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Discussion Starter · #1 ·
Had Bp pulse 7 Kw charger installed outside to charge my Kia Soul.
I was expecting to have an Earth Rod installed to provide a separate Earth for the charger that would be separate from the TN-S Earth supplied for the rest of my house electrical system.
However the BP electrical contractor said that my installation would be using a new system incorporating a new RCD in a separate box.

I did point out that should there be a problem with my incoming Distribution cable being damaged, I felt that this “new system” wouldn’t make it safe if someone made contact with the car during a fault in the supply cable outside of my property. He replied that it was completely safe and I shouldn’t worry.


I’m inclined to disagree as I’ve since received the NIC EIC Installation certificate which shows a couple of mistakes in his box ticking exercise. I told him before he started that there was a Gas Earth ground but that the incoming water mains pipe didn’t have an Earth Ground connection because from the water meter, all internal pipes are plastic, with the exception of some copper pipes within the area of the new Combi boiler but they then transition to plastic.
My concern is that this New RCD won’t give me the protection that a properly installed (separate from the Distributors TN-S Earth) Earth Ground Rod system would give me.
I understand the use of these new RCD’s are now being used to get around the need for installing Earth Rods and the problems installing them can cause, but I still feel that Earth Rods give better protection for people using external EV chargers.
What thoughts do you have?

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What you have been provided with meets the 18th Edition First Amendment regs. I personally agree with you that an Earth rod is safer but a lot of people don't pointing out that they sometimes are less effective when the surrounding ground dries out. The key is that you are protected from a floating neutral in the event of a TN-S fault by the Boyce LXCVR-EV unit and its associated contactor.
 

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I do not have an earth rod. My electrician, who I trust and is an EVSE installer for one of the networks, pointed out that he could see the earth conected to the incoming sheath plus bonding to the metal gas pipe and stated that they were much more reliable than a bit of copper rod hammered into the dry sand by the garage door. If I was out in the country linked to the grid with overhead cables i might worry about earthing but as it is I am less than 25 metres from the substation.

It is worth noting that almost all the pages on supply faults can be traced back to suppliers of alternative earth protection devices. One bit of information I have unsuccessfully searched for is what percentage of these supply faults are relevant to ordinary small scale domestic installations. I have a suspicion that these faults are very rare in normal housing (because the cable runs are mostly short and protected) and likely innocuous (because the phases are unlikely to have widely differing loads).

I am not saying that there isn't a risk, just that as with all things in life you have to balance your personal likelihood of encountering the hazard. It's probably much safer just to get your electrics checked every few years rather than to loose sleep over the details of your EVSE earth.
 

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Discussion Starter · #4 ·
What you have been provided with meets the 18th Edition First Amendment regs. I personally agree with you that an Earth rod is safer but a lot of people don't pointing out that they sometimes are less effective when the surrounding ground dries out. The key is that you are protected from a floating neutral in the event of a TN-S fault by the Boyce LXCVR-EV unit and its associated contactor.
Thanks, I did look at this RCD and what it provides in the way of protection and so was looking for other peoples views on this device, considering it’s relatively new for EV Charger installations.
Thanks for your input.👍🤗
 

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Discussion Starter · #5 ·
I do not have an earth rod. My electrician, who I trust and is an EVSE installer for one of the networks, pointed out that he could see the earth conected to the incoming sheath plus bonding to the metal gas pipe and stated that they were much more reliable than a bit of copper rod hammered into the dry sand by the garage door. If I was out in the country linked to the grid with overhead cables i might worry about earthing but as it is I am less than 25 metres from the substation.

It is worth noting that almost all the pages on supply faults can be traced back to suppliers of alternative earth protection devices. One bit of information I have unsuccessfully searched for is what percentage of these supply faults are relevant to ordinary small scale domestic installations. I have a suspicion that these faults are very rare in normal housing (because the cable runs are mostly short and protected) and likely innocuous (because the phases are unlikely to have widely differing loads).

I am not saying that there isn't a risk, just that as with all things in life you have to balance your personal likelihood of encountering the hazard. It's probably much safer just to get your electrics checked every few years rather than to loose sleep over the details of your EVSE earth.
Thanks for your reply👍
I posted the question because I’m not an electrician and was looking for other’s opinions on the issue, which you have provided. 🤗
Thanks for your reply.
👍
 

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I spent a bit of time looking at this and the general conclusion seems to be it’s a fairly over the top requirement as the risk of a fault is small. That said it seem almost the only “safe” solution is a huge earth pad making up the foundations of the driveway or house. A single earth rod is almost never going to really do much worth having and the risk it presents to other services in the ground when banging it in isn’t trivial. These pen fault protection devices are not guaranteed to work in the event of a genuine fault, for reasons I can’t remember, but they satisfy the requirements and everyone seems happy.

I went for an evse that has this functionality built in, as many do now.
 

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Please just trust your electrician, its much more complicated than it seems and an earth rod is not the necessarily the safest solution. To quote from the IET website "...installers have increasingly adopted a TT earthing arrangement to comply with Regulation 722.411.4.1 of BS 7671. The installation practices for this approach have not always achieved an improvement in safety. "
 

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If its TN-S, there is surely zero risk from a floating neutral... You dont even need that box on a TN-S system.

The Floating neutral problem occurs in TN-C-S supplies, where the household earth is derived from the neutral terminal at the main fuse.
 

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If its TN-S, there is surely zero risk from a floating neutral... You dont even need that box on a TN-S system.

The Floating neutral problem occurs in TN-C-S supplies, where the household earth is derived from the neutral terminal at the main fuse.
TNS installations are often converted to TNCS over time and quite possibly are TNCS upstream (in the street) oven if it doesnt appear so in the house.

Regs are the same for any TN system.

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