Open PEN Protection for EV Charging
Open-PEN protection is a supply-earthing safety assessment, not an optional charger feature to select from a marketing list.
A loss of the combined protective earth and neutral conductor on a PME supply can create dangerous touch-voltage conditions around an EV. The charging design must address this risk using an appropriate arrangement for the actual supply and installation.
This is practical guidance for competent electricians. Assess the actual installation, follow the current edition of BS 7671 and manufacturer instructions, and stop where the work cannot be completed safely.
Key takeaways
- Agree the scope and make the installation safe before starting work.
- Use a controlled sequence rather than relying on a single reading or visual assumption.
- Record the actual result, limitation or action taken while it is still traceable.
- Check the result against the design, protective measures and equipment instructions.
- Issue the appropriate certificate or report when the work is complete.
Scope the work first
A loss of the combined protective earth and neutral conductor on a PME supply can create dangerous touch-voltage conditions around an EV. The charging design must address this risk using an appropriate arrangement for the actual supply and installation.
Method
Identify the earthing arrangement, equipment capabilities and vehicle/charger installation context. Select and install the protective solution in accordance with current requirements and manufacturer instructions, then commission and test it as specified.
Doing this on a job? EV Charge Point Certificate — part of TradePlanr. Free to start, no card needed.
Checks and common pitfalls
Do not assume that every EV charger includes suitable protection or that a generic earth electrode solves every case. Verify the product documentation, connection arrangement, external metalwork and any special site conditions.
Record and hand over
Record the earthing arrangement, protective solution, equipment model, test evidence and client operating information in the EV commissioning record. Label the installation clearly for future maintenance.
Keep the evidence with the job
Record readings, limitations and remedial actions as you work. A clear certificate or report protects the client and makes the next visit easier to manage.
From guidance to action
Frequently asked questions
Does every EV charger on a PME supply need the same solution?
No. The appropriate arrangement depends on the charger, supply and site design. Assess the actual installation against current requirements and the manufacturer's instructions.
Can I rely on a standard rule of thumb?
No. The installation method, supply characteristics, equipment instructions and the current requirements all affect the correct decision. Use the guide as a workflow, then assess the actual job.
What should be recorded?
Record the scope, results, limitations, observations, remedial work and the certificate or report appropriate to the work carried out.
Related guides
EV Charger Installation: A Practical Guide
Surveying, cable sizing, earthing and certifying a domestic EV charge point installation.
Earthing Systems: TN-S, TN-C-S and TT Explained
How TN-S, TN-C-S (PME) and TT earthing arrangements work, and how to identify each on site.
EV Charger Cable Size Guide
Size an EV charging circuit from the design current, installation method, voltage drop and protective measures — not a rule of thumb.
