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Discussion Starter #1
We had an independent installer do a site survey, and they said that earth rods aren't recommended any more, but instead some sort of special box (made by Matte) is used instead. In their quote, it was quite expensive.

Has anyone else heard of this? Are they talking through their hat, or are earth rods out of favour? When I emailed the MG-recommended Rolec supplier they said they'd probably put an earth rod in.
 

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Do you mean an Earth Mat?



More effective than a straight rod but require a big hole to bury them and as they contain upwards of 4 kg of copper cost a fortune in comparison.
 

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There's currently some amendments being made to the Wiring Regulations which are expected to allow the use of a voltage monitoring device, monitoring the supply voltage to protect against a lost neutral, which would avoid the need for an earth rod on PME installations. It's due for release shortly.


I think Zappi have a charger advertised as not needing an earth rod.
 

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Discussion Starter #4
There's currently some amendments being made to the Wiring Regulations which are expected to allow the use of a voltage monitoring device, monitoring the supply voltage to protect against a lost neutral,
That's it - that what this Matte box was doing. It went inside next to the supply, before the cable run out the to Rolec. Apparently using this is better than an earth rod...
 

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Ahh, the Unicorn device! The proposed Amendment 1 for BS7671 Section 772 Indent 4 no longer requires a TT Earth (such as an earth rod) but only requires measurement between the Protective Earth and the Neutral voltage coming in, and trips when it reaches an unsafe level which implies that the neutral could be 70 volts for more different from earth for than 4s and up to 5 seconds. However, that isn't safe in all cases according to MyEnergi as if there is a fault on the Protective Earth the measurement is false and it is possible for the Protective Earth to float way over 70 volts in comparison to true Earth without causing the trip. In that case the bodywork of a car connected to a charger could be a very high voltage and give a considerable shock to anyone touching it. Clearly MyEnergi have a better solution in the Zappi but are worried that the other devices are not safe.

Full details on this video

One question is why are sparkies being encouraged to go this new way? Answer fitting a hybrid TT Earth to a PME has always been a bit odd, but the major issue is that their insurance often doesn't cover them for the damage that they do to other utilities when knocking an earth rod in. I saw one worker make contact with a highly floating PEN on an 11kV cable when doing this and he received a nasty shock - but at least we could all laugh about it afterwards as if he's hit one of the lines he would have been toast.

So to the OP - stick to an Earth rod as long as you are sure that there are no utilities below where it is being fitted! The new regs will not be mandatory for a while yet and this way is cheaper and safer.
 

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Discussion Starter #7
So to the OP - stick to an Earth rod as long as you are sure that there are no utilities below where it is being fitted!
And if I'm not sure? I think it's actually pretty likely there would be utilities in that general area! At least a risk of all of electric, gas, water and sewage
 

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Looking at the Matt.e box referred to I can see the attraction to the sparky - it is quick and neat to install indoors and away from any groundwork.


At £150 it isn't too high a cost and will meet the amended regs when they are published, but I'm not convinced on the safety front.

You don't have to put the Earth spike by the charge unit, but it does probably mean a longer earth cable run to hide neatly.
 

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I've just ordered an Ohme charger install via smarthomecharge.co.uk (recommended on youtube) and they're quoting for an earth rod, so clearly they're still being used.
 

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Discussion Starter #10
Having looked at my house some more, I don't think an earth rod is going to be feasible. Do I understand that a Zappi is safer than the Matt:e box with a Rolec?
 

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Pity. Is there really nowhere that an Earth rod can be fitted within 5m of where you want the charge point?
The Zappi is to my knowledge the only fully safe option without an Earth rod.
 

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Hi all
Pod-Point don’t use rods and have the 6mamp bender installed (the “box” I presume the op is referring to.)

reg 722.411.4.1(iii)
 

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There's currently some amendments being made to the Wiring Regulations which are expected to allow the use of a voltage monitoring device, monitoring the supply voltage to protect against a lost neutral, which would avoid the need for an earth rod on PME installations. It's due for release shortly.


I think Zappi have a charger advertised as not needing an earth rod.
I’m pretty sure that it was covered in the new 18th edition.
 

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Having looked at my house some more, I don't think an earth rod is going to be feasible. Do I understand that a Zappi is safer than the Matt:e box with a Rolec?
If you want a rod fitting get someone to cat scan the area for you.
 

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Yes, but the voltage detection is already allowed and the change proposed is to make it the normal way. Whether it's safe is also the subject of debate. Personally I'm glad to have a TTE extension signed off under the previous regs.
 

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There's currently some amendments being made to the Wiring Regulations which are expected to allow the use of a voltage monitoring device, monitoring the supply voltage to protect against a lost neutral, which would avoid the need for an earth rod on PME installations. It's due for release shortly.
I’m pretty sure that it was covered in the new 18th edition.
No it wasn't - this a further, new amendment which has not yet been released, they were still consulting on it until end of 2019.
From what I understand the situation, the new 18th Edition required new charging points to either:
a) provide an independent (TT) earth for the car, or
b) have a device (could be incorporated within the charging point) monitoring the voltage between the PME Neutral/Earth and the general mass of earth (would require an earth rod) which will interrupt all the supply conductors (L, N, and E) to the car in the event of a voltage difference of greater than 70v for more than 4 seconds (must trip within 5 seconds), and which requires a manual reset.

At the time of issue of the 18th Edition, no such device was available for option B, but it would be a possible option for charging cars requiring a relatively low earthing impedance (eg. Zoes) in an environment where reliably obtaining a suitably low earthing impedance with an earth rod was difficult (eg. a car park built on slate quarry waste).

The object of the change in the Wiring Regulations is to avoid the risk of a dangerous voltage occurring between your hand (touching the car) and your feet (in contact with the ground) in the event of a break in combined Neutral/Earth wire of the incoming supply.
 

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The object of the change in the Wiring Regulations is to avoid the risk of a dangerous voltage occurring between your hand (touching the car) and your feet (in contact with the ground) in the event of a break in combined Neutral/Earth wire of the incoming supply.
That's what it fails to do. It does work if the phase positive floats more than 70 volts from the nominal 230, but only measured relative to the "Protected Earth Neutral" If there is a fault in the latter that could float up in line with an increase in the phase positive (hence not getting beyond the 70 volts differential that would trigger the device) but meaning that any devices with a metal case earthed to the PEN would be considerably above the truth Earth voltage and represent a significant shock hazard. The example used in the video was an EV in which the bodywork is at that voltage giving a shock risk which would be exaggerated by being washed (increasing conductivity between the car and the person and the person and the ground).
To me the other question is why is there a need to do this at all? It appears to be to avoid the need for the Sparky fitting an earth spike and the risks associated with installation and the lack of future testing.
 

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The device by MATT:E is called O:pEN (phase, earth, neutral) I'm guessing.
Spark saying it's safer is looking for an easy life.
It can also cause issues if the supply voltage rises above 253v. It shuts down the system until such time as it drops back down. Some may think that's a good thing but if it keeps your car from charging when you want it to then not so good.
I know your supply shouldn't get up there but that's not going to help. A dumb Rolec for instance will keep supplying.
 

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I have a stupid & naive question. Why can't the earth rod be connected to the PME earth? We have an attached garage with the meter cupboard inside it. Therefore the garage is within the equipotential zone. This is fine for charging the car inside the garage but if charging just outside on the gravel drive, either fails to comply with the 18th Edition or worse poses a risk of shock. The gravel drive is not insulated from the garage slab so why not treat as an extraneous conductive part?. In this case I can't see that hybrid TT system is a solution.
 
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