EV Charging RCD

Hi all,

For a 30 kW DC EV charger on a TN-S system, does the RCD need to disconnect the neutral as well?

The supply is 3-phase + neutral.

The proposed RCD monitors all three phases and neutral but disconnects only the three phases, leaving the neutral connected.

My understanding is that, on a TN-S system where the neutral can reliably be considered to be at earth potential, it is not generally necessary to disconnect the neutral.

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0 Chris Pearson 23 hours ago

Why do you need an RCD (RCBO) in the board, as opposed to an MCB?
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0 Gyaneshwar Kumar 22 hours ago in reply to Chris Pearson

I don't think I need a RCD(RCBO) given that the charger has a type B RCBO on the AC side, and DC leakage protection on the DC. However, the charger supplier has advised to still add a type A RCD in the upstream DB supplying the charger which is not clear to me. I am trying to talk to their technical expert and clarify. Thanks for your response.
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0 Gyaneshwar Kumar 22 hours ago in reply to Chris Pearson

I don't think I need a RCD(RCBO) given that the charger has a type B RCBO on the AC side, and DC leakage protection on the DC. However, the charger supplier has advised to still add a type A RCD in the upstream DB supplying the charger which is not clear to me. I am trying to talk to their technical expert and clarify. Thanks for your response.
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0 gkenyon 22 hours ago in reply to Gyaneshwar Kumar

Gyaneshwar Kumar said:
However, the charger supplier has advised to still add a type A RCD in the upstream DB supplying the charger which is not clear to me. I am trying to talk to their technical expert and clarify.

A Type A RCD cannot be installed upstream of a Type B RCD. See Figure A53.2 on page 205 of BS 7671:2018+A4:2026.
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0 Chris Pearson 22 hours ago in reply to Gyaneshwar Kumar

Surely, the only reason to have an RCD in the board is to protect the cable to the EVCP, i.e. additional protection. Since you say that additional protection is not required, I'd install an MCB.

You only have to take account of manufacturers' instructions, not follow them blindly.
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0 Gyaneshwar Kumar 19 hours ago in reply to Chris Pearson

I agree. I have now clarified with their technical expert and they have confimed an RCD is not required in the DB. Thanks!
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EV Charging RCD

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