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Dual RCD boards are unlikely to be suitable for EV charging installations even with type A or B RCDs, discuss

IronFreely

I’ll paraphrase Regulation 722.531.3.101, “each charging point shall be protected individually by an RCD”. With that in mind a dual RCD board where both RCDs protect multiple circuits will not be suitable as the requirement is for the charge point to be individually protected. The reason I open this up to discussion is because so many installers seem completely unaware of the wording of 722.531.3.101 as about 50% of the installations I see the charger is protected by an RCD protecting multiple circuits, in particular new builds were the provision for electric vehicle charging has been made during development. I also often give quotations to prospective clients where they’ve already had at least one quotation where the previous installer has said “great you’ve got a spare way in your dual RCD board, so we can use that” and I’m thinking “erm no you can’t”

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  • I completely agree. In a presentation IET or NAPIT someone said that DC leakage comes mainly from the EV and not the EV charger point, therefore not fixed. They also said that in tests at least one model of car was found to have 5mA of DC leakage (all from memory so excuse errors).

    If the 5mA of DC leakage is added to say another 3mA from other circuits, or quite commonly now days a second EV on a granny charger the total is well over 6mA as potentially the RCD is blinded.

    Napit covered the subject in a 10 most common questions video Jan 2023 and said we can not have an EVCP sharing an RCD with other circuits. They have clouded the sittuation by taking the opposite position prior to Jan 2023 and apparently the technical help line is still giving wolly answers.

    As far as I can see given the model of EV connected to the charge point is unknown. There will be socket circuits and led lighting on the other circuits, which will have varying loads connected. Overall there is no way of being at all sure that the cumulative DC leakage will stay below 6mA.

    Personally I think NAPIT, NICEIC etc need to take a firm line and stop bowing to pressure from developers etc.

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  • I completely agree. In a presentation IET or NAPIT someone said that DC leakage comes mainly from the EV and not the EV charger point, therefore not fixed. They also said that in tests at least one model of car was found to have 5mA of DC leakage (all from memory so excuse errors).

    If the 5mA of DC leakage is added to say another 3mA from other circuits, or quite commonly now days a second EV on a granny charger the total is well over 6mA as potentially the RCD is blinded.

    Napit covered the subject in a 10 most common questions video Jan 2023 and said we can not have an EVCP sharing an RCD with other circuits. They have clouded the sittuation by taking the opposite position prior to Jan 2023 and apparently the technical help line is still giving wolly answers.

    As far as I can see given the model of EV connected to the charge point is unknown. There will be socket circuits and led lighting on the other circuits, which will have varying loads connected. Overall there is no way of being at all sure that the cumulative DC leakage will stay below 6mA.

    Personally I think NAPIT, NICEIC etc need to take a firm line and stop bowing to pressure from developers etc.

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  • in reply to Alan B
    Alan B said:
    In a presentation IET or NAPIT someone said that DC leakage comes mainly from the EV and not the EV charger point,

    The main DC issue is to do with the pilot communication in the main ... an N-E fault will "blind" RCDs because of this functionality.

    It's not necessarily the EV - it's the standard by which EVs handshake with char "charger" (correctly Electric Vehicle Supply Equipment, EVSE), or with a Mode 2 charging lead, the In-Cable Control Box (ICCB).

    I'm not saying that potential faults within the vehicle itself, downstream of electronics, or due to switch-mode type operation, couldn't cause DC leakage current, just that there's a definite issue with the whole way that the pilot function in the BS EN IEC 61851 series of standards works, that makes DC residual currents an issue, even if you were to make the perfect "no DC leakage" electronic power converter in the on-board charger in the vehicle.

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