Earthing Rods for EV chargers

Second question first, as it is easier. You can add an earth spike in a parallel with any existing earthing system that you would be happy to bond a water main or a lamp post to - as far as the electrons are concerned it is the same.

On an EV charger there are two possible ways an electrode may be used either

1) in parallel with the supply earth to pull a local carrot of earth to the same potential as suppliers earth and the car body so it all moves together. 

2) As a TT island to pull the car body to the same potential as the local earth and the supply live and neutral can bounce about as much as it likes.

None of this matters a hoot, until the wheels come off with the supply cable or its joints  underground and the supply earth wiring is not at the same voltage as the terra-firma ground under your feet.  On a TNC-s system this is quite possible to raise the neutral and earth to a near-live voltage, while  on a TNS it is unlikely that the earth voltage will rise, but far more likely the fault loop impedance will rise.

The EV charge point may include some logic that disconnects the car (all poles including earth) if the electrode earth voltage and the supply one are more than say 20V apart. Not all do.

Mike.

Second question first, as it is easier. You can add an earth spike in a parallel with any existing earthing system that you would be happy to bond a water main or a lamp post to - as far as the electrons are concerned it is the same.

On an EV charger there are two possible ways an electrode may be used either

1) in parallel with the supply earth to pull a local carrot of earth to the same potential as suppliers earth and the car body so it all moves together. 

2) As a TT island to pull the car body to the same potential as the local earth and the supply live and neutral can bounce about as much as it likes.

None of this matters a hoot, until the wheels come off with the supply cable or its joints  underground and the supply earth wiring is not at the same voltage as the terra-firma ground under your feet.  On a TNC-s system this is quite possible to raise the neutral and earth to a near-live voltage, while  on a TNS it is unlikely that the earth voltage will rise, but far more likely the fault loop impedance will rise.

The EV charge point may include some logic that disconnects the car (all poles including earth) if the electrode earth voltage and the supply one are more than say 20V apart. Not all do.

Mike.