EV charger earthing

I've only just spotted that EV chargers on TN-C-S systems are now supposed to be earthed as TT systems, with their own earth rod. AFAIK this wasn't the case in 2017 when I installed my (Rolec) charger, so the CPC to the charger is connected to the earth bar in the CU which, coincidentally, is also connected to an earth rod that's positioned almost directly below the charger. I don't see that there is a real-world risk from my current charger earthing arrangement but I'm thinking through the options: leave it as it is, or install a second earth rod (which would need to be very close to the existing one). Any comments from the assembled jury?
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On 15/03/2019 23:07, snipped-for-privacy@aolbin.com wrote:

That only applies if you are charging a car outside.
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Adam

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On 16/03/2019 07:01, ARW wrote:

Yes, that's what I'm doing. The car is charged outside the garage; the charger is on an outside wall.
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On 16/03/2019 08:52, snipped-for-privacy@aolbin.com wrote:

I'll have to get out my EV installation manual.
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On 15/03/2019 23:07, snipped-for-privacy@aolbin.com wrote:

They added a specific section (722) to the 18th edition:
This basically applies where the charging will take place outside, rather than say in a garage.
Its pretty much the same rules as for any PME supply used outside of the main equipotential zone, plus it also requires the use of (at least) a type A RCD [1]
[1] http://wiki.diyfaq.org.uk/index.php/RCD#Electrical_and_Trip_Characteristics

Its unlikely to kill you, but there is the traditional danger associated with PME systems, that could result in the CPC/PEN conductor voltage rising to mains potential under some fault conditions (e.g. a disconnection in the PEN conductor of the supply). This is potentially dangerous if you are outside of the equipotential zone and have ready access to a local earth.
So normally I would do it as a TT install with the submain protected by the TN earth as far as the point of use, then it would be isolated at that point, and the local earth used for the installation. Ideally however the earth spike should be driven far enough away from the existing one to not overlap resistance area.
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On 16/03/2019 13:56, John Rumm wrote:

In my case the house is fed from an overhead line to the final pole and then a short (new) underground run to the (attached) garage. It's marked TN-C-S but there is also a connection to an earth rod that's just outside the garage, so I don't see that a supply fault could cause a safety issue. Have I missed something? The furthest extremity of the car plus cable is about 8m from the charger and existing earth rod. Any new rod that I added would need to be within a metre of the existing rod and would still be the same distance from the car extremity - I don't see that a new rod would change the risk. I suppose I could reduce the small risk of a disconnected cable by connecting the charger earth directly to the existing rod rather than the CU earth bar (leaving the rod's connection to the supply) but that hardly seems bothering with. Again, have I missed something? As always, I'm very grateful to be able to bounce these ideas around. Thanks.
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On 16/03/2019 15:19, snipped-for-privacy@aolbin.com wrote:

PME setups can have a local earth rod - it just becomes one of of the "multiple" earths that the name suggests.

The classic case would be loss of the Protective Earth and Neutral close to your installation. That could leave a local combined earth and neutral floating, and connected to line via all the loads in your installation - hence the voltage would tend to rise toward line potential, taking all the earthed metalwork in the installation with it.
In reality, the chances of this happening are very small since the supply is earthed at multiple locations. Since you have an additional earth rod, that will limit the voltage rise on the earth - but how much will depend on the earth impedance via that rod. You may also get some additional fortuitous earthing from your equipotential bonds to other incoming services.

An additional rod can be at a distance from the point of use so long as the connecting wire to it is adequately protected / of a suitable size.
The distance to the car does not make much difference AFAICS.

You could disconnect the main CU from the earth rod altogether, and use that just for the TT earth for the charger. That way if there ever was a voltage rise issue, it would only affect the house and not the independently earthed charger. If you add an additional rod, then it needs to be far enough away from the existing that you don't end up in effect joining them with a short distance of soil.

As I said earlier - in reality the risks are tiny, and you have RCD protection for the charger anyway.
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On 16/03/2019 22:00, John Rumm wrote:

I was thinking of the potential gradient to the earth rod.

Yes. Unless someone comes up with something else to consider I think I'll leave it as it is.
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On Saturday, 16 March 2019 22:00:28 UTC, John Rumm wrote:

I'd say the risk of dangerous CPC voltage rise on a TT setup is worse than PME, so you're better off keeping the rod as another PME element than using it just for the charger feed.
NT
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On 18/03/2019 08:19, snipped-for-privacy@gmail.com wrote:

I don't see that there is a real-world risk from my current charger

Assuming you want to follow the regs requirement for the "outside" EV charger to be TT, then you would need a separate TT earth for dedicated use by the EV charger. Separate as in not the same, and also as in not overlapping the resistance area of the main rod. If that is difficult to achieve that separation, then re-purposing the existing spike will solve that issue.
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On Monday, 18 March 2019 10:40:08 UTC, John Rumm wrote:

OTOH there's no regs requirement to upgrade your own residence in this respect, and in this case no safety upside in doing so.
NT
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On 18/03/2019 22:01, snipped-for-privacy@gmail.com wrote:

That would only be true if the work were carried out at a time when PME supplies could be brought out of the equipotential zone without extending it. Since I don't think there ever was a time this was the case, it would not have been compliant in the first place.
(I agree however its not a big issue)
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On Tuesday, 19 March 2019 01:06:50 UTC, John Rumm wrote:

When noncompliant there's no requirement to compliantify it in most cases.
NT
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On Friday, 15 March 2019 23:07:47 UTC, snipped-for-privacy@aolbin.com wrote:

They don't earth the frames of solar panels either. You get a definite prickle if you touch one.
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