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MCB FAULTY? Help!

Discussion in 'Electrics UK' started by JayDiy, 29 May 2018.

  1. JayDiy

    JayDiy

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    Wonder if anyone can help, my cooker suddenly switched off so logically I went to the fuse box to see what tripped, To my surprise NOTHING had tripped, I had surely expected the 40amp mcb to have tripped so is there something wrong with the mcb despite not tripping? I am puzzled. Is this even common, l t me know guys.
     
  2. crystal ball

    crystal ball

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    Might be a loose connection somewhere I would start at the cooker switch, power off of course
     
  3. oldbutnotdead

    oldbutnotdead

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    Some MCBs don't have much of a visual trip indication- have you tried pushing the MCB to the OFF position then back ON? Is there an RCD covering that block of your consumer unit? Is that still ON? After that you're into some detective work- is the cooker hardwired (via a cooker switch) or is there a 13A plug somewhere in the circuit? Does the entire cooker not work or is it just the oven or rings that don't work?
     
  4. JayDiy

    JayDiy

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    Yes I tried switching on mcb on off also the rcd circuit has not tripped i checked the terminal block behind cooker, there's no voltage reading despite the mcb in ON position it's baffling me
     
  5. crystal ball

    crystal ball

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    Do you have a switch somewhere? might be hidden in a kitchen unit, what are you using to test for voltage?
     
    Last edited: 30 May 2018
  6. oldbutnotdead

    oldbutnotdead

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    Did you meter live to earth as well as live to neutral at that terminal block? Does sound like a loose connection somewhere, time to knock the power off and check the whole circuit.
     
  7. Taylortwocities

    Taylortwocities

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    Ok. But have you done the obvious test:
    Is there voltage leaving the MCB itself?
     
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  8. JayDiy

    JayDiy

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    there's no other switches behind the cooker only the cooker socket outlet which I tested with a multimeter for voltage across live and neutral with mcb ON but no voltage detected so obviously theres no current flowing from mcb to this point? I haven't actually tested from the fusebox to see if voltage is leaving the mcb, ill check that tonight after work, thanks for your help so far, will keep you posted.
     
  9. Taylortwocities

    Taylortwocities

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    You need to understand the difference between CURRENT and VOLTAGE

    The only time that you will get CURRENT is if there is a LOAD on the circuit (a cooker in your case).

    You need to test for VOLTAGE only, at this stage. Take a logical approach. Start at the supply source (consumer unit). Check voltage out of the MCB. If voltage is there, then its time to look elsewhere.

    Also, always test between line and neutral and also between line and earth.
    Don't forget that if the neutral is missing/faulty then the live will APPEAR not to be present(y).
     
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  10. JayDiy

    JayDiy

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    Sorry I meant to say voltage NOT current, my bad, anyway I’ve just checked the voltage at the mcb and it’s ok so it seems the mcb is not faulty, I need to look elswhere now as you guys have suggested, I’m going to try and check for any loose connections on Saturday as it’s late now. Thanks guys. I must add that this was wired up when I had a new kitchen extension done so I might find it hard to trace exactly where this wire is going and if it’s connected t something else?
     
  11. JayDiy

    JayDiy

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    Oh by the way when you say also test the connection between live and earth, and live and neutral what readings am I supposed to get with the mcb switched on or off, is it the same as checking the voltage across live and neutral, I know silly question but I don’t want fireworks let me know please cheers.
     
  12. Taylortwocities

    Taylortwocities

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    Voltage between L&N and L&E will be more or less the same. Depends on your supply type.
     
  13. EFLImpudence

    EFLImpudence

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    With MCB off, there should be 0V from L out (top) to N and E.

    MCB on, L to N and L to E should both be around 240 V.
     
  14. JayDiy

    JayDiy

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    What about neutral and Earth? I forgot to mention
     
  15. EFLImpudence

    EFLImpudence

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    Might be a couple of volts.

    It depends on several things including your meter.
     
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