UK Earthing a V2G Electric Car Charger with a earth rod

[ministrymason]

Hi I am new to the forum and looking for some advice.

I was supposed to have a vehicle to grid car charger installed last week. But they couldnt get a suitable earth from the earth rod. The earth rod reasing was 384 ohms. They're saying I need a marconite pit. the reading has to be below 100 ohms. Do i have any other options? I cannot use a matt:e box.

Would driving the rods deeper get it under 100 oms? a 8ft or 12ft rod? Or do I need a bentonite or marconite pit?

Any help appreciated.

 

[richy3333]

Use a Zappi charger and/or get someone qualified to install one. No issue with earth rods then. The cost of the proposed works will most probably be more than the extra for a Zappi!

 

[ministrymason]

I want to use the Vehicle to grid charger instead of a zappi charger. The V2G charger needs a earth rod. They have said they don’t have someone in my area who can install the earth rod. That’s why I’m asking for advice.

 

[Wilko]

Hi - I wouldn’t be too happy with that rod for use at my home and I’d be looking to understand 5e reading and improve it if possible. It might be a corroded connection for example (?). If you’d like some help with investigating and putting in more rods I’m sure someone here would be able to help you.

 

[pc1966]

Is the earth rod you are talking about an existing setup for your home, or one put in specially for the charger?

As Wilko says, its not very good as the IET guidance says above 200 ohm is suspect.

It could be a badly corroded copper clad rod (not likely if solid copper/brass of course) or you have very dry soil (unlikely recently!) or something strange is happening.

If it is due to the soil type, etc, then you can go deeper or put in more than one rod suitably spaced. Neither are linear (i.e. you need roughly 2.5 times rod length for half resistance) but are easy option.

Finally if putting in a new rod, or much longer one, check for pipes or cables first!!!

Background info for the interested (or bored):

Measurements and Calculations Of Earth Electrode Systems (BS 7430) | EEP

System earthing involves the provision of a connection to the general mass of earth. This connection should have a resistance not greater than that required to operate safety mechanisms to isolate the electricity supply from a fault situation.

electrical-engineering-portal.com

If looking for (major) utility pipes, etc:

Home - LinesearchbeforeUdig

LinesearchbeforeUdig (LSBUD) is a free internet based search enquiry system available 24/7 to make asset enquiries online with over 3 million enquiries per year

www.linesearchbeforeudig.co.uk

 

[ministrymason]

No sorry it isnt a current earth rod. The electritian, from the car charger company, tried to install an earth rod but got a earth reading of 384 ohms so he removed it.

 

[pc1966]

Where did he try fitting it, and any idea of what sort of soil conditions are there?

Bentonite clay is often used to help earthing rods:

Bentonite

Buy Bentonite online from AN Wallis; number one supplier of your earthing, lightning and surge protection needs. Buy now.

www.an-wallis.co.uk

We had a quote a while ago for something like £13 for 25kg bag, no postage mind! Still needs a source of moisture though, it works by keeping that close to rod I think.

 

[Strima]

What sort of soil do you have there? (sandy/gravel/clay etc)

Did he try installing the rod close to the building foundations?

Is your driveway fully paved or is there either grass or a flower bed close by where you can dig?

Rather than a rod you could lay tape in a trench or use conductive concrete (Marconite based). Conductive concrete isn't cheap at around £100 for a 25kg bag.

EV charger installation companies tend to have quite narrow profit margins and will not want to be messing around trying to get a good reading when they could be making money installing another unit somewhere else.

 

[pc1966]

Seems about £66 for 25kg before postage is considered for this brand:

Fursecem® Conductive Aggregate

Furse CEM conductive aggregate is designed to be added in place of sand and aggregate to cement to provide a conductive aggregate which lowers the resistance to earth

www.jointingtech.co.uk

 

[Gavin John Hyde]

Forget installing a rod and messing about with Marconite etc. Install one of these between the fuse board and charger. I install them on a lot of chargers in Somerset now as ground conditions or location make a rod not realistic. Simply route the supply through this box and you are good to go.

Single Phase EV Voltage Monitoring and Protection Unit

Built-in matt:e technology, which allows for the connection of 1 x 32A single phase charge point to the existing PME earthing facility

www.cef.co.uk

With the next generation of chargers and the current higher end models of chargers you can use PME and not have to worry about earth rods. more and more will go down this route as they update the model range.

 

[Midwest]

Forget installing a rod and messing about with Marconite etc. Install one of these between the fuse board and charger. I install them on a lot of chargers in Somerset now as ground conditions or location make a rod not realistic. Simply route the supply through this box and you are good to go.

Single Phase EV Voltage Monitoring and Protection Unit

Built-in matt:e technology, which allows for the connection of 1 x 32A single phase charge point to the existing PME earthing facility

www.cef.co.uk

With the next generation of chargers and the current higher end models of chargers you can use PME and not have to worry about earth rods. more and more will go down this route as they update the model range.

Is that one of those mythical box's of tricks, JW & E5 Group talks about

EV charging points 2020

I'm just interested in the technicalities of charging points, specifically with PME supplies, I know there's been a few threads on here, but I just wonder where we are with things currently. Someone posted this vid; View...

www.electriciansforums.net

 

[ministrymason]

Forget installing a rod and messing about with Marconite etc. Install one of these between the fuse board and charger. I install them on a lot of chargers in Somerset now as ground conditions or location make a rod not realistic. Simply route the supply through this box and you are good to go.

Single Phase EV Voltage Monitoring and Protection Unit

Built-in matt:e technology, which allows for the connection of 1 x 32A single phase charge point to the existing PME earthing facility

www.cef.co.uk

With the next generation of chargers and the current higher end models of chargers you can use PME and not have to worry about earth rods. more and more will go down this route as they update the model range.

I cannot use a Matt:e box with the V2g charger. If it was a pod point or zappi i could.

 

[Gavin John Hyde]

I cannot use a Matt:e box with the V2g charger. If it was a pod point or zappi i could.

How come? Be interested to know the reason?
[automerge]1584554274[/automerge]

Is that one of those mythical box's of tricks, JW & E5 Group talks about

EV charging points 2020

I'm just interested in the technicalities of charging points, specifically with PME supplies, I know there's been a few threads on here, but I just wonder where we are with things currently. Someone posted this vid; View...

www.electriciansforums.net

Yes, there are some 'concerns' about them but arguably no more so than exporting PME outside the zone. The regs permit it and the manufacturers now include it in some chargers.

 

[Midwest]

How come? Be interested to know the reason?
[automerge]1584554274[/automerge]

Yes, there are some 'concerns' about them but arguably no more so than exporting PME outside the zone. The regs permit it and the manufacturers now include it in some chargers.

Least if the rod is installed to specification, it will work as designed. Seems we are relying on manufacturers for these devices to work, with no way of knowing if they do.

Have you been sold a pup?

 

[pc1966]

Yes, there are some 'concerns' about them but arguably no more so than exporting PME outside the zone. The regs permit it and the manufacturers now include it in some chargers.

Is that not the main concern? The exporting PME under fault conditions is dangerous for something like a car that is bound to be touched.

Looking at those boxes it appears they are designed to isolate if the voltages look wrong as whatever amendment 1 will allow (no sign of any CT), but that is not a very reliable test without access to true earth (even high Z) or similar.

It might see hearsay, but using a 3-pole RCD (or ye olde ELCB design that actually measured earth current) to check for "external" earth current as well and so isolate the car completely (L, N & E) would make a lot more sense.

 

[westward10]

You are not exporting PME, PME stops at the source of supply. You are using a cpc which happens to be connected to a PME system. And what is this Zone you are exporting it out of?

 

[pc1966]

You are not exporting PME, PME stops at the source of supply. You are using a cpc which happens to be connected to a PME system. And what is this Zone you are exporting it out of?

Yes, your are correct in terminology.

The issue is the CPC could go to well over 50V under fault conditions (open CNE, imbalanced 3 phase load) and a car is located in a zone close to "true earth", which is exactly the situation that the IET guidance for caravans was designed to protect against.

For them it recommends a local TT supply (separate rod and 2-pole RCD). But a fancy RCD could cover all three conductors (L, N, E) but look for specific currents:

|L-N| > 30mA
|E| > 30mA

Neither should be present, but if any are they are then disconnect all 3. An L-E fault would show on both tests, a PME fault would show as E but only if someone touched the car, etc.

OK, you no longer have earth bonding after a disconnect and I guess that might be an issue of there is an alternative source of power, but it would cover both the EV and caravan cases.

 

[Gavin John Hyde]

Poor terminology on my part.
I dont necessarily agree with these devices, A company I sub contract for now insist on them , especially in the inner city installs or where bedrock makes the installation of a rod a non starter.
I accept they have limitations, not least on some of them a simulated or calculated reference to earth rather than a true measurement. its a big assumption to make in worse case scenarios. but the manufacturers stand by there product. AMD1 has permitted them.

 

[davesparks]

No sorry it isnt a current earth rod. The electritian, from the car charger company, tried to install an earth rod but got a earth reading of 384 ohms so he removed it.

How long was the rod? I assume there was only one?

If it was a single 1.2m/4' rod then there is not much chance of it ever achieving a suitable low reisistance to earth.

Personally as a bare minimum for an earth rod installation I would start with 2x 2.4m/8' spaced ideally 5m+ apart and then measure the resistance to establish what further work is necessary.

A single short rod, even if it is suitable initially, is unlikely to maintain a stable resistance to earth throughout the seasons.

 

[Strima]

How long was the rod? I assume there was only one?

If it was a single 1.2m/4' rod then there is not much chance of it ever achieving a suitable low reisistance to earth.

Personally as a bare minimum for an earth rod installation I would start with 2x 2.4m/8' spaced ideally 5m+ apart and then measure the resistance to establish what further work is necessary.

A single short rod, even if it is suitable initially, is unlikely to maintain a stable resistance to earth throughout the seasons.

I'm guessing not that long if he's managed to remove it. Used to have a hell of a job removing temporary electrodes when knocking down sites.