Replacing MCB's with RCBO's

Discussion in 'Electricians' Talk' started by diymostthings, Sep 28, 2015.

  1. diymostthings

    diymostthings Well-Known Member

    Hi

    Is there any objection to replacing MCB's which are already protected by an RCD by RCBO's? If allowed, I'm hoping the RCBO would trip out before the RCD, so only the RCBO circuiit becomes "dead"

    Kind regards

    diymostthings
     
  2. Jitender

    Jitender Screwfix Select

    What type of board is this, is it a dual RCD (split load board)?
     
  3. stu1312

    stu1312 Member

    It will be a total gamble which trips out first on each circuit to be honest and if you have any slight earth leakage on the other circuits most likely it will be the main rcd due to a cumulative effect of all the earth leakage going through it.
     
  4. diymostthings

    diymostthings Well-Known Member

    It's an MK 17th edition split load with two RCD's covering all circuits except 2 which are only protected by an MCB
     
  5. diymostthings

    diymostthings Well-Known Member

    Hmmm. That's what I feared stu312. Is there ANY advantage then in doing this?

    kind regards

    diymostthings
     
  6. retiredsparks

    retiredsparks Super Member

    DIY, what is the reason behind your proposed change ?
    RS
     
  7. diymostthings

    diymostthings Well-Known Member

     
  8. diymostthings

    diymostthings Well-Known Member

    Well although I have split the circuits controlled by the two separate RCD's as recommended it is still inconvenient to have several circuits tripping out when only one is faulty - and it could be any one of the 5 circuits controlled by that RCD which is the faulty one. With an RCBO on each, you would know which circuit is faulty and only that one would trip. So the idea was by way of an upgrade but I wasn't sure if it was practical to buy expensive RCBO's only to find out that the RCD trips anyway. Hence my question.

    Is there a solution?

    kind regards

    diymostthings
     
  9. Coloumb

    Coloumb Screwfix Select

    Are you currently having problems with the rcd's tripping out? Might be best to get a spark in to trace the fault if you are. I've been using a split load boards for years now and not had any problems.
     
  10. Gazza999

    Gazza999 New Member

    Was it sold to you as a "High integ dual RCD board" if so there should be 3 neutral bars 1 for each RCD and 1 for the unprotected High integ circuits on which you currently have MCBs. Replacing the MCBs with RCBOs is pefectley standard practice that is often done on installations for ccts like freezers or problem tripping cookers, these RCBOs would be on the seperate neutral bars and should not interfere with the RCD ccts. However as already stated if you have problem tripping then you need a spark to trace the fault as it may not be on the RCD that it appears to be.
     
  11. sinewave

    sinewave Screwfix Select

    Pointless and expensive exercise!

    If sumats tripping get it looked at by a Pro
     
  12. bonkrs24seven

    bonkrs24seven New Member

    Hi folks, I have just bought a Wylex box complete with eight RCBs, to my horror they were those new fangled Wylex NHXSBS1Bs with the white and blue wires sticking out the top!! Does anyone know where they need to be wired to? Thanks
     
  13. peter palmer

    peter palmer Screwfix Select

    Yes I do but you obviously don't so tough.
     
    sparky Si-Fi likes this.
  14. spinlondon

    spinlondon Screwfix Select

    White is functional earth, blue is neutral.
    The circuit neutral is wired into the RCBO, and the neutral from the RCBO connected to the neutral bar.
     
  15. bonkrs24seven

    bonkrs24seven New Member

     
  16. bonkrs24seven

    bonkrs24seven New Member

    Hi thanks for that, I had tried wiring the white to the earth bar and blue to the neutral bar but it tripped as soon as power was required.
     
  17. diymostthings

    diymostthings Well-Known Member

    No problems with tripping Coloumb - just thinking ahead to "if and when" a fault occurs.
     
  18. diymostthings

    diymostthings Well-Known Member

    Yes it is a Wylex dual RCD board - and I completely understand the earthing busbar requirments. i have no tripping problems - just thinking ahead...
     
  19. diymostthings

    diymostthings Well-Known Member

    No tripping sinewave - and I have the gear needed to measure Zs and to trace faults. It was a TT to TN-C-S (PME) conversion. I was just thinking ahead to the day when something goes wrong...

    diymostthings
     
  20. spinlondon

    spinlondon Screwfix Select

    Did you connect the circuit Neutral to the RCBO?
     

Share This Page

  1. This site uses cookies to help personalise content, tailor your experience and to keep you logged in if you register.
    By continuing to use this site, you are consenting to our use of cookies.
    Dismiss Notice