Earth Rod explanation
What is an EV earth rod/electrode and do I need one?
An earth rod (or electrode) is a typically a conductive rod of steel or copper driven into the ground and connected to an EV chargepoint. This connection helps to protect the user from potentially lethal electrocution should the electricity distribution system supplying the property develop a fault. This is commonly known as “loss of the Protective Earth and Neutral (PEN) conductor”.
However, driving earth rods is time-consuming, expensive, and can be dangerous if you accidentally hit water mains or sewerage pipes laying below. Equally, installing near to underground pipes, or other metallic objects above ground (outside taps, lighting, metal cladding) that are connected to the house earthing system (known as a PME, or Protective Multiple Earth system) could actually make the installation more dangerous.
In 2020, the Institution of Engineering and Technology (IET) and the British Standards Institution (BSI) introduced Amendment 1 to the 18th Edition IET Wiring Regulations to regulate standards for installing EV chargers without earth rods if one of the exceptions mentioned in the regulations is met.
New generation EV charging units, including SyncEV BG, have been developed to allow installation without the need for an earth rod, whilst fully complying with the 18th Edition regulations.
But how does this system work?
SyncEV BG chargers feature an on-board safety monitoring device to detect low or high voltage supplies and potential earth-neutral faults (this is in accordance with British wiring regulations for single phase supplies). If a fault condition is encountered the EV charge cycle is ended or prevented and the charger indicator goes red to show a fault. The charger isolates the power to the vehicle which effectively poses no risk to touch. This feature removes the requirement for an earth electrode where it may be ineffective or introduce further risk.
The technical bit for installers:
SyncEV BG chargers feature an on-board safety monitoring system to detect low or high voltage supplies and potential earth-neutral faults, this in accordance with regulation 722.411.4.1 (iv) of BS7671 2018 (Compliant on single phase supplies only). If such a condition is encountered the charge cycle is ended or prevented and the charger indicator goes red and effectively becomes a double insulated (class II) device. The vehicle becomes isolated from incoming supply and poses no risk to touch. This feature removes the requirement for an earth electrode where it may be ineffective or introduce further risk. The charger may be connected directly to a TN-C-S (PME) earthing system without any special arrangements. It remains the responsibility of the installer to conduct a risk assessment of the immediate area to a range of 10 Meters (equipotential zone) to ensure no other conductive metal fixings pose risks (mixture of TT/TN-S and TN-C-S), this is important where cable length may enable charging inside or outside of a building/ garage where the vehicle is within touching distance. Where certain conditions dictate an earth electrode must be used it shall be independent from the distributors earth system with no direct interconnection (the incoming supply SWA protective earth should be isolated from the housing and/ or earth electrode). The electrical installer shall install a suitable electrode complete with termination housing and covers where appropriate, warning labels should be visible and close to the unconnected SWA protective earth e.g. inside the charger.
The earth connection shall be made from the electrode to the charger via copper conductor earth wire of an appropriate CSA for the installation. The earth wire shall be installed in conduit where there is a risk of mechanical damage or UV exposure. Additional note: SYNC EV recommend Earth electrode impedance to be <100ohms