Adding a single socket spur

[Andy Burns]

7 miles range per hour of charging seems typical, on a 2.3kW charger.

£8 per day?

[Mark Carver]

Works out (at 15p unit) at 5p per mile.

Anyway, my friend will be paying for the drinks that night in the local boozer.

[Scott]

Are you getting one of these self-driving vehicles :-)

[Robin]

+7 - as in ditto for a 20A for a double socket just in case they want to vac the car while it's charging

[charles]

that's about the same as 24 litres of petrol.

[charles]

currently my car costs about 13p per mile using diesel.

[Andrew]

Plus regular oil and filter changes.

[charles]

indeed, I won't need these in future, but I was simply relating one fuel to another.

[Scott]

At 33 pence per litre.

[John Rumm]

Most plug in chargers limit their draw to around 10A

Yup, that is an option, although offers lease finesse...

The primary requirement would be that the existing circuit has RCD protection at <= 30mA

The downsides are you don't have a way of isolation for the socket, and should a fault occur because of it (say it got damp and started tripping the RCD), you have no discrimination either - so you end up with you indoor circuit being tripped with no way to stop that.

A double pole isolation switch inside would be very well worth having IMHO.

Yup also OK. Since it's juts one socket (be it single or double) then it is treated as a spur, and overload protection for that bit of cable is provided by the limitation in load imposed by the socket, not by the MCB at the origin of the circuit.

Three ought not be a problem. You could wire the additional switch above the existing socket, terminate one of the ring cables in that instead of the existing socket, then run a short extension back to the socket - this including the new switch into the ring rather than wiring it as a spur. You would then have the output cable from the witch running from it's own set of terminals. So no set of terminals would need more than two cable.

Probably not an issue on the terminal side of the socket (if its a double with will be rated for a continuos load of of at least 20A). Overheating is normally a problem on old tired sockets with weak spring contacts, and dirty terminals. With a new socket (protected by a waterproof lid) that ought not be a problem.

[charles]

my mental arithmetic failed: should be 18 litres at £1.33

[ARW]

But can be filled up in less thgan 5 minutes at lots of places around the UK and then do 600 miles with the heatlights, heater, heated rear window or the a/c on full blast.

[ARW]

Unfused spurs off a ring don't.

[ARW]

As long as the socket/cable has RCD protection there is no problem. I have no idea what setup your sparky left you with but I assume both the socket and cable will need RCD protection in your case.

It's a different matter if you get a proper car charger as it sounds like the MCB is sharing a RCD with other circuits. Cross that bridge when you get a an EV and proper charger

[Mark Carver]

Yes, the ring circuit, and the 32A radial are both RCD protected

Yes, it is on the same RCD . Plenty of spare room and capacity in the CU to change that arrangement if/when etc.

I think anyway, as has been suggested by multiple folk, easy (wife operable too) isolation is required, and the best way to achieve that is the suggestion of drilling a hole in the wall under the existing internal socket, and feeding the outdoor socket via a bit of flex with a

13A plug on the end.

I looked at the 32 A 6mm cable in the outside wall box. There's about

350mm coiled up in there. I'm reluctant to trim it down, because if I do it probably won't be long enough for any future EV charger !  So that means fitting the socket next to the box, and it will all look a bit crap.

[Scott]

Which would cost £23.94 per day - hardly about the same as £8.

[charles]

who would need to charge for 24 hours?

[Andy Burns]

Potentially, someone who's come from more than 168 miles away

[Theo]

So am I right in understanding it goes:

Main switch Shared RCD

32A MCB 6mm2 cable External wall box ?

My questions are: what are you isolating, and from what are you isolating it?

If you have a fixed bit of equipment, you want to isolate it if it goes wrong. You also want to isolate cabling etc to work on it.

ISTM that you can isolate the circuit to work on it at the MCB. And the actual external socket has nothing worth isolating in it - it's not an EV charger with electronics, it's just a socket.

So how about a switched socket:

the switch provides isolation of the downstream thing plugged in, and the socket allows it to be easily removed from the circuit.

What I'd do is get another identical wall box and mount the socket on the lid. You'd have to strip a few mm of the existing cable, but that's it. Keep the lid of the old one, and it's very easy to revert back to the setup you currently have. And then when you get an EV charger properly fitted you can just swap the wall box for the charger box.

Alternatively for a neater job you could swap out the wall box for a socket box if you can find one with enough space to coil the spare cable in the back (maybe the double socket versions?). You can also get them with an RCD if you're more paranoid. I don't imagine 6mm2 cable at 10A is going to warm very much so coiling in a confined space probably won't be an issue.

Theo

[ARW]

I think you have got it spot on.