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Replace MCB with RCBO's

Discussion in 'Electrics UK' started by Licklieder, 4 May 2021.

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  1. Licklieder

    Licklieder

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    Hi Guys.

    I’ve got a 12 way Volex 17th Edition split consumer unit that currently has 4 MCB no RCD (for electrical heating) and 5 MCB with RCD protection for lights, immersion, Oven / Hob, Final Ring, & radial socket.

    upload_2021-5-4_15-34-48.jpeg

    There’s a guy on ebay selling New Old stock Volex RCBOS’ of the right type (RCBO function AC & pulsing DC, MCB function – Type B: https://bit.ly/2PRx1m6 ) & ratings, so I was considering replacing the current set of MCB’ with RCBO’s.

    I have a Fluke 1653B multifunction tester so would perform continuity, IR and trip time / current testing before and after the replacement, and will source a torque screwdriver to ensure everything is done up correctly.

    Is there anything else I should be considering ? Aside from updating the labeling when done.

    M.
     
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  3. blup

    blup

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    I think the type AC doesn't have the dc pulsing function.

    Blup
     
  4. AndyPRK

    AndyPRK

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    That brand are type A rcd for DC.

    Often ppl don’t like Rcd for heating, as you can get false trips.
     
  5. JohnW2

    JohnW2

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    What sort of 'heating', and why (why the 'false trips')?

    Kind Regards, John
     
  6. AndyPRK

    AndyPRK

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    Storage heaters. And water absorbation
     
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  7. JohnW2

    JohnW2

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    Interesting. I wasn't aware of that.

    Kind Regards, John
     
  8. EFLImpudence

    EFLImpudence

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    Storage heater elements are not earthed, are they?
     
  9. JohnD

    JohnD

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    I think they are.

    Can't be bothered to go and look at one, though.

    They have a metal sheathing. If the element were to be damaged or burn through, it could become live.
     
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  11. EFLImpudence

    EFLImpudence

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    That's good enough.

    Maybe you should.
    https://www.google.com/search?q=storage+heater+elements'&sxsrf=ALeKk00iIA9QmD8vHR0rAd04QtWpm-sFAQ:1620144458285&source=lnms&tbm=isch&sa=X&ved=2ahUKEwinxq63tLDwAhXOgVwKHRD_CYwQ_AUoAXoECAEQAw&biw=1559&bih=761

    They are inside the bricks.
    MCB?
     
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  12. Licklieder

    Licklieder

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    it's hard to make out from the photos on ebay, but when i zoom in, they do look like type A to me:

    upload_2021-5-4_17-37-21.png
     
  13. Licklieder

    Licklieder

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    I'll bear in mind the possibility for nuisance tripping on heating circuits and keep hold of the exsting MCB's just in case. At the moment, i have cheapo convection heaters fitted but intend to replace them with some nicer electric - wet style heaters in due course. Guess that explains why the spark who fitted my consumer unit way back when split those circuits off from the RCD.

    That said, I have come across some manufacturers of radiator elements who specify the use RCBO's.
     
  14. JohnW2

    JohnW2

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    Indeed, I don't think there is any doubt (and that would correspond with the description to OP posted) ...
    upload_2021-5-4_18-3-3.png

    Kind Regards, John
     
  15. AndyPRK

    AndyPRK

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    How do you turn the heaters on and off ?

    is there a central timer ?
     
  16. crystal ball

    crystal ball

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    Correct they sit inside the bricks, no contact with earth
     
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  17. Licklieder

    Licklieder

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    As per the original late 60's / early 70's install Each room has it's own thermostat. There used to be a central timer / relay box but i too that out when i replaced the old mechanical thermostats with Aube Th132's digital onse which work well for temp control / disabling the heaters with the 'holiday' function. Each heater is connected to the circuit via it's own FCU.

    A project for another day will be to add appropriate isolation switches before the thermostats as the installation pre-dates that requirement.
     
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