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I've never installed a charging point and unfamiliar with accepted practice, but I can say with certainty that no 7kVA wirewound transformer ever mounted on a DIN rail. It will be in the order of 50-60kg and the size of a case of wine unenclosed. This is due to physical limitations of the copper and steel, and until someone invents a revolutionary material with better properties, it won't change much. It is possible to make a smaller, lighter switched mode converter, although not for a few hundred pounds.

But, surely the sensible approach is a device that disconnects the supply in the event of the PME earth exceeeding 70V to local mass of earth, as detailed in 722.411.4.1 option (iii). Put in two small spikes nearby (resistance need not be very low, and the two would allow for automatic monitoring of resistance), see the green light come on and the job is done. It's basically an improved version of a VOELCB used for a more suitable purpose, obviously with a bit of engineering to make it reliable enough to switch the PE as well as the live conductors.

I have to wonder why the charging point makers don't offer an integral solution. 722.411.4.1 option (iii) even suggests the voltage detection device could be included in the charging equipment. The convenience of being able to install one product to any supply without further complications would surely be attractive in spite of increased cost.
We asked the same questions as to why the manufacturers such as Rolec dont install them, I’ve heard another manufacturer does include the device but I cant find who does it
 
The guidance I received on acceptable TT Ra test results where the charge point was 32A and supplementary earth rod was to be installed on the MET of a TNS or TN-C-S was an RA less than 5Ω was considered stable where as it’s less than 200Ω for whole house TT rod. The other issue is this 10 meter zone. When charging leads can be 7.5Mtrs in length and the charging ports on the cars are not all in 1 standard location. So it is possible for the vehicle to be charged in different locations on the drive plus add the vehicle length, difference in plug location you could have an earthed metallic pipe or fitting that is not reachable with say a Nissan Leaf but you chuck a Tesla on the drive it suddenly becomes very touchable.
 
Good news leebut the voltage potential difference device that wasn’t invented when the ev charge code came out is now in production.

There was a recent threat on this issue and more information is on there.

I will try to locate the thread.
[automerge]1568446857[/automerge]
Have a look at the thread “Updates to 722”.

Not the thread I was looking for but it’s relevant
[automerge]1568447034[/automerge]
“EV Charger Installation - Cabling Query?” This was the thread I was originally looking for.
 
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So you install an isolating transformer, the trailing cable gets damaged and the "L" gets earthed. The car is now at 240V until someone touches it and the ONLY protection is the load-side RCD. Or put another way, the only protection against shock in that case is a device that's known to fail from time to time - I think we've all, or at least a lot of us, come across RCDs that don't trip when tested.
You also need active monitoring to ensure that (eg) insulation breakdown in the transformer or wiring doesn't make the vehicle "hard" to 240V (or some subset of it) with zero protection other than any upstream RCD.
Might as well save the cost (and bulk) of the transformer and just have active monitoring of CPC vs local ground voltage as already mentioned.
 
So you install an isolating transformer, the trailing cable gets damaged and the "L" gets earthed. The car is now at 240V until someone touches it and the ONLY protection is the load-side RCD.

The car is only at 240V relative to the other pole of the transformer output, it will not present a shock hazard unless the person is in contact with the other pole of the output at the time they touch the car.
 
There is a good source of devices to allow you to use chargers on a pme system. Cost around £130 per unit pdfs below.
Havent used one yet as i opt for the pod point solo or go down a tt set up.
 

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OP, could you clarify - were you meaning make the whole house electrical system TT?
Yes the wiring regulations states you cannot install a car charging unit onto a PME supplied installation if you are to install the car charger as a TT system on it’s own there cannot be any metal conductive parts or class 1 external light fitting within a 10 metre area of the charging point which on a new housing estate would be impossible to achieve
 
I’ve done a load more research on these EV charging points and I’ve now found out that a company called Zappi is producing a charging point that doesn’t require an earth rod the model you need to check out is the Zappi V2
 
I’ve done a load more research on these EV charging points and I’ve now found out that a company called Zappi is producing a charging point that doesn’t require an earth rod the model you need to check out is the Zappi V2
There’s another one, probably more now. See post 28.
 
Theres about half a dozen companies making EV chargers that dont require TT'ing.Zappi's are on an 18 week order time at the moment.

@leebut you said you cant install a charger on a PME system, but I'm sure you are aware that statement isn't correct if you did the course?
 
Theres about half a dozen companies making EV chargers that dont require TT'ing.Zappi's are on an 18 week order time at the moment.

@leebut you said you cant install a charger on a PME system, but I'm sure you are aware that statement isn't correct if you did the course?
I did the course, the regs say you can’t install on a PME supply due to the risk the earth might fail
 
But there isn't a high risk of the earth failing, there is a high risk if the supply neutral were to fail.
These two things are very different.
On PME if the neutral cable is to get damaged the earth also fails as it’s the same conductor!!

hence the IET’s concern!!
 
Yes, but that doesn't mean there is a high risk of it failing, it means there is a high risk if it fails.
The risk of it failing is low,
I’m not the one making the Regs or arguing over them I’m just trying to comply with them, if the Regs say we can’t install an EV charging point on a PME we don’t do it, otherwise what happens if someone gets killed through your neglect.

I don’t like the idea that they say you convert the home to a TT system from PME, what happens when another electrician comes along again who doesn’t know the Regs reconnects to the PME and someone dies how do YOU prove you did what you did correctly and someone else has changed it, because he’s not going to admit the changes if he’s facing a manslaughter charge!!
 

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