EV charger considerations on TT supply

DaveS · Dec 11, 2021

Hi all. Will have to forgive me for enquiring about basic question but would rather be sure of all considerations than not. Went to view property for potential EV install yesterday. On viewing intake of property I realised supply had been converted from PME to a TT supply. I'm unsure why they may of done this? The property does have solar power, could this possibly have been a consideration why they converted this?

The whole install is protected upstream with 100ma RCD then to household dual RCD board. I took a quick ZS reading at intake and was 100ohms which is acceptable to me. My plan for EV as will be situated conveniently next to outdoor intake cupboard will be to split supply from 100 amp connector and from here take new supply tails to new dedicated EV A type RCD consumer unit and take my main earth from main earth block. In this situation there will be no 100ma upfront RCD. As not great deal of experience regarding TT installs just wondered if anyone thinks I'm missing any considerations here?

Thanks

mattg4321 · Dec 11, 2021

Any exposed/extraneous conductive parts connected to PME in adjacent property nearby?

24EMan · Jan 13, 2022

HI DaveS, I see you didn't get much response on this but one comment think worth raising for future readers is the suitability of a the A Type RCD on a vehicle charging point circuit. In general the potential for DC Leakage/DC fault current may command at least a type AC or type B. Section 722 applies stating "at least Type A" but primarily requirements as stated by the manufacturer of the EV equipment should be followed. Does the particular EV charging equipment have protective measures against DC Fault Current? Type A probably doesn't cut it on DC equipment downstream and would be at risk of leaving the circuit without any effective RCD protection. I think the jury is still out and amendments being considered on DC connections.

As far as no upstream RCD on the supply, my current understanding would be I don't think this is an issue providing considerations to protect the meter tails are being met. Would welcome hearing from those most experienced in TT installations.