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RCD Protection for Commercial EV Chargers

Daniel McNeill

Do we need RCD protection at the source (Main LV Panel) for commercial EV Chargers? For example if we are feeding a 180kW 280A EV Charger from a main LV panel, does the supply AC cable need to be protected by an RCD? I do not personally think this is clear from the IET Code of Practice for Electric Vehicle Charging Equipment Installation, which seems to be more related to domestic installations.

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    If the charging point (i.e. outlet to vehicle) is AC, then BS 7671 requires the individual charging point to be protected by an RCD with residual current rating not exceeding 30 mA, that disconnects all live conductors.

    However, I'm guessing with the power, you're looking at a Mode 4 (DC output) charger.

    If the charging point is DC, then the RCD can't, of course, be fitted on the DC side. However, if the charging point is DC and there is no separation between AC and DC, the IET CoP recommends RCD is provided on the AC side according to 722.531.3.101. See Annex K, 3rd para of K2  for DC chargers witihout separation (page 158), and Annex K, 3rd para of K3 for DC chargers with separation (again, page 158). However, RCD may be required for Mode 4 EVSE having separation, in order to provide ADS for the AC side of the internals of the charging point, where the PE is separated at the charger having electrical separation, for AC supplies in PME systems (to avoid one of the options in 722.411.4.1) - see Figure K.2 on page 159 of 4th Ed CoP.

    RCDs may be required for AC circuits other purposes, which might include, for example:

    • ADS in TT installations
    • additional protection for other reasons, e.g. requirements of other special locations requirements depending on the particular installation
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    If the charging point (i.e. outlet to vehicle) is AC, then BS 7671 requires the individual charging point to be protected by an RCD with residual current rating not exceeding 30 mA, that disconnects all live conductors.

    However, I'm guessing with the power, you're looking at a Mode 4 (DC output) charger.

    If the charging point is DC, then the RCD can't, of course, be fitted on the DC side. However, if the charging point is DC and there is no separation between AC and DC, the IET CoP recommends RCD is provided on the AC side according to 722.531.3.101. See Annex K, 3rd para of K2  for DC chargers witihout separation (page 158), and Annex K, 3rd para of K3 for DC chargers with separation (again, page 158). However, RCD may be required for Mode 4 EVSE having separation, in order to provide ADS for the AC side of the internals of the charging point, where the PE is separated at the charger having electrical separation, for AC supplies in PME systems (to avoid one of the options in 722.411.4.1) - see Figure K.2 on page 159 of 4th Ed CoP.

    RCDs may be required for AC circuits other purposes, which might include, for example:

    • ADS in TT installations
    • additional protection for other reasons, e.g. requirements of other special locations requirements depending on the particular installation
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