EV chargers and TN-C-S supply earthing general hassle

[Other_Tucker]

Trying to understand why car chargers attract this earthing ballache. from what I learnt it's all about the rare times a Neutral / PEN conductor gets broken in a TN-C-S or thesedays most TN-S supplies.

1) If the PEN gets disconnected in the street, N and CPC become live making the car >70v. Won't everything in the house be just as dangerous? Radiators, dishwashers etc, Why are they so ----y about EV chargers especially?

2) Why is TN-C-S becoming most common if it's dangerous? There were 500 incidents a year reported

3) Electric cars are almost all plastic on the outside, can the mfrs just make them as class II appliances with no external earthing? Like arden equipment

 

[Midwest]

Here's an interesting video from John Ward if you've not already seen it.

 

[Other_Tucker]

Here's an interesting video from John Ward if you've not already seen it.

That's where I started, great explanation of how and why, but I'm still missing the part where EV chargers need specialist courses and earth rods but a lawnmower socket circuit just needs an rcd and earth.

If the PEN fault is just as rare and dangerous for everything else, the seem to be picking on EV's. Maybe it's DC related?

 

[DPG]

Trying to understand why car chargers attract this earthing ballache. from what I learnt it's all about the rare times a Neutral / PEN conductor gets broken in a TN-C-S or thesedays most TN-S supplies.

1) If the PEN gets disconnected in the street, N and CPC become live making the car >70v. Won't everything in the house be just as dangerous? Radiators, dishwashers etc, Why are they so ----y about EV chargers especially?

2) Why is TN-C-S becoming most common if it's dangerous? There were 500 incidents a year reported

3) Electric cars are almost all plastic on the outside, can the mfrs just make them as class II appliances with no external earthing? Like arden equipment

When you touch the car you are stood on the ground which makes it more hazardous.

There are many electric cars which have metal bodies.

 

[marcuswareham]

1) If the PEN gets disconnected in the street, N and CPC become live making the car >70v. Won't everything in the house be just as dangerous? Radiators, dishwashers etc, Why are they so ----y about EV chargers especially?

Yes, but inside a house you are in an equipotential environment and anything metalic bringing in true earth from outside is bonded so will rise in potential along with the radiator and dishwasher etc, There is a risk for things like outside lights (although not often touched) but definitely outside taps which also add water to the situation in my opinion are as much if not more of a risk than EVs

2) Why is TN-C-S becoming most common if it's dangerous? There were 500 incidents a year reported

Because its cheaper, when you need to run that much cable one less conductor probably gives a sizeable cost saving, Some would also argue for the very low Ze (high fault current) but this could also be achieved with true TN-S if all conductors are equally sized

3) Electric cars are almost all plastic on the outside, can the mfrs just make them as class II appliances with no external earthing? Like arden equipment

Really? A few friends of mine have electric cars and they seem to have metal body panels.
I wonder if the metal body of the car could be connected to the DC battery ground (like a standard car) and the charging circuit inside the car is housed in a double insulated enclosure and had suitable isolation transformers from the AC to DC side therefore removing any risk if the CPC has a high voltage on it, perhaps there is a reason not!?
But this would make the car class 2 as you say but allow manufacturers to use any construction materials

 

[Midwest]

That's where I started, great explanation of how and why, but I'm still missing the part where EV chargers need specialist courses and earth rods but a lawnmower socket circuit just needs an rcd and earth.

If the PEN fault is just as rare and dangerous for everything else, the seem to be picking on EV's. Maybe it's DC related?

If you are aware of the potential dangers, after additional training if necessary, then thats fine to go ahead and install it for people. Some people just seem to plough ahead regardless.

It might be just rare and dangerous, but it will only take just one instance, which might prove fatal. After all, its a large metal box connected to electricity, but isolated on 4 rubber tyres, just waiting for someone to come along and touch it.

Most electric lawnmowers I know of, are Class 2.

 

[LastManOnline]

Trying to understand why car chargers attract this earthing ballache. from what I learnt it's all about the rare times a Neutral / PEN conductor gets broken in a TN-C-S or thesedays most TN-S supplies.

You raise a reasonable point.Electric gates ,heat pumps etc ( plus all outside metalwork) all carry the same risk under open PEN circumstances.Perhaps it is the fact that people clean their cars far more often than they clean their gates or heat pumps is what finally caused the regulators to decide that " we need to take steps to mitigate danger " should a broken neutral occur in a TNCS system.