Yep - that's nonsense.
An EV Charger doesn't take charge from an existing ring main.
I said their
supply, not a ring main, nor or any other particular circuit.
The suggestion is that their 100 amp single phase supply is too near capacity to supply the additional 30ish amps for a 7kW EV charger.
That is theoretically possible, because an induction hob range cooker (40 amps), their hot tub (32 amps) and an electric shower (30amps) together would exceed the supply already, without considering lights, other appliances and maybe a heated towel rail or underfloor heating mat, or the kids on their Playstations.
But that's a peak daytime demand scenario that is extermely unlikely to occur at night, so simple timers would avoid that overload sceanario, and some degree of smart monitoring of supply & demand would avoid any risk anyway. I assume there are smart chargers that can do this.
Edit to add - slight cross post with Andy - I was in a meeting and hadn't seen his contribution. He refers to clamp meter on the meter tails to monitor the overall supply to a house. THat's exactly the solution that would address the problem my friends report.
Even if you are drawing from a 3 pin plug, the car will adjust what it takes based on the available output from the socket without tripping the fuse box.
I suggest a car charging from 13amp sockets has absolutely ZERO idea what the "available output from the socket" might be, and just assumes 13 amps is available all the time. IT's a fairly safe assumption, as house electrics have a reasonable margin of error to cope with overloads.
To do what you suggest, you'd have to tell the car the fuse/MCB/RCBO rating, and also install clamp sensors on one or more conductors in the consumer unit for an individual circuit. V unlikely.
Unless I'm missing something. I've not done electrician work since going into IT 3 decades ago.
