EV Charger Installation - Cabling Query?

[DT1991]

Why not the supplementary earth rod path?

When put into maths it requires a stupid low Ra value which cannot in reality be sustained.

That's my understanding?

 

[Midwest]

When put into maths it requires a stupid low Ra value which cannot in reality be sustained.

That's my understanding?

But isn't that the case for all earth rods with ev chargers (don't they do an efli test), whether TT or supplementary earth rod?

 

[DT1991]

I dont think the maths is the same.

When PME and using a supplementary earth rod it takes into account the max current of the installation and this is put into the equation which brings up a low Ra value.[/QUOTE]

 

[Deleted account]

When put into maths it requires a stupid low Ra value which cannot in reality be sustained.

That's my understanding?

Yes we did some calcs at college when we did the course. It was nigh on impossible. I think 3 earth rods 1 meter apart 2.4 meters deep might do it. Depending on resistivity of the earth.
So they have given us a solution to the problem that is pretty pointless.

 

[Deleted account]

I dont think the maths is the same.

When PME and using a supplementary earth rod it takes into account the max current of the installation and this is put into the equation which brings up a low Ra value.

[/QUOTE]
You don’t take the pme into account when doing the maths as the rods are there in case you loose the neutral, thus loose the pme.

 

[Deleted account]

duplicate post again ok

 

[DT1991]

Sorry pete what do you mean by that?

 

[Deleted account]

The major point of TT for ev is in case of dropped neutral on supplier side.

That in itself is pretty rubbish that we have to prepare for faults that are nothing to do with our regs and are in the control of the DNO’s.

So we need to know that the earth rods being put in at the origin are adequate without the pme if the neutral is lost by DNO

 

[davesparks]

These are not my suggestions, they are what I was taught on the City & Guilds course in EV charging that I did. I dare say that anyone else who has completed the course would have been taught the same.

If these 'suggestions' amuse you, why not e-mail Bill Allan of NAPIT and laugh loudly at him while you tell him that you know more about EV charging than he does. Meanwhile, kindly desist from trying to me appear foolish. Fair enough?

https://professional-electrician.com/18th-edition/changes-introduce-shock-risk

I don't claim to know more about EV charging than anyone. However is is obvious (hopefully) that introducing an extraneous earth potential into an installation then connecting it to a big piece of exposed metal (car) goes against the basic principles of protection against electric shock.

I am not trying to make you appear foolish, I have no need to do this. By suggesting that one can laugh loudly in an email you have achieved this appearance without my input.

 

[davesparks]

if the prohibition of PME for EV chargers is to eliminate risk if the supply N is lost (as with metalclad caravans) the I can't see any reason to differentiate between inside or outside. a fault occuring would have a similar result, in or out. then, i have not done any research on EV so my knowledge is limited.

If the vehicle is inside then it is, technically, within the equipotential zone and becomes no different to any other exposed, earthed, metal in the building. The car being charged in the garage presents the same hazard as the class 1 freezer in the garage.