What is open PEN protection on an EV charger?
Open PEN protection detects specified faults affecting the combined protective earth and neutral conductor and disconnects the vehicle as designed. It addresses a shock hazard associated with protective multiple earthing (PME) supplies [S1]. IET guidance discusses protection under Section 722 of BS 7671 [S2]. Your electrical designer must confirm the method suits your supply and charging location. Checked October 2026.
What is open PEN protection?
Open PEN protection is a protective arrangement that detects specified faults involving a combined protective earth and neutral (PEN) conductor and disconnects the vehicle as required by its design [S1].
Why it matters for your site: a fault upstream of your premises can make connected vehicle metalwork hazardous relative to the ground, so the electrical design must address more than ordinary charging operation [S1].
PME means protective multiple earthing. The IET explains that PME use for outdoor charging depends on suitable protective measures [S2]. Ask your designer to confirm your actual supply arrangement.
Is it the same as an RCD?
A residual current device (RCD) and open PEN protection answer different protection requirements. The IET discusses RCD protection separately from the methods addressing PME charging hazards [S2]. A quote that says only “RCD included” leaves the open PEN design question unanswered.
Use the PME and TT earthing guide for the wider design choices. TT is an arrangement using an installation earth electrode; it also needs assessment of separation from PME-connected metalwork [S2].
Do not choose an earth rod or detection device yourself. Ask the designer to document the protective method and equipment evidence.
What should you check before handover?
Request the protected circuits, exact device, manufacturer instructions and commissioning evidence. Ask whether the method suits the supply phases. IET guidance identifies different device limitations and possible issues with island-mode operation [S3]. Tell the designer about planned solar or battery backup.
If an open PEN fault is detected, the IET says the distribution network operator (DNO), which manages the local network, should be contacted immediately [S1]. Obtain an agreed fault procedure for your staff.
Read choosing an installer and comparing quotes. Use the charging cost tool separately from safety specification.
Next step
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Common questions
What can cause a PEN conductor to break?
The IET identifies physical cable damage and corrosion among the causes [S1]. It is a network fault question for the relevant network company, rather than a reason to alter charger settings.
Does every EV charger need an earth rod?
No universal requirement follows from the cited guidance. The IET describes PME protective options and warns about separation when using TT earthing [S2]. Ask for the documented design for your installation.
Does a three-phase supply make every detection device suitable?
No. The IET describes methods with different supply-phase limitations [S3]. Ask the designer to match the protective method to the actual supply.
Can the same protection be assumed to work during a power cut?
Do not assume it. The IET identifies limitations for some detection devices in island-mode installations [S3]. Have the designer assess any battery backup arrangement.
Does an IET 01 claim establish statutory conformity by itself?
No. The IET states that IET 01 is not a designated standard and does not itself provide a presumption of conformity [S1]. Ask the designer for the relevant product and installation evidence.
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Sources
- IET 01 frequently asked questions, Institution of Engineering and Technology,Last checked 19 October 2026
- EV charging installations FAQs, Institution of Engineering and Technology,Last checked 19 October 2026
- EV charging installation earthing and protective device guidance, Institution of Engineering and Technology,Last checked 19 October 2026