Addition of a new circuit............

In the wake of the new webinar on inspection and testing, is it still compliant to add a new circuit to an existing plastic consumer unit fitted with type A/C RCD protection and nothing else?

How much 'engineering judgement' leeway do I actually have?

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    The first impression of that consumer unit is it is better than most, but actually it’s just a six year old dual RCD consumer unit with two Type AC RCDs, however all replacement devices are available for it, so to install a new circuit for EVSE do we alter and upgrade the existing consumer unit or turn the supply off at the DNO isolation switch in the external meter box, cut the tails then install an additional consumer unit?

    https://m2electrical.co.uk/

  • My option would be to install a new dedicated consumer unit for the E.V. charger. I think that the existing consumer unit main switch has enough work to do with all of those existing final circuits as is.

    Z.

  • I know next to nothing about EV chargers or the technology they employ so educate me.

    Is there 230VAC present in the lead between the car and the charger? Or is it just simple whatever-volt D.C. with a couple of comms links to monitor battery charge? If 230VAC is present, then I understand the need for a charger-based RCD.

    Also, what is inside the charger which can send a blinding D.C. current back up your supply cable to your consumer unit? And what could be done to prevent it?

  • Is there 230VAC present in the lead between the car and the charger? Or is it just simple whatever-volt D.C. with a couple of comms links to monitor battery charge? If 230VAC is present, then I understand the need for a charger-based RCD.

    In AC charging systems (Modes 1, 2 and 3 - although mode 1 is no longer found with new vehicles, and Mode 2 is the "granny lead") there is 230 V single-phase or 400 V three-phase switched to the vehicle, direct from the electrical  installation - in Modes 2 and 3, provided safety criteria are met, and for Mode 3, provided pilot comms is established.

    Also, what is inside the charger which can send a blinding D.C. current back up your supply cable to your consumer unit?

    The comms, that is transmitted out on CP and back through PE, is either steady or pulsed DC.

    In TN systems, particularly TN-C-S, with Mode 3 charging, it's easy to demonstrate that N-PE fault between the EVSE and the vehicle could cause the pilot signal to share between N and PE, and this would then put a sufficient amount of DC on the Neutral of the RCD such that some Types of RCD are affected.

    And what could be done to prevent it?

    Nothing without changing the charging standards for EVs - which will do absolutely nothing for the vehicles and chargers out there already.

  • Graham,

    Thank you for your reply. I found it most interesting. Many thanks once again for taking the time and trouble.

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