When installing EV chargers in the UK, one of the biggest compliance challenges is the earthing arrangement. Most domestic supplies use PME (Protective Multiple Earthing), which poses risks if the neutral is lost. Since the 18th Edition Amendment 2, every EV charger install must have a compliant PEN fault detection solution. This guide breaks down what PME compliance means, how to achieve it, and which products help you pass inspection the first time.
🧭 Jump to:
- Why PME Compliance Matters
- 18th Edition Rules for EV Installs
- How PME Fault Detection Works
- Approved Methods of Compliance
- Recommended PME Fault Detection Units
- FAQs
Why PME Compliance Matters
PME supplies are common across the UK, but they come with a hidden risk: if the neutral fails, exposed parts can become live. For EV chargers installed outdoors, that risk is multiplied - making compliance critical, not optional.
- PME supplies combine neutral and earth - if the neutral fails, touch voltages can rise to dangerous levels.
- EV chargers are classed as “outdoor equipment” - increasing risk when connected to PME.
- Non-compliance means failed DNO approval and potential callback costs.
18th Edition Rules for EV Installs
The latest wiring regulations (18th Edition, Amendment 2) leave no room for doubt. Every EV charger connected to a PME supply must have PEN fault protection in place - whether through rods or devices.
- Amendment 2 explicitly requires protection against open PEN faults.
- Earth rods were once the default solution, but they’re often impractical on modern sites.
- The regs now allow PEN fault detection devices as a compliant alternative.
How PME Fault Detection Works
PEN fault detection devices act as watchdogs on the supply. They monitor for a lost neutral, and the second dangerous voltages are detected, they cut power to keep the installation safe.
- Continuously monitors the supply for a lost neutral condition.
- Instantly disconnects the EV charger if touch voltages exceed safe limits.
- Some devices integrate load balancing and surge protection, reducing board space.
Approved Methods of Compliance
Installers have two main choices: earth rods or PME fault detection devices. Both meet the regs, but rods can be impractical on many sites, so most electricians now choose detection units or consumer boards with built-in protection.
- Earth rod installation (traditional, but time-consuming and site-dependent).
- Standalone PEN fault detection devices (mounted alongside consumer units).
- Consumer units with integrated PME fault protection (faster fit, less cabling).
Recommended PME Fault Detection Units
Check out our install-ready options:
- IP65 PME Fault Detection Unit with Load Balancing Relay
- PME Loss Consumer Unit with 40C RCBO + Surge Protection
- WMEPME12-LB PME Board with Load Balancing
FAQs
Still got questions? Here are the most common queries we hear from EV installers trying to stay compliant on PME systems.
Do all EV charger installs need PME protection?
Yes. Under the 18th Edition Amendment 2, all new EV charger circuits must include PEN fault protection if connected to a PME supply.
Can I still use an earth rod?
Yes, but only if soil resistivity and site conditions allow. Many installers now prefer PME fault detection devices as they’re faster, safer, and regulator-approved.
What’s the difference between standalone units and PME consumer boards?
Standalone units sit alongside the main board and only handle PEN fault detection. PME consumer boards integrate PEN detection, RCD/RCBO protection, and sometimes surge protection - saving install time and space.
Will these units pass DNO inspection?
Yes - all our PME fault detection units are built to 18th Edition standards and have been approved on domestic and commercial EV installs nationwide.
👉 Compare our full range of PME Fault Detection Boards and Units