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TT On-street EV charging installation, Upstream RCD requirements

Jeff Saunders

Could someone clarify whether a 100mA/300mA upstream RCD is required for an on-street TT EV installation, where all outgoing circuits are 30mA protected within the feeder pillar DB, also if the outcome is different for a metal or GRP feeder pillar?

BS7671 Reg 531.3.5.3.1, and the Code of Practice for EVCE 'On-street', Section 7.4.2.3  both state that an upstream RCD is required, but this seems to be a very contentious among installers.

There are situations described in the OSG where an upstream RCD can be omitted where certain conditions are met, insulated cable entry gland, meter tails of reinforced or double insulation, secured throughout their length to arrest movement etc.

However, special locations are outside the scope of the OSG and I'm wondering if this is where the different opinion originate.

  • +1

    What protective measure is being deployed within the feeder pillar to provide protection against electric shock?

    If it's automatic disconnection of supply, and the earthing arrangement deployed is TT, It's highly likely you will need a suitably rated RCD to supplement the overcurrent protection device at the incoming section. You will also need similar protection upstream to protect against faults that take place inside of the feeder pillar but upstream of the incoming protection device.

    I think it's technically feasible for feeder pillars to utilise the protective measure of double or reinforced insulation. Essentially, all of the wiring, switchgear/controlgear, and the enclosure itself is rated at least Class II, meaning an RCD isn't necessarily required at the incoming section.

  • 0 in reply to Bh

    Thanks for the response,

    It's a couple of different scenarios that I'm looking at.

    Double or reinforced insulation doesn't look to be excluded as an acceptable protective measure in 'on-street' EV installations in the Code of Practice, so a GRP feeder pillar with an insulated DB  and Class II EV equipment would meet this requirement as I understand it.

    But a metal feeder pillar and/or metal DB Class I, would use ADS as the protective measure and in all likelihood would require an upstream, time delayed RCD installed as close as practicable to the service cutout to meet the requirements?

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