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Regulation stating a type AC RCD can not be upstream from a type A RCD

Alan B

Hi

I found an EV charger today with built in type A RCD + RDC-DD connected to a type AC RCD in the consumer unit, the AC RCD is also protecting 3 other circuits including sockets. I know this is incorrect because the type AC RCD could be blinded by DC currents, but I am struggling to find a regulation to reference when providing information to the customer?

Thanks

Alan

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  • 0

    Hi Guys, Im new to the Forum but I hope this information can help Which I found earlier. 

    Selectivity of RCD types - Wiring and the Regulations BS 7671 - IET EngX - IET EngX (theiet.org)

    Also Look at regulation 722.531.3.101

    Also Regulation 314.1 is all about selectivity and Poor discrimination this is the only regulation I think that applies to your question. 

    If the downstream device and upstream are both rated at 30ma then in my opinion can cause an issue. 

    If there is AC leakage in the type A or AC then one or the other or both can trip. Either by Fault of Nuisance tripping. 

    if the Unit is supplied by SWA and the Zs is within permitted Values for an MCB device then RCD protection is not needed on that circuit but the Devices inside the Charger will have to be a Type A RCD and a RDC-DD and will have to disconnect all live conductors and disconnect power from the outlet. 

    All of the above is just my opinion and interpretation 

    What does everyone else think ? 

    Yassir

  • 0 in reply to Yassir Khalil

    Agreed. Its supplied on an SWA cable. The best solution would be to use a non RCD protected feed from the DB, but that would mean a significant re organisation of the DB or an additional DB. This was installed by another company, I am recommending the customer goes back to the original installer and asks them to replace the RCD. This is going to cause enough problems, trying to force them to correct the selectivity issue as well is going to cause a big fight.

    I have informed the customer that ideally the charger should be on it's own non RCD protected output from the DB or additional DB but it would be ok to just replace the type AC RCD with a type AC. 

Reply
  • 0 in reply to Yassir Khalil

    Agreed. Its supplied on an SWA cable. The best solution would be to use a non RCD protected feed from the DB, but that would mean a significant re organisation of the DB or an additional DB. This was installed by another company, I am recommending the customer goes back to the original installer and asks them to replace the RCD. This is going to cause enough problems, trying to force them to correct the selectivity issue as well is going to cause a big fight.

    I have informed the customer that ideally the charger should be on it's own non RCD protected output from the DB or additional DB but it would be ok to just replace the type AC RCD with a type AC. 

Children
  • 0 in reply to Alan B

    If it a high integrity DB then insert a MCB next to the main switch if possible, The customer could request that I guess 

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