RCD or Circuit Breaker

Discussion in 'Electricians' Talk' started by PHILPH, Dec 20, 2020.


    PHILPH Member

    Could I ask some advice please.

    The electricity has went off in the kitchen while the wife was cooking dinner however just before it happened there was a crackling from the fuse box. The whole house electrics went off however I reset the box apart from one of the circuit breakers wouldn’t push up and lock so Im assuming it’s knackered.

    I’ve plugged the fridge freezer into an extension lead just for now until I can get out and buy a new breaker therefore my question is what am I replacing?

    How can I tell the difference between an RCD and circuit breaker?
  2. Bogle Crag

    Bogle Crag Screwfix Select

    RCD/RCBOs have a test button
  3. jonathanc

    jonathanc Screwfix Select

    I don’t wish to offend but if you are not sure what you are replacing do you feel competent to do the replacement? Also to diagnose what the cause of the problem is?

    you’ve got to be mighty careful opening up a CU !
    seneca likes this.
  4. terrymac

    terrymac Screwfix Select

    Breakers trip for a reason. Show pics of your consumer unit . With the main isolator switched off ,does the breaker in question then set ?

    PHILPH Member


    It’s a Hagar fusebox and the breaker has the following printed on it.

    MT 132 and also B6

    It also has the numbers 450132

    If I can find one I’ll get a spark in to wire it up unless its a simple job?


    Attached Files:

  6. Teki

    Teki Screwfix Select

    You do realise by installing an inferior Chint MCB in a Hager CU, you've invalidated the type approval.
  7. terrymac

    terrymac Screwfix Select

    Your asking for advice Phil ,but not answering our questions doesn't give us much chance . A picture of the consumer unit in full would have been useful ,not just a few breakers ,which are MCB's by the way.
  8. Sparkielev

    Sparkielev Screwfix Select

    That bus bar cant be fixed right due to the chnt mcb, probably the cause of your issues, for the sake of a couple of pound somebody has done a bodge
    Teki likes this.

    PHILPH Member


    New photo attached,

    Tiki....are you saying the whole box looks dodgy?

    If so I would be quite happy to get a new one installed.

    Does anyone think it would be better just to renew?

  10. Teki

    Teki Screwfix Select

    Hager is a good brand however, by installing a cheap Chint MCB for the sake of a couple of £s as @Sparkielev mentioned, it may have created problems.
  11. PHILPH

    PHILPH Member


    It would help if I attached the photo!
  12. PHILPH

    PHILPH Member

    Photo attached.

    Sorry I forgot to add it, I’m having a bad day!

    Attached Files:

  13. Teki

    Teki Screwfix Select

    You have a single RCD protecting all the circuits. So an earth leakage fault on any circuit would take out the entire house. One option that is costly would be to upgrade the consumer unit to RCBOs (combined RCD and MCB) for each circuit.

    Was dinner being cooked in an oven?
  14. PHILPH

    PHILPH Member

    Luckily dinner was just about done however she who must be obeyed wasn’t too pleased (is if I could do anything about it!)

    I believe the oven has a separate supply and it’s only the sockets not working in the kitchen.

    Really grateful for the help, however could I clarify what I need tomorrow.

    A 32 amp MCB?

    Regarding this cheap
  15. PHILPH

    PHILPH Member

    Damn, I’m off again!

    Sent the last reply before I finished!

    What I meant to add was regarding the cheap Chint MCB, what do I need to replace this?

  16. terrymac

    terrymac Screwfix Select

    You may not need a new MCB. They trip for a reason ,and you need to establish what the fault is .
    The chint MCB has nothing to do with the one that tripped ,but is wise to replace it with the correct Hager model.
  17. PHILPH

    PHILPH Member

    Thanks again for the advice guys, sounds like it may not be as straight forward as first thought so it looks as though it’s a job for a spark.

    I’ll try and get one out tomorrow.

  18. PHILPH

    PHILPH Member

    Just to update.

    Got a spark and he said it was the MCB.

    Got it replaced and also the Chint MCB so all is sorted........touch wood!

    Thanks again for the original replies and Merry Christmas to you all.

  19. MGW

    MGW Screwfix Select

    PartID_CU.jpg The RCD and Isolator are two module width, and the RCD has a test button, the RCBO (which is a MCB and RCD combined) is one module width with a test button, the MCB looks very similar without test button.

    Normal reason for will not reset is there is still a fault, if when you turn off the isolator the unit will reset, and then it trips when isolator is turned back on, then likely there is still a fault, if it will not switch on with isolator off, then likely the RCBO/MCB is faulty, although could still be a fault on insulation as well.

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