Sourcing MCB for Legrand CU

Discussion in 'Electricians' Talk' started by Puffer, Apr 12, 2019.

  1. Puffer

    Puffer Member

    I need a 20A B-type MCB to fit an existing Legrand domestic CU. The part number is 06161 but I believe that other Legrand/Tenby MCBs will also fit. However, I'm having little luck in sourcing one, new or used. Can anyone identify any other model or make of MCB that will also fit the Legrand unit?

    The MCB would go at the end of the row, fed from an RCD. Failing proper busbar alignment, is it permissible to feed the alien MCB (or, alternatively, a single-module RCBO) through a wire link to the adjacent MCB/busbar?

    I realise that mixing makes of MCB/RCBO is considered by some to be bad practice but, if the correct item is not available, this may be unavoidable.
  2. Comlec

    Comlec Screwfix Select

    Plenty on eBay
  3. spinlondon

    spinlondon Screwfix Select

  4. Puffer

    Puffer Member

    I found only one 16A that corresponds, and that is used and priced at £12.99! Hence my query about which others (Legrand/Tenby or otherwise) will fit.

    Thanks for that info. I'm nowhere near Harlow, but what outlet please? Likewise, no Denmans near me but I will check with them on compatibility.

    I'm now favouring use of an RCBO rather than an MCB in the existing CU, as that would usefully give protection to the new circuit independent of the existing RCD circuits. If the busbar will not fit into whatever RCBO I can install, is there any good reason why it should not have its live feed by means of a wire link from the main switch instead?
  5. JP.

    JP. Screwfix Select

    ''I can install, is there any good reason why it should not have its live feed by means of a wire link from the main switch instead?''

    No I would not have thought so tbqh Puffer - maybe I;m wrong, but it doesn't sound like cricket to me
  6. peter palmer

    peter palmer Super Member

    You say that but I had to do that very thing the other day. I needed a dedicated supply to a fire alarm panel and the board that had been fitted was a new 10 way Schneider one that only had 4 circuits connected in it. So it was either use one of the many spare ways or install a 1 way unit involving henley blocks etc.

    Normally you can fit an MCB next to the main switch and use a 1 way bus bar to link them together making an unprotected circuit but due to the daft way the Schneider boards are made up the live is on the right and the neutral next to the MCB's/RCD's. So I fitted the MCB on the far left and linked it to the bottom of the main switch with a bit of 10mm, Bizarrely there was an unprotected neutral bar. Not exactly type tested but I'm sure it will be reet.

    Incidentally this type of board, formally square D is the only board I've ever ended up tailing in backwards, truly is a bizarre way to make a mains unit.

    Edit : I was trying to find a picture of what I meant and when I saw one I realised what I should have done instead, I should have disconnected the first RCD of the bus bar link and moved it one space to the left then put the MCB there instead and then used a 1 way bus bar to link the RCD to the MCB. This would have thrown all the labelling out on the cover though.

    At least I'm in before the smart arses telling me I've done it all wrong.
    Last edited: Apr 13, 2019
  7. peter palmer

    peter palmer Super Member

    Looking at this picture it looks like the bus bar comes with a couple of unprotected ways on it, the one I worked on obviously had already been cut down.


    You live and learn.
  8. spinlondon

    spinlondon Screwfix Select

    Sam’s trade centre.
  9. Puffer

    Puffer Member

    I went to Sam's Trade Centre (Harlow). The MCBs there are not Legrand but clearly by Lewden, although branded as 'Dencon', and cheap at £1.99 each + VAT. As it happens, I had bought a Lewden RCBO elsewhere and this is what I fittted to the Legrand board, connecting it directly to the main switch by a wire link. (The Lewden items take a busbar at a slightly different position to the Legrand, but close enough that I'm sure a good fit would be achieved by a slight tweak if Legrand/Lewden were fitted adjacent.)

    I'm still curious about alternative MCBs that are physically compatible with Legrand/Tenby. (Steeple was mentioned above but I haven't inspected one.)
  10. spinlondon

    spinlondon Screwfix Select

    Sorry, I must have got Lewden and LeGrand mixed up.
    CEF stock LeGrand MCBs.

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