Electric Vehicle Charging & PME

[Stugadget]

I will shortly be installing POD Point Electric Vehicle Charging units and I am very confused by the earthing requirements if the property has a TN-C-S Supply.


I have read the installation manual of the POD Point, Amendment 2:2013 of BS 7671:2008 and the IET Code of Practice for Electric Vehicle Charging Equipment Installations.


My initial thoughts were that if the car was to be charged outside of the house then I could not connect to the PME earth terminal and I would have to make the circuit a TT by the installation of an earth rod.


I found this article on the NET Electric Vehicle Charging | Professional Electrician & Installer and the last paragraph states "Based on the HSL report, the decision was taken to permit the use of PME supplies to charge electric vehicles – subject to the requirements of Regulation 722.411.4. "


Regulation 722.411.4 is in Amendment 2:2013 of BS 7671:2008 which is reprinted in the second part of the article Electric Vehicle Charging: Part Two | Professional Electrician & Installer the author has added this paragraph.


"An exemption is made for dwellings. None of the following requirements need be applied for the charging point at a dwelling if it is not reasonably practicable to do so. This means that the requirements of this regulation may or may not be applied to a dwelling. "


What gives the author the authority to add that paragraph as its definitely not in Amendment 2 :2013 ?


So what is your opinion can I connect the earth of the Charging Point to the main earth connection in a house with a PME supply ?

 

[baazab]

good question ,sorry cant help but im sure one or two will help you

 

[uksparks]

I'm booked on to do the C&G 2919 course on vehicle charging points so that I have a better understanding of it in the event that I ge the opportunity to fit one.

Dont hold me to this as I don't know, but I'm under the impression you have to put an earth rod in and have isolation from the PME supply. I not know, this is why I'm going on a 2 day course.

 

[wozz]

I'd go with what the regs say, the article points you to 722.411.4. I don't have regs with me at the moment but that's where I would be looking.

Is the point internal or external you are installing?

 

[Stugadget]

I'd go with what the regs say, the article points you to 722.411.4. I don't have regs with me at the moment but that's where I would be looking.

Is the point internal or external you are installing?

Hi Woz

its external

 

[Engineer54]

It just amazes me that a fully qualified electrician needs take a bloody course and hold a separate Qualification (C&G 2919) for what is, installing a Frigging Socket Outlet!!

Just read those linked articles, ....a bunch of knob's fluffing around that can't make up their mind one way or the other it seems to me... If they are incapable of coming up with a requirement, pinch those of the Germans/French, they both have the same requirement, though i doubt if the electricians need a separate qualification to install the bloody things!!

All this crap, over providing a charging socket!!

 

[Richard Burns]

"An exemption is made for dwellings. None of the following requirements need be applied for the charging point at a dwelling if it is not reasonably practicable to do so. This means that the requirements of this regulation may or may not be applied to a dwelling. "


What gives the author the authority to add that paragraph as its definitely not in Amendment 2 :2013 ?

Since that statement is clearly made in the referenced regulation the author can certainly state it.
This provides an exemption for dwellings if it is not reasonably practical to do i) ii) or iii) and since the earth electrode resistance would need to be from 1 to 2.5 ohms I cannot see this being achieved in any domestic property without considerable difficulty and expense.

 

[uksparks]

Since that statement is clearly made in the referenced regulation the author can certainly state it.
This provides an exemption for dwellings if it is not reasonably practical to do i) ii) or iii) and since the earth electrode resistance would need to be from 1 to 2.5 ohms I cannot see this being achieved in any domestic property without considerable difficulty and expense.
View attachment 23235

Where did you get this 1 to 2.5 ohms figure from?

I keep looking at pics or wall chargers, and none of them appear to have eath rods.

 

[Richard Burns]

Where did you get this 1 to 2.5 ohms figure from?

I keep looking at pics or wall chargers, and none of them appear to have eath rods.

The 1 to 2.5 ohms was from annex 722 using the formula

As required by 722.411.4.1 (ii)
If the maximum demand of an installation is from 40A to 100A then using that formula the Raev must be less than 2.515Ω to less than 1.00Ω respectively.

 

[davesparks]

What the hell is the point of a regulation which states that you can ignore this regulation if it is not practical to comply with it?

I know the big green book is a big grey area but surely this just takes the biscuit?

 

[Richard Burns]

Because the original COP stated that you must TT (unless the TNS can be guaranteed never to be changed to TNCS!) and no conductive parts from the existing installation can be within 10m, which would cover most of a domestic residence and so is totally unworkable and dumb; this is their method of backing down slightly!

 

[uksparks]

Well it does appear that nobody puts a rod in and just leaves it connected.

So if I am correct then, unless you can get a new rods Ra to less than 2.5 ohms you can stop trying and just extend the PME earth.

 

[Richard Burns]

For a single phase supply in a dwelling and before the product standard for an earth leakage circuit breaker is prepared then, yes.
(and the 2.5Ω would be for a 40A maximum demand)

 

[Engineer54]

I'd warrant that very few of these non domestic Electric Vehicle Charging Points have a TT system Ra value that is 2.5 ohms or less. In fact i'd put money on it, based from the posts we get on here and on other forums regarding installation of rods/electrodes etc!!... lol!!

 

[hfdsparky]

As I understand it the very low values of RA (2.5 ohms etc) that are being stated are for when you are providing an additional earth electrode connected to the PME main earth terminal and not for TT'ing an EVC, the reason being to ensure that in the event of a loss of neutral voltages to true earth don't exceed 70 V.