EV charger on garage CU

[matthew77]

Hi all,
First post so appologies if this is not the place to ask.

I'm after some help after receiving conflicting advise from a couple of electricians regarding the install of an EV charger on the outside of my garage, the garage is detached from the house.
Garage is fed with 10mm2 SWA from the main CU in the house with a 40A mcb, non RCD.
Within the garage is a small CU with its own type A RCD and 3 breakers.
6A for the LED lighting, 20A for a couple of sockets and an unused 32A .
The 10mm SWA was put in place at my request a couple of years ago when I had the garage built and driveway laid. CU in the house was replaced at the same time and has a spare capacity if required.
One electrician has said the unused 32A breaker is ok to feed a charger and the SWA to the garage is suitable.
Another chap says its best to run a separate SWA from house direct to the charger.
I am reluctant to have another cable put in under the new driveway if what's already in place is suitable.
The earthing system is TN-C-S and I'm told a separate earth rod maybe required depending on the type of charger I go for.
All I need to know basically, is if the current install allowed ? or must I have a separate feed to the EV charger from the house.


Many thanks

 

[Mikegh]

I would say it should be ok

Hard to know for sure without seeing everything

 

[brianmoooore]

The length of the 10mm2 SWA is the deciding factor, but I'd be very surprised if feeding the EV from the garage isn't absolutely fine.
Did the one who wants to run a new cable give any indication why?

 

[Zerax]

Subject to VD and a site survey, it sounds to me like you can use the 10mm SWA as suggested. There's plenty of options on EV charger these days that will mean you won't necessarily need an earth rod.

 

[Bidges]

No rod required for Zappi or PodPoint as they have have neutral/earth fault detection. Site survey should include checking for metalwork near the charge point which could be extraneous.
The Type A RCD will suffice for the EV charger, just feed from a suitably sized MCB.There is some installation info here - https://s3-eu-west-1.amazonaws.com/...-130012-13_-_Instalation_Guide_Solo_Arch2.pdf

 

[brianmoooore]

Fig. 5 on page 2 of that installation guide is a bit presumptive! My own EV charge point is fed from a 36 module DIN enclosure with many more blanks than devices, and I wouldn't have been at all happy if an installer had fitted an additional enclosure.

 

[matthew77]

Thanks for the replies.
Length of SWA is 12meters.
The chap that suggested a separate SWA to the charge point mentioned RCD selectivity but I'm not bothered if it takes out the garage rcd upstream from the charger. And also he said ideally the garage CU wouldn't be fed via the house CU, so Im guessing he means it ideally should be fed from the meter cupboard using henley blocks.
I guess they just have different opinions rather than one being wrong and the other right.
As long as the install I have now doesn't sound like its against any regulations then I'm happy.
Should the garage door be bonded ? Its an electric roller shutter.

 

[brianmoooore]

You said that the garage feed was just through a MCB, and not a RCD, so there is absolutely no reason for a separate box next to the existing CU. Ideally, the garage feed would be via a cartridge fuse rather than a MCB, but that's a minor point.

 

[matthew77]

Didn't know you could get din mounted cartridge fuses. What would be the reason you mention
it, just out of interest.

 

[brianmoooore]

Don't know of any cartridge fuses for consumer units these days, but MEM produced them for their boards a few years ago. Often fitted them for the likes of storage heaters and immersion heaters - things that needed short circuit protection but not overload protection.
The advantage of a fuse feeding the garage is discrimination. A short circuit in your garage, rather than overload, will trip the local MCB, and quite likely the one in the CU as well, but a fuse is much more likely to survive
If you did fit a separate box to feed the garage, it should be a switchfuse, not an enclosure with a main switch and a MCB.
Don't need to do calculations for 12m of cable. It will be well within limits. As a general rule, it's when you get to about 50m that you need to do the calculations.