The earthing arrangement of the supply decides which protective measures an EV charger installation needs. On TN-C-S (PME) supplies, installers must deal with the risk of a broken PEN conductor; on TT systems, the installation relies on a local earth electrode and residual current protection; TN-S is simpler but still needs correct RCD selection. For a three-phase wallbox like the EV-ACT3204PE, a qualified installer should identify the system and follow local wiring rules before connection.
Key Takeaways
- The earthing system determines the protection a charger needs.
- PME supplies need a solution for open-PEN faults.
- TT systems rely on electrode resistance and RCD protection.
- Installers follow national wiring rules and test before handover.
The Three Common Systems
| System | How earth is provided | Main EV charging concern |
|---|---|---|
| TN-S | Separate protective earth from the supply network | Correct RCD type and earth continuity |
| TN-C-S (PME) | Combined neutral and earth in the supply, split at the property | Open-PEN fault could make exposed metal live |
| TT | Local earth electrode at the property | Electrode resistance and reliable RCD protection |
Naming conventions and rules differ by country, so installers follow the national wiring regulations where the charger is installed.
Why PME Supplies Need Special Attention
On a TN-C-S supply, if the combined neutral and earth conductor breaks upstream, the earth terminal at the property can rise to a dangerous voltage. A car outdoors stands on the ground, so a person touching it could get a shock. Wiring rules in several countries require a solution, such as open-PEN detection built into the charger, a separate device, or converting the charging circuit to TT with its own earth electrode. Our articles on whether you need an earth rod and PEN fault protection explain the options.
What Installers Check
- Identify the earthing system at the supply intake.
- Measure earth fault loop impedance, or electrode resistance on TT.
- Select residual current protection that suits EV charging, including DC fault detection where required. See RCD types explained.
- Decide how open-PEN risk is handled on PME supplies.
- Check the three-phase supply is balanced enough and the cable is sized for 32 A per phase.
- Test and record results before handing over.
Information to Give Your Installer
Provide the charger’s installation manual and data sheet so the installer can see what protection is built in and what must be added. Ask EVDANCE for the latest documents for your exact model and market version. The IET Code of Practice for EV Charging Equipment Installation is a widely used reference in the UK and beyond.
About the EV-ACT3204PE
The EV-ACT3204PE is a hard-wired 22 kW three-phase wallbox at 32 A and 380 to 400 V, with a tethered Type 2 cable, RFID and app control, an IP66 enclosure and CE and RoHS marks. Installers should confirm which protective functions their market version includes before designing the circuit.
Frequently Asked Questions
What is the difference between TN and TT earthing?
TN systems take earth from the supply network; TT systems use a local earth electrode at the property.
Why is PME a problem for EV chargers?
A broken PEN conductor upstream can make exposed metal, including the car, live. Rules require a protective solution.
Can I check my earthing system myself?
An installer should identify and test it. Do not open the supply intake yourself.
Related Reading
- Do I Need an Earth Rod for My EV Charger?
- Does the Tesla Wall Connector Have PEN Fault Protection? (UK)
- RCD Protection for EV Chargers: Type A, Type B and 6 mA DC Detection Explained
- Can I Install a 22kW Charger at Home?
