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General question as I try to raise my understanding of these things. Should an earth rod be connected directly to a chargepoint, or routed through a consumer unit and on to the chargepoint via 3-core SWA?
 

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If an electrician decided that an earth rod is needed to comply with the regs, then he would generally fit one and route the cable direct to the charge point, not the consumer unit, as the reason for using an earth rod is to have a separate earth to the one used within the house. Im sure the electrican doing the work can also explain their logic, especially if the job is an unusual install.
 

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As far as I'm aware it has to go directly to the charger and be isolated from the house supply earth.
Someone else may confirm.
Think it's to prevent any possibility of a fault back-feeding down the earth into the house wiring and electrocuting anyone in the house
 

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Directly to the charge point as suggested, and seperate from the PME Earth that that is normally used in the rest of the house that can float considerably above true Earth (it can be over 100 volts). If that is your only Earth you risk the body of the car floating to a similar amount. The oft quoted failure case is that if a child in flip-flops or with bare feet helps wash a car in such a case they could suffer a fatal shock.
 

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My wife and I are radio amateurs (Hams). When we had our house built I had it wired as 'TT'. This well worded explanatory leaflet explains why.

RSGB Leaflet

The reasons are the same as needed for EV charging outside.
 

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I installed my own home charger (Ohme) and installed the earth rod as part of that (with the assistance of an Electrician friend of mine). The earth rod connection goes to the earth of the charger, with the Live and Neutral going back to the consumer unit. Importantly, the earth from the consumer unit (house wiring) DOES NOT connect to the charger. My house is TN-C-S wired (earth connected to neutral at the supply, before entering the house) - this is the standard wiring for most UK houses (modern ones, anyway). The problem with this regarding EV charging is that an electric car is a large lump of metal, sitting outside on rubber tyres. If you're, let's say, washing your car when plugged in (WHICH YOU SHOULD NEVER DO!!!) you're connected to the car and to ground, via good conducting wet rags, shoes etc. Now if something happens at the supply (before it gets to the house) which disconnects the neutral (which is also the earth, remember) the car is now up at 240v and you're connected through the car to (real) earth. A probably fatal situation. The charger must be supplied from the consumer unit via an RCBO (residual current and over-current circuit breaker) but it may have trouble as the neutral and earth are both disconnected, so it may not detect the fault condition quickly enough. Therefore the earth rod gives the charger a seperate, good earth reference, in the same area of ground as the car is parked (and you are standing) so it can easily and immediately detect this fault condition and disconnect power before it kills you!
I should add this this kind of fault condition is very rare (although it has been known to happen) and you ALWAYS unplug your car before you clean it etc - don't you???
 

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Interesting. It seems they are actually backing away from recommending a TT installation, though an earth rod may still be needed to ensure reliable operation of some electronic protective devices (it wouldn't need the very low resistance of a TT).
 

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That's not how I read it.

Page 10
722.411.4.1 A PME earthing facility shall not be used as the means for the earthing for the protective conductor contact of a charging point located outdoors or that might reasonably be expected to be used to charge a vehicle located outdoors unless one of the following methods is used:
(it then goes on to list various devices including an earth rod and a MattE type device.)

Page 11
Note 6: Creating a TT earthing system for charging equipment or the whole installation as an alternative to using a PME earthing facility with one of the methods (i) to (v) above may not be an appropriate solution due to the inability to provide sufficient separation from buried metalwork connected to the supply PEN conductor.

So I read it that you can still use either route provided you take care to avoid the earth used with the TT from coming into contact with the earth (or worse) from the PME.

Glad that as usual it is as clear as mud, that there fails to be any discussion of the PME earth failing, and how any of the unicorn devices that fit under 722.411.4.1 should be tested / certificated.
 

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So I read it that you can still use either route provided you take care to avoid the earth used with the TT from coming into contact with the earth (or worse) from the PME.
Yes, you can use TT - but how will you demonstrate that your TT is not interacting with the PME?
If the charge point is 30m from any other supplied building then it's reasonable to say it's separated, but in the typical driveway next to the house installation it's going to be hard. In most cases it's a gamble as to what you might hit just driving the spike in - it could even end up grazing a supply SWA and be in contact with the armour :eek: .

I quite like their thinking. But it's obviously still a work in progress :)
 

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One option the wiring regs do not yet seem to have considered is to bury a metal mesh (? Concrete reinforcing mesh) under the car parking space and a reasonable area around it, and connect this (as well as the car charging point) to the PME earthing terminal, so as to drag the ground you are standing on when by your car up to PME potential. Should be cheap to provide if installed before the driveway is constructed. Also would have use in car park areas where obtaining a low earthing resistance in dry weather (? car park built on a waste slate heap) would be difficult.
 
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