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Hi There,

I've had my Leaf and a Rolec 7kW (not smart) charger for about a year - and I've not had any faults with my set up.

However - a few weeks ago, I was offered a Smart Charger as part of a trial. The engineers came out to fit it, and found that the resistance of the ground connection was too high (800Ω, instead of < 200Ω). They left my Rolec in place, but told me it was a risk to continue using.

Is this something I should actually be concerned about?

Cheers!
 

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Yes, I presume that you have an Earth spike fitted?
 

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Given the time of year I'm a bit surprised by that. Middle of a summer drought maybe, but January (and it's not been an especially dry winter).
As it's only a year in corrosion, etc, shouldn't be an issue.

Do you know how they measured it?
 

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On the assumption that your unit was fitted within the last three years and that the fitter claimed the OLEV grant then it will still be under guarantee and you should get them in to fix / rectify it ASAP. Sometimes Earth spikes are less than fully effective (hence why there are many ways of providing a safe Earth) and the installer should either fit another Earth spike or an alternative means of Earthing.

In terms of safety, in theory the outside of your car could become live if a fault develops and the unit might not trip due to the impedance, although at that figure it is very unlikely. The concern has to be that if the soil ever dries the figure will become higher and the risk will rise accordingly so get it fixed, particularly whilst it is under guarantee.
 

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However - a few weeks ago, I was offered a Smart Charger as part of a trial. The engineers came out to fit it, and found that the resistance of the ground connection was too high (800Ω, instead of < 200Ω). They left my Rolec in place, but told me it was a risk to continue using.
In terms of safety, in theory the outside of your car could become live if a fault develops and the unit might not trip due to the impedance, although at that figure it is very unlikely. The concern has to be that if the soil ever dries the figure will become higher and the risk will rise accordingly so get it fixed, particularly whilst it is under guarantee.
Provided the ground connection resistance does not rise much above 800Ω, and the circuit is protected by a 30mA RCD, there should be no safety risk - the old 16th Edition Wiring Regulations specified that the earthing (ground connection) resistance in Ohms multiplied by the RCD operating current in Amps should not exceed 50. 800 x 0.03 = 24.

However, the earthing resistance of an earth spike depends very much on the soil conditions (higher in dry summer weather, and lower in wet winter weather) so it appears that current regulations require at the time of test an earthing resistance of < 200Ω and preferably around 100Ω. Also, some Zoe's will refuse to charge if the earthing resistance is higher than about 140Ω.
 
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