UK EV Charger Earth Rod

[Strima]

However it is clear you can't really have earth electrodes and PME earth bonded together, at least not a good earth electrode, 60 ohm would be OK, but would guess his earth was better than 1 ohm.

It's a DNO requirement that street cabinets on a PME system have a supplementary earth electrode installed. Depending upon the expected maximum demand the resistance can vary but over a certain measurement the cabinet earthing must be converted to TT.

 

[Midwest]

I have it in my mind, from something I watch, possibly E5Group vid, that the earth rod to MET option in Section 722, the Ra has to be ridiculous low for it to comply.

 

[Ian1981]

I have it in my mind, from something I watch, possibly E5Group vid, that the earth rod to MET option in Section 722, the Ra has to be ridiculous low for it to comply.

The annex to section 722 gives example calculations for the purpose of supplying an electrode to supplement the existing pme earthing Incase of an open PEN conductor and your right, the resistance is very low to achieve compliance

 

[EricMark]

An extraneous-conductive-part or earth rod? One must remember being told as an apprentice you can't have earth rods on a TN-C-S supply, it was the trick question, as any earth rod was called an extraneous-conductive-part.

But with any cable there needs to be a current rating and traditionally with PEN it was 10 mm² but with TT it could be far smaller, and what we need to consider is will the cable take the earth current.

So in a workshop all bonding conductors were 25 mm² to ensure they would not melt, in that case it was due to welding currents, but the same applies to any PEN supply, had that friend used 16 mm² then likely it would have not melted and all would have been fine.

But in real terms we use resistors when connecting two earth systems, I have only seen it done once at point of aye gas terminal a box around 4 foot square had a massive resistor and the DNO earth and site earth were connected across that resistor so even if the DNO earth went to 230 volt nothing would burn out.

Clearly a single rod or 60 Ω is not going to allow enough current to flow to cause a problem, and if you have a water pipe connected at every house then because any fault is shared again no real problem, only when the site has really good earthing system is there likely to be a problem.

However just like when measuring the loop impedance in the main lower the better but if the prospective short circuit current exceeds the rating for protective device 4.7 kA or 10 kA then we may need a fuse or moulded breaker to take the fault current, the same applies to an earth, there is such a thing as an earth being too good.

Thing is I have never seen a fuse in an earth, only answer is a resistor, and as with many things because I have never needed to work out the size of a resistor I have never looked at how one works it out.

 

[Risteard]

I'm sorry EricMark but I can't agree that an Earth electrode in any system type is an extraneous-conductive-part as it forms part of the electrical installation.

 

[EricMark]

I'm sorry EricMark but I can't agree that an Earth electrode in any system type is an extraneous-conductive-part as it forms part of the electrical installation.

I lump of metal in the ground can have many names, pipe, re-bar, earth rod, girder, it depends what it is used for what name it is given, so connecting a steel rod coated in copper to the electrical system could be a sacrificial anode, it all depends what it is used for, so it may be classed as either an extraneous-conductive-part or earth rod, the designer gives it a name, we all know in old houses often the connection to earth rods has gone and only real earth is the water and gas pipes, but that does not make them earth electrodes, because they were not designed to be earth electrodes, it is just a name.

 

[Strima]

Earth electrode to be pedantic.

 

[bigspark17]

You could achieve protection with two RCDs in series:

• First one is the normal 2-pole RCD/RCBO that you would use to protect the AC supply to any outside sort of unit. Would protect against typical L-E faults.
• Second one feeds L, N and E through a "4-pole" RCD so in the event of CNE open and someone touching the car, the shock current is detected on the E line and it then trips isolating all wires. (L & N should always balance, here they are needed simply so they are isolated simultaneously with the earth disconnection, but L-E fault will not trip in this case)

No earth rods and risk to buried services, no worries about being on the wrong phase and not seeing enough of an out-of-range voltage to trip the likes of the Matt:e boxes.

i dont agree with that? Your suppost to eliminate the car shell becoming live should a open PEN conductor occur not wait for someone to have a shock and hope the rcd trips which it wouldnt with the loss of neutral conductor!

 

[Midwest]

i dont agree with that? Your suppost to eliminate the car shell becoming live should a open PEN conductor occur not wait for someone to have a shock and hope the rcd trips which it wouldnt with the loss of neutral conductor!

I think that post, was a have.

 

[bigspark17]

Have a look at the MyEnergi Zappi car charger no need for earth rod no need for rcd and moniters the current so that it wont exceed the main fuse

View: https://www.youtube.com/watch?v=DnEG8jhOHBw

does look a good charger. Do you have to be trained by the manufacturer to fit them?

guy in video, has no single point of isolation for the installation Now. The earth & blue sleeving used was rather large, no spd? But dont know when it was filmed..

 

[Markyd]

does look a good charger. Do you have to be trained by the manufacturer to fit them?

guy in video, has no single point of isolation for the installation Now. The earth & blue sleeving used was rather large, no spd? But dont know when it was filmed..

No spd required.......it's only a recommendation to have one and I believe you have to do a course to get a qualification to fit car chargers

 

[Ian1981]

No spd required.......it's only a recommendation to have one and I believe you have to do a course to get a qualification to fit car chargers

You do not have to do a course to fit EV chargers.
Maybe not required for the EV charger, but SPD,S are not a recommendation, they are most certainly required in the 4 indents given in the regulations , apart from the cravat detailed in regulation 443.4 but that does not make them a simple recommendation.

 

[Markyd]

You do not have to do a course to fit EV chargers.
Maybe not required for the EV charger, but SPD,S are not a recommendation, they are most certainly required in the 4 indents given in the regulations , apart from the cravat detailed in regulation 443.4 but that does not make them a simple recommendation.

Single dwelling.....recommendation only

 

[Ian1981]

Single dwelling.....recommendation only

No it’s not , you should assess the merit of them being installed, they may not have to be installed but where does it say that they are only recommended?
Unlike the AFDD which clearly states ‘recommended’

 

[Markyd]

No it’s not , you should assess the merit of them being installed, where does it say that they are only recommended?
Unlike the AFDD which clearly states ‘recommended’

Wrong.....recommendation only...client says no then no

 

[Ian1981]

Wrong.....recommendation only...client says no then no

Right, I forgot that the client decides on what to install for an electrical installation.
show me where it says recommendation in the regulations?
Specifically the word ‘recommendation’

 

[Markyd]

Right, I forgot that the client decides on what to install for an electrical installation.
show me where it says recommendation in the regulations?
Specifically the word ‘recommendation’

Watch and learn...you should already know this 10mins in to vid apology accepted

View: https://youtu.be/iaK2zM7ynFU

 

[Ian1981]

It is a risk assessment with the client and based on your engineering judgment about the justification of installing such as device
It is still not a recommendation why can you not see that?
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Watch and learn...you should already know this 10mins in to vid apology accepted

View: https://youtu.be/iaK2zM7ynFU

Did he write the regulations on SPD’s?

 

[Markyd]

It is a risk assessment with the client and based on your engineering judgment about the justification of installing such as device
It is still not a recommendation why can you not see that?

Watch the vid it's not hard

 

[Ian1981]

Watch the vid it's not hard

Right well we are getting nowhere fast, enjoy your day