MCB tripping RCD

Discussion in 'Electricians' Talk' started by JaySean, Sep 12, 2019.

  1. JaySean

    JaySean New Member

    Installed a Memera2000 B6 MCB (used) into Memera2000 CU. Only thing connected to it is a BG bell transformer ( which connects to a Google NEST Hello. When you turn on the B6 MCB, it trips the 100a RCD that is protecting the sockets and cooker. Upstairs/Downstairs/Smoke Detector and Water Heater MCBs all remain on. Transformer has been replaced so I know that’s not the problem. Nest wire is not connected so that is not the problem either.

    Cable from MCB to Transformer is a 1.5mm2, not sure where I should put the earth on the transformer side though so att the moment I have got the earth connected to a 2-lever Wago Connector. Transformer is housed in a Wylex DIN enclosure (

    Anyone have any ideas of what I should try next?

    Also, would a Eaton B6 MCB or Eaton C6 MCB be compatible with the Memera 2000 CU ( Is it okay to have 1 type C MCB in the CU when the rest are type B?

    Apologies, I am a DIY electricians, trying to educate myself.

    Attached Files:

    • CU.JPG
      File size:
      1.1 MB
  2. Have you put the Neutral in the correct Neutral bar?
    The Neutral should be in the same bar as the Neutrals for the circuits on the Main Switch side of the Consumer Unit.
  3. JaySean

    JaySean New Member

    Hi Deleted member 11267

    Thanks for the quick reply. I think its in the correct neutral bar, but will need to double-check. If it is in the correct side, what else would you suggest?
  4. seneca

    seneca Screwfix Select

    That's the only thing I can think of Jay.
    Deleted member 11267 likes this.
  5. Philip Hyde

    Philip Hyde Screwfix Select

    Yeah that would be my guess. Neutral wrong side. Common mistake.
  6. JaySean

    JaySean New Member

    Thanks guys, you were correct. Traced where the other MCBs were going on the unprotected side and was going to a different neutral bar. Connected to this one and no tripping...hooray .

    Tested the Google Nest and it’s working too.

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