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    Why Is My EV Charger Showing a PEN Fault / Voltage Drop Issues?

    Home — Blog — Why Is My EV Charger Showing a PEN Fault / Voltage Drop Issues?
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    Electric vehicles

    Electric vehicles (EVs) are becoming a common sight around Chelsea, and with that comes the increasing installation of home EV chargers. But if your charger suddenly shows a PEN fault warning or is experiencing voltage drop issues, it can be worrying especially if you’re unsure what it means or how serious it is. These are not minor technical glitches; they relate to your home’s earthing and supply voltage, and if left unresolved, they can pose risks such as electric shock or equipment damage.

    In this guide, we’ll explain what PEN faults and voltage drops are, why they happen, how UK wiring regulations (BS 7671) apply, and what Contact Electrician can do to diagnose and fix the problem quickly and safely.

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    What Is a PEN Fault?

    A PEN fault occurs when the Protective Earth and Neutral (PEN) conductor in a TN-C-S electrical supply becomes damaged, disconnected, or faulty. The PEN conductor carries both neutral current and provides the earthing protection for your property.

    If the PEN conductor fails:

    Your property may lose its safe earthing connection.

    Metal components in your EV charger or even your car could become live.

    There is a potential risk of electric shock.

    Most modern EV chargers are designed to detect this issue. When a fault is found, they display an error message such as “PEN fault detected,” “open PEN,” or “missing earth.”

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    Why Do PEN Faults Occur in EV Chargers?

    There are several reasons why your charger might detect a PEN fault:

    CauseExplanation
    Broken/loose PEN conductorIf neutral/earth connection is lost in the street supply or property.
    Corroded earth terminalsMoisture or ageing electrical installations cause poor connectivity.
    Overloaded supplyHigh electrical demand in the home can stress the neutral conductor.
    External damageRoadworks, underground cable faults, or weather-related incidents.

    As per BS 7671:2018 Amendment 2, EV charger installations must be designed to detect open PEN conditions and automatically disconnect the supply to prevent danger.

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    Understanding Voltage Drop Issues

    Voltage drop refers to a reduction in voltage between the electrical supply and the equipment (such as your EV charger). This can happen if:

    Cables are too long or undersized.

    There’s high resistance somewhere in the wiring.

    Your household electrical demand is too high.

    Voltage drop can contribute to PEN fault warnings because unstable voltage affects the neutral-to-earth voltage readings used by chargers for safety monitoring.


    How Voltage Drop and PEN Faults Are Linked

    The charger continuously monitors the voltage between live, neutral, and earth conductors. If voltage levels fluctuate excessively or the neutral becomes unstable, the charger assumes a PEN fault has occurred and shuts down for safety.

    For example:

    In Chelsea homes with older wiring, voltage drop is common during peak energy use.

    If the neutral connection is poor, the charger may detect a high earth-neutral voltage and trigger an alert.

    Warning Signs You Shouldn’t Ignore

    Look out for these common signs:

    Error message: “PEN fault detected” or “Voltage drop issue.”

    Metal parts feel warm or vibrating on your EV charger.

    Lights flicker or dim when the charger activates.

    Burning smell or buzzing from the consumer unit (fuse board).

    Charger stops mid-charge or disconnects frequently.

    If you notice any of these, stop using the charger and call a qualified electrician immediately.

    Are PEN Faults Dangerous?

    Yes. PEN faults can be extremely dangerous if ignored.

    Potential Risks:

    Electric shock from vehicle bodywork or charge cables.

    Fire hazards caused by overheating cables or connections.

    Damage to EV charger or car battery system.

    Void insurance or warranty claims if installed incorrectly.

    This is why BS 7671 regulations require EV chargers to detect PEN faults and safely isolate power.

    Stay Safe and Call a Professional

    A PEN fault or voltage drop issue is more than just an error on your EV charger screen it’s a serious electrical safety warning.

    If you’re experiencing this in your Chelsea home, Contact Electrician can help with expert testing, repairs, and compliance with BS 7671 regulations.

    Need help fast? Contact Electrician in Chelsea today to book an inspection or emergency call-out.






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