Pre-Emptive Wiring for future EV charger

[Sard]

I did ask this in another similar themed thread but I thought I'd create a dedicated thread for this.

I'm trying to future proof as much as possible whilst I'm renovating my house and see myself switching to a plug-in car at some point in the next 2-3 years. However, I would like to avoid running a cable around the exterior of the house as my meter and CU are on the opposite side to where driveway is. Therefore I'm thinking if I could pre-emptively lay a cable from my CU, through my floorboards (see attached) to where the EV charger would be situated. I understand that an EV installer may have concerns about certifying or carrying out the work if they cannot visually inspect the cabling but I was wondering if I got an electrician to lay the cable for me and certify it's been done safely? I could just opt for a full installation but it feels a bit pointless running down a warranty when it's not being used.

Any advice would be greatly appreciated.

 

[Munroast]

I had presumed they just plugged into a 3 pin socket?

Do they have to be directly wired into the consumer unit (like a cooker) Our consumer unit is in the middle of the house - would be a big job getting a cable to the garage.

 

[Sard]

I had presumed they just plugged into a 3 pin socket?

Do they have to be directly wired into the consumer unit (like a cooker) Our consumer unit is in the middle of the house - would be a big job getting a cable to the garage.

I'm pretty certain they go directly to the CU.

 

[davelx]

A domestic 7.5kW Type 2 EV charger needs a dedicated 40A supply from the CU and the unit requires a type B RCD or a type A RCD with additional 6mA DC protection, though most home EV chargers are supplied with these. You may need a small additional CU to accommodate this.

You should ideally use 10mm² cable.

You may also need a dedicated earth rod for the charger, depending on your supply earthing method.

 

[AndyPRK]

They either go into the cu or even off the meter tails.

SWA cable is usually used so that it doesn’t require rcd protection until the charger. Well that’s the case on certain brands. Eg zappy

You can get a grant when you buy a car to install one.

Typical install for this brand.

Other brands tend to require earth rods or upfront rcds or pen fault detectors

 

[flameport]

I had presumed they just plugged into a 3 pin socket?

There are leads which can charge EVs that way, but they are intended for emergency/temporary use only and certainly not for everyday charging.

It would take a ridiculously long time to fully charge a vehicle that way, typically 20 hours upwards. Standard 13A socket outlets are not designed for such long term loading and will overheat and melt.

 

[Sard]

They either go into the cu or even off the meter tails.

SWA cable is usually used so that it doesn’t require rcd protection until the charger. Well that’s the case on certain brands. Eg zappy

You can get a grant when you buy a car to install one.

Typical install for this brand.

Other brands tend to require earth rods or upfront rcds or pen fault detectors

Thanks Andy. Could I please get some validation on this...

If I paid an electrician to wire an outdoor socket where my future EV would be but using SWA cable running through the house, could I then have the outdoor socket removed and an EV fitted when I'm ready? I don't have a need today for a socket there but it would allow me to have the work done in a way that has some degree of certification along the way and also less destruction in the future than just leaving a disconnected wire in a wall cavity.

 

[flameport]

Therefore I'm thinking if I could pre-emptively lay a cable from my CU, through my floorboards

That could be done.

Alternatively, have an electrician install the cable while the floorboards are up. They can connect one end to the CU, the outside end can just go into a small empty box on the wall, so the whole lot can be tested. When the charge point is required it's just a matter of removing the box outside and connecting the charge point to the cable.

 

[Sard]

That could be done.

Alternatively, have an electrician install the cable while the floorboards are up. They can connect one end to the CU, the outside end can just go into a small empty box on the wall, so the whole lot can be tested. When the charge point is required it's just a matter of removing the box outside and connecting the charge point to the cable.

That sounds perfect. Given my desire to minimise future work, I'm happy to invest in SWA cable for a belt & braces approach and I understand it offers some flexibility with regards to a CU based RCD? Also would there be any harm in having an outdoor socket, if I am to have something on the wall? I'm sure it would encourage me to hoover the car more often

 

[ericmark]

Because you don't want house supply through the same RCD as the EV supply the normal is to tap in before the CU so the cable needs to be able to take what ever rating the DNO fuse is, so even if 40 amp cable needs in the main to be able to carry 100 amp and often the RCD is at the charge point so SWA cable even if inside the house.

But the main thing is there are government grants, which you can only get when you buy the car, and if you use a registered installer, so very little you can do before hand, unless you find an installer and strike a deal with him to do in two parts.

So find an installer and ask, get it from the horses mouth not second hand, and see what the installer says.

 

[flameport]

Also would there be any harm in having an outdoor socket

No, although the circuit for the EV point needs to be for that only, so the socket would have to be removed when the EV point was installed.
6mm² or 10mm² 3 core armoured cable would be the usual choice.

 

[Sard]

No, although the circuit for the EV point needs to be for that only, so the socket would have to be removed when the EV point was installed.
6mm² or 10mm² 3 core armoured cable would be the usual choice.

Yep, that would be my intention. I wouldn't have the socket permanently. It's just alternative to having any other termination point there.

 

[Sard]

Because you don't want house supply through the same RCD as the EV supply the normal is to tap in before the CU so the cable needs to be able to take what ever rating the DNO fuse is, so even if 40 amp cable needs in the main to be able to carry 100 amp and often the RCD is at the charge point so SWA cable even if inside the house.

But the main thing is there are government grants, which you can only get when you buy the car, and if you use a registered installer, so very little you can do before hand, unless you find an installer and strike a deal with him to do in two parts.

So find an installer and ask, get it from the horses mouth not second hand, and see what the installer says.

Would the RCD issue be mitigated with a new CU in the future with individual RCD/MCB's? When I do my kitchen I'm going to have a new CU fitted

 

[ericmark]

There seems to be a problem with RCD's and I will be frank I really don't know the answer, there are 4 types, AC, A, F, and B and most houses have type AC or A but it seems car charging points need type F or B.

I am not convinced there is a real problem, however that does not really matter, it is if the installer considers there is a problem that matters.

So with my all RCBO consumer unit I can only get type AC or type A, (RCBO is RCD and MCB combined) so if an installer says must be type F then only way is taking supply before the consumer unit. So let the installer tell you what he wants.

We have debated the types of RCD on these pages a lot, but as far as you need to know, there is a problem and different electricians have different views, so pointless trying to tell you what to do. Let the guy who is going to install tell you what he wants, because he signs the paperwork so all that matters is what he says.

 

[flameport]

Would the RCD issue be mitigated with a new CU in the future with individual RCD/MCB's? When I do my kitchen I'm going to have a new CU fitted

The ideal option for the EV point is to use armoured cable, and only have an MCB at the consumer unit. Suitable RCD and DC protection is then built into the charge point itself, which avoids the problems of certain consumer unit manufacturers not offering certain types of RCDs.

Charge points with all that built in are more expensive - but they are an all-in-one solution. Cheaper charge points won't have some/all of the required protection in them, and that will mean buying separate device(s) and paying for them to all be installed, so the total end cost isn't likely to be much different.

When you get a new consumer unit, get one with a main switch and space for RCBOs or MCBs. Do not get a dual RCD or split load effort.

Because you don't want house supply through the same RCD as the EV supply the normal is to tap in before the CU so the cable needs to be able to take what ever rating the DNO fuse is, so even if 40 amp cable needs in the main to be able to carry 100 amp and often the RCD is at the charge point so SWA cable even if inside the house.

Not having the same RCD for the house and RCD is correct.
The rest is total nonsense.