Replace RCCB for something else?

Discussion in 'Electricians' Talk' started by Axbridge, Jan 13, 2017.

  1. Axbridge

    Axbridge New Member

    To explain, from the meter we have one CU, this then feeds a separate RCCB (63A) which then feeds another CU for a large extension (housed in the extension). I believe there's a 10m run of 16mm2 cable running to the extension.

    During our frequent power cuts (rural) once power is restored, the only item to trip is the RCCB, which in turn knocks out power to the CU for the extension, where the freezer and other important items live.

    This only happens after power cuts and has happened since the installation a couple of years ago.

    Having read up on nuisance tripping of RCCBs, I was wondering if it's possible to switch it out to something other than an RCCB in this instance and let the CU deal with any issues. This would leave the 10m run of cable un-protected I guess, not sure how the sparky wired the RCCB to the main CU to know for sure on that.

    The CU that it feeds has a 100A switch and twin 63A RCCBs.

    Just a thought, open to suggestions.
     
  2. FatHands

    FatHands Well-Known Member

    Would help if you could upload some photos of what you have, but dont go removing anything - you need an electrician on site to assess what is required.
    Perhaps you have a TT type of earthing system with a time delayed upfront rcd in the first consumer unit?

    Edit:
    Forgot to say have you reported your power losses to your dno?
    You can find out who it is here:
    http://www.energynetworks.org/info/faqs/who-is-my-network-operator.html
     
    Last edited: Jan 14, 2017
    Joe95 likes this.
  3. nigel willson

    nigel willson Screwfix Select

    As I read it. You've got a front end rccb (rcd) feeding a submain, with splitload board other end?
    If that's the case and you don't have TT earthing? Then you could remove rccb, change for switchfuse.change board at far end for one with Rcbos.but you need to get a sparks round to advise
     
  4. Axbridge

    Axbridge New Member

    I'll just get an electrician round then as it doesn't sounds as simple as I had hoped.

    Fats, we're in the sticks, everyone gets power cuts unfortunately, part of every week life here.

    Nigel, I don't fancy swapping out 9 MCBs for RCBOs, pricey solution isn't it?

    Cheers though fellas, I'll get someone out to take a look and see what they recommend. If it's a simple solution I'll post back with an answer (if I remember) as I hate coming across threads where the OP disappears :)
     
  5. Pollowick

    Pollowick Screwfix Select

    When the electrician is there you need to find out if te cable to the extension can be upgraded to SWA.

    Rather than change all MCBs to RCBOs you could ask about installing one or two additional circuits with their own RCBOs to provide power for the freezer and other items.
     
  6. Axbridge

    Axbridge New Member

    With all due respect, the cable won't be switched to SWA, it's all internal, and what would the point in changing the (sorry, adding) additional circuits for a freezer on an RCBO when the RCCB 10m before this CU is the item tripping. Wouldn't make any difference would it?
     
  7. nigel willson

    nigel willson Screwfix Select

    Like we said we can't give you a correct answer without seeing the setup! It's complicated I know but that's electrickery for u
     
  8. Axbridge

    Axbridge New Member

    I've just taken some photos to help people visualise.

    From the meter, two sets of tails, one feeding the CU in the top of this picture, the other set feed the one on the bottom on the left. Ignore the 2.5mm2 running back up to the top CU, I have no idea what he's done there, I'll pop the lid off and take a look at some point, but it's a red herring.

    Linked images, sorry, this place doesn't like the links embedded - or I'm doing it wrong.

    https://goo.gl/photos/wxbCNWuCZZzV433Y9

    The RCCB in the lower right is being fed from the lower CU - and that CU deals purely with the heat pumps, used to do one of the outbuildings too, but that's been switched back to an RCBO on the upper CU (which is probably what the twin and earth going between the two is for actually).

    https://goo.gl/photos/G8Qauf5xzziP7V4R6

    The RCCB pictured above runs 10m or so (internally, sorry to Pollowick, I didn't make that clear before) to the CU pictured below.
     
  9. Axbridge

    Axbridge New Member

    Should the 63A RCCB be that size? Could the immediate draw after power is restored be tripping it because it's incorrectly sized?
     
  10. nigel willson

    nigel willson Screwfix Select

    NO!!!
     
  11. nigel willson

    nigel willson Screwfix Select

    It goes out on current imbalance not load draw.
     
  12. All in all it looks like you have a pretty rough installation looking at the photos.
    Has he piggy backed the supply for the RCCB from the 80a RCD mainswitch in the consumer unit.
    The best idea would be to get an Electrician in to sort it out.
     
  13. Axbridge

    Axbridge New Member

    Yes, this seems to be what happens when I get an electrician out. So far I've had a loose live in a rotary switch outside, an improperly sized CU for a workshop and now this.

    I'll try another one then. From another body this time. Tried reporting the last one to NICEIC, they weren't remotely interested.

    Cheers for the help.

    And Nigel, calm down yeah? It was just a question.
     
  14. tina lucinda lane

    tina lucinda lane Screwfix Select

    needs a latching rcd (or rccb or whatever other name you want to give it) as what is installed at the moment is non latching (put simple latching models do not trip when power cuts where as non latching do trip when power is cut)
     
  15. unphased

    unphased Screwfix Select

    IMHO, the problems you are experiencing are due to inappropriate use of dual RCD CUs. Those CUs are sold by Denmans. You would do far worse than getting rid of all the RCCBs and just putting main switches in, then changing ALL the circuits to RCBOs. You can get RCBOs for those boards for around £15 each and although it sounds expensive you will not have issues with powercuts causing you loss of power on switch on. Best advice is get an electrician who knows what they are doing! There are so many who "blag" and aint got a clue. If I was living near you I would gladly come out and advise. I'm Tamworth if that helps. That's just a generalised response btw and there are other factors to consider but are easily determined on site.
     
  16. Axbridge

    Axbridge New Member

    Food for thought, I'll take all that on board and see what level of muppet I end up with.
     

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