A PEN fault is a break — or a failing, high-resistance joint — in the supply conductor that carries both the protective earth and the neutral to a property. When it happens on a combined-conductor supply, the home’s earthed metalwork can drift up towards mains potential while every appliance keeps working normally. It matters for EV chargers because charging puts a person outdoors, on true earth, touching a large metal car connected to that earth for hours.
Key Takeaways
- A PEN fault is a failed combined earth-and-neutral conductor in the street supply — invisible in normal use.
- It can leave earthed metalwork — a car on charge included — at raised potential while everything appears to work.
- EV charging is the special case: the driver stands on true earth and touches the car, for hours.
- Protection is a design answer per property; a charger has it only if its specification says so — EVDANCE pages claim none.
The Conductor That Does Two Jobs
Most UK homes are fed by a TN-C-S supply, often called PME. In the street network, earth and neutral travel together on one combined conductor — the PEN conductor (protective earth and neutral). Inside the property they are separated, and from there they are the familiar separate earth and neutral. The arrangement is sound in normal service; the installer’s survey, not the householder, establishes which arrangement a property has.
What Happens When It Breaks
- The combined conductor fails upstream — a break, or a joint deteriorated until it barely conducts.
- The installation’s earth loses its reference — the network no longer holds it at true earth potential.
- Neutral current looks for other paths, and bonded metalwork — pipework, anything earthed, a car on charge — can be pulled up towards mains potential.
- Nothing announces it: lights, sockets and the charger keep working. An RCD watches for leakage where it should not be; here none needs to occur, so it may never trip. Our guide to RCD protection for EV chargers treats the two as answers to different faults.
Why EV Charging Is the Special Case
| Factor | Ordinary indoor appliance | EV on charge |
|---|---|---|
| Where the person stands | On the building’s floor, at the building’s own earth potential | Outdoors — grass, gravel, wet paving — at true earth potential |
| What they touch | An appliance earthed to the same system they stand in | A large metal car body held at the house’s earth, while the person is not |
| For how long | Moments of contact | Plugged in for hours, often overnight, with hand contact at plug-in and unplug |
| Warning signs | Usually none either | None — the session runs normally |
That geometry is why the wiring regulations and the IET Code of Practice for EV charging equipment installation ask EV installations a protective question ordinary socket circuits are not asked. It is also why the answer is designed in advance, per property: the published walk-through of one manufacturer’s answer — whether the Tesla Wall Connector has PEN fault protection — puts the question to the product’s specification, where answers of this kind live.
The Answers Are Design Answers
The responses sit in the installation design, in two families: detection that recognises the lost-PEN condition and disconnects the charge point, or an earthing arrangement for the charging circuit independent of the combined conductor. Which suits a property is the installing electrician’s decision, from the arrangement found at survey, recorded with the job, as part of what a standard installation includes. One honesty point: a charge point carries this protection only if its specification says so. EVDANCE’s pages do not claim PEN fault protection for any model — the EV-ACT3204PE wallbox (22 kW, three-phase Type 2, RFID and app, IP66, CE) is specified on those stated facts — so for a UK fixed installation the answer is placed by the installation design and confirmed in writing, not read off a listing.
Frequently Asked Questions
Can I test for a PEN fault myself?
There is no routine home test, and it is not a DIY diagnosis. If you ever get a tingle from metalwork or a car body, treat it as an emergency: stop touching it, keep others away, and call your network operator’s emergency line. Otherwise the subject belongs to the installer’s survey and design.
Does a PEN fault affect every UK home?
No — it is a property of supplies where earth and neutral arrive combined (TN-C-S). Other arrangements raise different questions. Your installer establishes your property’s arrangement; a neighbouring house is not evidence.
My charger has an RCD. Am I covered?
No — different faults. An RCD responds to current leaking where it should not; a lost PEN raises the earthed metalwork itself, without that leakage. A complete design records both separately.
Related Reading
- 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
- What Is a Standard EV Charger Installation?
- How to Become an Approved EV Charger Installer in the UK (OZEV)
