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Recently I have had to have the consumer units at most of my rentals upgraded to metal boxes. This was legislated due to the number of plastic ones that caught fire. Though this was painful financially, I now think it was a good idea.

I see that the breaker in a lot of Rolec chargers seems to be melting and smouldering. This is bad enough on the outside wall of your house, but I know a number of people have them in the garage. I actually have a quite old aluminium ev charger in my collection, so it is possible to make them.

What do you guys think? Wouldn't you prefer a metal clad charger?
 

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I like the long term robustness and fire protection of metal, but I can see it raising some issues on outdoor chargers because of the earthing arrangements.

I think for outdoor use an insulated enclosure made of plastic or other insulating material is better.
 

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I like the long term robustness and fire protection of metal, but I can see it raising some issues on outdoor chargers because of the earthing arrangements.

I think for outdoor use an insulated enclosure made of plastic or other insulating material is better.
Better quality EV chargers such as Viridian's are made of metal. Not a problem with the earthing.
 

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Better quality EV chargers such as Viridian's are made of metal. Not a problem with the earthing.
Some of the new charger models incorporate protection against loss of neutral on PME supplies, where this can cause the earth to rise to a dangerous voltage, they automatically disconnect the earth.

Be interesting to see whether this is possible with a metal enclosure.
 

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Recently I have had to have the consumer units at most of my rentals upgraded to metal boxes. This was legislated due to the number of plastic ones that caught fire. Though this was painful financially, I now think it was a good idea.
18th edition regulations weren't retrospective, but landlords need a recent EICR, and the coding for that depends on a number of factors, so unless there's other issues, the old plastic units that otherwise conformed to the regulations are often still good for EICR coding. Likewise, should regulations about ev chargepoints change, it would depend on the setting. Thinking of it, many current public EV chargepoints, and most designs for private use have a plastic shell, but most of them aren't installed underneath a wooden staircase that is the only fire exit from upper levels. Horses for courses.
 

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Some of the new charger models incorporate protection against loss of neutral on PME supplies, where this can cause the earth to rise to a dangerous voltage, they automatically disconnect the earth.

Be interesting to see whether this is possible with a metal enclosure.
A metal enclosure can be unearthed with all internal components having reinforced insulation, not hard.
 

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As understand the Viridian wiring diagram, the Earth that gets disconnected is only the length of Earth wire that runs from EVSE socket to the car, via the (un)tethered cable. The Earth line back to the house is not disconnected. If the metal EVSE case is Earthed, it should stay that way (assuming it's not gone open circuit at some stage). Dunno if this helps the discussion?
 

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Some of the new charger models incorporate protection against loss of neutral on PME supplies, where this can cause the earth to rise to a dangerous voltage, they automatically disconnect the earth.

Be interesting to see whether this is possible with a metal enclosure.
What is the difference between the metal enclosure of a charge point on an outside wall and the metal enclosure of the car a couple of feet away and plugged into that point?
It's all just exposed metalwork and dealt with in the same way.
 

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As understand the Viridian wiring diagram, the Earth that gets disconnected is only the length of Earth wire that runs from EVSE socket to the car, via the (un)tethered cable. The Earth line back to the house is not disconnected. If the metal EVSE case is Earthed, it should stay that way (assuming it's not gone open circuit at some stage). Dunno if this helps the discussion?
The EVSE enclosure will be connected to the 'car' earth line, not the house earth.

All earths are not equal - which is exactly why this PME/TT thing has become an issue.
 

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What is the difference between the metal enclosure of a charge point on an outside wall and the metal enclosure of the car a couple of feet away and plugged into that point?
It's all just exposed metalwork and dealt with in the same way.
No, metal car bodies are earthed, that is the STD there is no choice. A metal bodied EVSE can be entirely unearthed ( see my previous post)
 

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It would really help to have a set of simple diagrams showing the actual wiring route, along with an obvious fault in the relevant wire somewhere, along with the resulting path of the current that would begin to electrocute the operator, for each of the different faults that could occur (Loss of N wire, loss of Earth somewhere, steady leakage of DC current from car back down some wire into EVSE that "blinds" the AC-sensitive RCDs & stops them doing an AC mismatc detect, etc).

The diagrams should show the device that successfully detects this fault, and where to put it.

E.g. I have an RCD in my mini-CU, and an RCBO inside my EVSE housing. Do I need both? Not a clue. I've seen the insides of one EVSE that had no RCBO/RCD inside, doubtless relying on domestic RCD to protect it. Is this adequate? We're seeing a lot of repeat questions about Earthing, the various flavours of (Island, whatever, all Greek to me) from people such as myself who have a smattering of electrical knowledge, but not the depth & experience of professional sparkies. And my smattering has allowed me to improve my own EVSE's safety, but I'm still in the dark about some details that I'd like to get my head around.

There's one diagram that's been posted a couple of times in here (& repeated below for ref). I've looked at it & I find it somehow insufficient. It's not clear to me exactly where the mini-CU for the EVSE's sole use is located (let's assume we have one right beside the big house CU), and where the EVSE enclosure is. In this diagram, yes, the RCD doesn't detect any current imbalance (there isn't any to detect), is this because it's located inside the EVSE?

In my setup I have an RCD in my mini-CU as well as the EVSE one. Surely a broken N wire as shown here might not be picked up by RCD in the EVSE, but would be detected by the RCD in mini-CU, no? (Again, we need a lot more similar diagrams I think, 1 per scenario. Then the experts could simply refer qns to the relevant diagram. Maybe add diagrams for houses with looped supplies, explain what's meant by TN-C-S in words of 1 syllable etc).

Page from "NICEIC-EV-Brochure.pdf" kindly posted earlier.
138893
 

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What is the difference between the metal enclosure of a charge point on an outside wall and the metal enclosure of the car a couple of feet away and plugged into that point?
It's all just exposed metalwork and dealt with in the same way.
Well it's not quite the same, once the charge-point contactor and earth isolator (on the latest designs with open PME neutral fault protection built-in) open the car is completely isolated from both the supply and the earth. But there is still a live supply going into the charge-point, with a risk of a fault to the metal casing, requiring the enclosure remains earthed, or a different insulating arrangement such that this cannot occur.
 

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Well it's not quite the same, once the charge-point contactor and earth isolator (on the latest designs with open PME neutral fault protection built-in) open the car is completely isolated from both the supply and the earth. But there is still a live supply going into the charge-point, with a risk of a fault to the metal casing, requiring the enclosure remains earthed, or a different insulating arrangement such that this cannot occur.
The EVSE metal casing can be left disconnected from any earth, provided the manufacturer has designed it as such and the installation instructions specify the same. There are commercially available public chargers installed in the UK that already follow exactly this practise. It's all about reinforced and to a lesser extent double insulated construction.
 

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No, metal car bodies are earthed, that is the STD there is no choice. A metal bodied EVSE can be entirely unearthed ( see my previous post)
Yes, but if it is earthed it should be to the outside (rod, whatever) not the PME.
 

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E.g. I have an RCD in my mini-CU, and an RCBO inside my EVSE housing. Do I need both? Not a clue. I've seen the insides of one EVSE that had no RCBO/RCD inside, doubtless relying on domestic RCD to protect it. Is this adequate? We're seeing a lot of repeat questions about Earthing, the various flavours of (Island, whatever, all Greek to me) from people such as myself who have a smattering of electrical knowledge, but not the depth & experience of professional sparkies. And my smattering has allowed me to improve my own EVSE's safety, but I'm still in the dark about some details that I'd like to get my head around.
If you don't really understand this stuff are you sure you've improved your EVSE's safety?

I do worry about the way people who clearly have little electrical knowledge are encouraged to "just change the cable/fit a new contactor/whatever". They'll probably do it OK 90% of the time ... but then there are the other times.
 

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If you don't really understand this stuff are you sure you've improved your EVSE's safety? ...
Yes. Prev controller had no PEN-loss detection, and on earth-leakage detection either. Was totally reliant on RCD in mini-CU, and RCBO in EVSE.
Newer EPC 2.0 controller has replaced previous (from same reputable mfr), wired as per supplier diagram, so now has PEN-loss protection plus added Contactor to disconnect Earth going to car, and I've included the optional DC leakage detector that trips if there's 6mA of DC current being leaked. Original installation was 5 years ago, predated 2018 new regs.

That said, I'd still like to understand the different earthing systems, why they exist, and why some sparkies are less than keen on these PEN-loss things, which appear to mean you don't need an Earth rod if you fit them. If an Earth rod is better, what's not so good about PEN-loss detectors? And why are PEN-loss detectors approved, if they're not "wonderful" ? I'm sure I'm safer, but have I gone totally OTT?
 

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That said, I'd still like to understand the different earthing systems,
It‘s all down to the principles of EEBADS - earthed eqipotential bonding and automatic disconnection of supply.

The risk of electric shock is all down to having different parts of your body in contact with different potentials, therefore allowing a current to flow through you. Equipotential bonding limits the risk of that by bonding all exposed metal parts together so you can’t touch two different things at different potentials and get a shock.

The purpose of earthing the bonded parts is that places them at the same potential as the general mass of earth, so in the case of a fault that makes your water pipes live, there is no potential difference between them and the floor or anything else in contact with earth.

if you now connect the earthed and bonded items to the return of the supply circuit, a fault that contacts an exposed metal part will draw either a large current or create a residual imbalance, operating either an overload (eg MCB) or residual (eg RCD) device and disconnect the supply.

This is all easy to achieve inside because it’s hard to be in contact with “earth” and everything else is bonded so you are well protected within the equipotential zone. The problem comes outside because if you have a PME system, your indoor “earth” is just a copy of the supply return conductor and is only connected to real earth at the substation, some distance away.

Normally this isn’t a problem but in the event that the substation transformer becomes disconnected from earth, you are still protected indoors; however, outside the equipotential zone, there could now be a potential difference between your earth and real earth. Connect the car to house earth and stand on real earth and you are at risk of a shock from that potential.

If you provide an earth rod, the car‘s earth is at the same potential as real earth so no potential and no shock. BUT you can’t connect the earth rod to the house earth, otherwise you have just created an earth return path for fault current for everyone in your neighbourhood.

The PEN fault detector works by detecting the loss of substation earth and disconnecting the supply, including the earthed neutral to the car. It’s not the presence of charging supply to the car that creates the risk, it’s the PME connected neutral because the body of the car is connected to that, whereas the earth around it is at earth potential. In the event of a disconnection between the star point of the transformer and earth, the neutral will float away from earth potential when there is an imbalance between the phases, creating a potential difference between the car’s bodywork and the ground it stands on. .

Hope that helps!
 
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