to heat up and get rid of condensation, I always advise how dangerous this is and suggest to the customer they insist on a replacement.
     
  4. Marti
    Offline

    Marti Electrician's Arms

    Location:
    Romford Essex
    Business Name:
    Jigsaw Electrical Services
    Does this happen with anything / everything else on the board on? Could be the major leakage is elsewhere but 5 - 10 miliamps earth leakage from the oven is enough to hit the limit of a 30mA RCD. What 's the ramp test for the RCD? Finally, does it happen with the oven empty? I had one that tripped only when cooking, never testing and the moisture was shorting the oven. Raising the temperature slowly dried out the internal surfaces and it was fine!
     
    • Like Like x 2
    • Informative Informative x 1
  5. Matthewd29
    Offline

    Matthewd29 Regular EF Member

    Location:
    Belfast
    Changing the breaker size will have absolutely no effect on the rcd tripping or not, have you tested the elements or just the cable feeding the oven?
     
    • Like Like x 1
  6. Murdoch
    Offline

    Murdoch Electrician's Arms

    Location:
    Woking
    Do you think that the 50a mcb protecting a 6mm cable is ok?
     
    • Like Like x 2
    • Agree Agree x 2
  7. buzzlightyear
    Offline

    buzzlightyear please let me back in to the prison cell. Electrician's Arms

    Location:
    star command
    The op may has well put it on bell wire ,hay mad M .
     
    • Like Like x 1
  8. Wilko
    Offline

    Wilko Electrician's Arms

    Location:
    Berkshire
    Business Name:
    Wilko Electrics
    Hi - those cookers are recommended by manufacturer to be on an rcbo as they expect 8mA leakage. Perhaps confirm if this is the problem by turning off any other circuits using that RCD.
     
    • Like Like x 2
    • Agree Agree x 1
  9. Pete999
    Offline

    Pete999 Forum Mentor

    Location:
    Northampton
    Business Name:
    None
    Call an Electrician in to take a looksee at the problem
     
    • Agree Agree x 7
  10. dmxtothemax
    Offline

    dmxtothemax Regular EF Member

    Location:
    Australia
    Business Name:
    David Haddock Electronic Repairs
    check the power factor,
    it is possible that the power factor trip the RCD
     
  11. DaveChase
    Offline

    DaveChase EF Member

    Location:
    Hampshire
    It sounds like the RCD tripping is the only thing stopping the 6mm cable from melting at the moment.

    Whatever the issue is (& I'm inclined to agree that the oven is probably tipping the balance with the real fault being elsewhere) it's lucky it did trip as it could have just prevented a much more serious situation!
     
    Last edited: May 15, 2019 at 1:34 PM
  12. Pete999
    Offline

    Pete999 Forum Mentor

    Location:
    Northampton
    Business Name:
    None
    Having a Blonde moment Mate, please explain for an Oldie.
     
  13. john waters
    Offline

    john waters EF Member

    Location:
    sandy
    Business Name:
    ebs ltd
    50 amps on a 6mm that needs sorting out 1st
     
  14. Pete999
    Offline

    Pete999 Forum Mentor

    Location:
    Northampton
    Business Name:
    None
    I was asking out of curiosity that's all.
     
  15. Taylortwocities
    Offline

    Taylortwocities Electrician's Arms

    Location:
    Oxfordshire
    Yes figures on the IR test. And test the appliance too. In fact, do that first. After you have corrected the MCB size on that circuit.

    Oh hold on. If you are a trained electrician, you really need to check your college notes. You have forgotten some essential basic things.
     
    • Optimistic Optimistic x 2
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