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Discussion Starter · #1 ·
Apologies if this has been asked (and answered) already. I did try searching before posting.

I've now got five quotes for the installation of an Ohme wall charger in my garage. Three of the installers said it wouldn't need an earthing rod because of the location; two of them said it would. I'll get one if it's needed but is there a definitive yes or no answer to this?

Thanks. (y)
 

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LEAF N-TEC 62KW
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I'm installing one for my Lefanev charger.
I think the rod issue depends on which edition of the wiring regs the installer is following and possibly how your existing supply is earthed - i.e is it PME (TNC-S - DNO combines the neutral and earth) or TN-S (DNO provides a separate earth), or TT (DNO does not provide an earth so consumer needs an earth rod). My supply is via overhead cables and the DNO has not provided an earth so it is TT, therefore a separate earth rod just for the charger is recommended. (sometimes called Island earthing). If in doubt fit a rod but it should be close to where the charger is installed so that the distance between it and where you are when touching the vehicle and charging cable is as short as possible.
If your supply is TNS then the DNO earth is probably okay. If its TNC-S then I'd use a rod in the event there is a break in the DNO's neutral which would mean no earth either. (apart from from any earth bonding)
 

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If there is a PME label, then it is TNC-S (PME is the old name for this)
Shouldn't cost a lot extra for a rod, clamp and some 10mm earth cable (~£20 for parts)
 

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Discussion Starter · #9 ·
Understood. Thank you.

...which begs the question why have three of the installers said that the Ohme doesn't need an earthing rod? :unsure:

It's not about the cost - I'll obviously get whatever's needed. I'm just wondering why they haven't all said that it needs one.
 

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If the charger is inside the garage without the possibility of charging outside, what is the logic in having its own earth rod?
 

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If they have not done site visit then they should not have advised you either way in my opinion.
TT island earthing is common practice for EV charging equipment so a rod is neccessary, as it also is should the Ohme have a PEN device in it.
There are few things for them to consider such as risk of penetrating an underground service, other exposed metalworks, eg garage doors which are connected to the PME earth. It's easier not to fit one if they can get away with it...
The reason for the rod, is that it also earths the car so the ground between the rod and the car, and the car itself are all at the same ground potential.
If the earth is provided by a distant connection, or uses the neutral, then its possible for a potential to develop between someone touching the car and this distant earth. Hence the charger should have a local earth of its own.
In a PME supply, suppose the neutral broke just outside the property, the consumers current is now returning entirely through their earth bonded connections which will not provide a low enough resistance for safety. This means the car may not be at 0v but floating higher depending on the impedance of the earth bonding and hence could be a danger to anyone coming into contact with it.
 

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If the charger is inside the garage without the possibility of charging outside, what is the logic in having its own earth rod?
It's not then required.
It's a bit grey as the regs say something along the lines of "impractical" or "unlikely".
So if the charger is next to the door to the drive then it's quite likely to be used for a car stood outside and a rod or other solution is needed.
If it's at the back of the garage, then it's unlikely to be used on a car outside, so no extra needed (the car will be within the garage equipotential zone).
If it's part way down the garage ... it gets grey.
 

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But by that logic every appliance inside the house would require its own separate earth rod.
Hardly. (unless you live on bare solid floors prone to dampness)
Once plugged in, the car becomes a very large metallic appliance with no insulation between the ground and it, or the owner (or their children). Every contractor will have their own interpretations of the regs but why take extra risk for the sake of a few quid for a dedicated earthing rod.
In your case, personally. I'd lay rubber or PU matting on my garage floor.
 

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It's not then required.
It's a bit grey as the regs say something along the lines of "impractical" or "unlikely".
So if the charger is next to the door to the drive then it's quite likely to be used for a car stood outside and a rod or other solution is needed.
If it's at the back of the garage, then it's unlikely to be used on a car outside, so no extra needed (the car will be within the garage equipotential zone).
If it's part way down the garage ... it gets grey.
Yes can be a grey area but better safe than sorry.
 

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Yes can be a grey area but better safe than sorry.
That's subjective.
Rod needed.
Is incorrect. Additional protection is not always necessary and there are now alternatives where it is.

Regardless of how cheap a rod might be a lot of houses have areas where banging one into the ground is problematic for one or more of several reasons.
 

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That's subjective.
Is incorrect. Additional protection is not always necessary and there are now alternatives where it is.

Regardless of how cheap a rod might be a lot of houses have areas where banging one into the ground is problematic for one or more of several reasons.
May be, but the OPs question was why some installer said rod needed, and others didn't, presumably when none of them had done a site visit. When the work starts, they can then decide whether a rod is feasible and whether needed or not. I don't know whether the Ohme units include any extra protections such as a PEN device, or rcbo.
 

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This is nowhere near as simple as it appears. Particularly for the case of a charger in a garage where the 13A socket on the wall next to the EVSE is going to be PME it is not quite as clear (or as safe) as it seems just to put an earth rod in for the EVSE. In this case all you have done is to remove the risk of electrocution from a PEN fault from the car but shifted it to every other metallic item in the garage.
 

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Discussion Starter · #19 ·
Thank you all for the replies so far. Your knowledge and opinions are much appreciated. :)

None of them has done a site visit. They requested that I send them a video recorded on my phone, with me walking from the main consumer unit in the house, down the drive (where the meter cabinet is) to where I want the charger to be installed (the back wall of the garage). The ones that said I didn't need an earth rod gave as a reason the fact that the charger and car would always be inside the garage while charging. (I have no plans to ever run a charging cable outside the garage to charge a car on the drive.)
 

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Related question, I'm not clear if having the PEN-loss protection circuitry, combined with the 6mA DC fault protection circuitry, means you then don't need an Earth Rod. Here's my situation:

My dumb Rolec was fitted 6 years ago, before latest regs came in. It had no fancy protection circuitry, just the usual RCBO, and back at the extra mini-CU there's an RCD.

It's mounted inside gge, right by the up-and-over metal door, and charges the car on the brick-paved driveway as gge full of stuff.

I've upgraded the Rolec, and it now has the latest Viridian ECU (PEN-loss detection as standard now), with a new 1-pole Contactor to disconnect the Earth wire running down charging cable to the car, and it also has the (optional extra) 6mA DC fault detection device. So if either of these 2 "new" safety-circuits detects a fault, the original Contactor is opened & cuts of the L & N wires to the car, and the new 1-pole Contactor cuts off the E wire to the car. The only wire that will remain connected is the CP line, which in theory could have 250V AC on it, or even 400V DC if EV has gone bonkers, and this wire has something like a 1K Ohm resistor in series up at the ECU end.

My questions are,

1) do I still need an Earth Rod, on the basis my car's outside Gge zone?
2) Or have I put in sufficient "smarts" to make my setup sufficiently safe that I don't need one?
3) And if so, did I need both the PEN-loss and 6mA DC leakage devices to make it safe, or would the PEN-loss be enough on its own?

If this can be nailed down decisively, then I think we're probably very near to being able to come up with a set of diagrams, or maybe just a list, of what combinations of bits are/are not deemed "safe" by the experts here, for the various types of Earthing systems in the house, and the various places the EVSEs & Cars can be located.

Seems to me it must be possible to achieve this, and if the "deemed safe" combinations actually require more kit than the official Regs demand, then so be it. I for one am prepared to fork out a bit more cash to be safer, OTOH I don't want to have to smash up my gge floor or driveway to put an Earth rod in. I've survived 6 years without one so far...
 
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