Integrated PEN fault protection for Zaptec Go (UK 7kW open PEN fault version)


The Zaptec Go (UK 7kW open PEN fault version) has integrated PEN fault protection. This article describes this feature.



The integrated PEN fault protection complies with BS 7671:2018 Amendment 1:2020 clause 722.411.4.1 (iv). An independent test report is available to confirm this; see the attachment to this article. 

The PEN fault protection is triggered if the charger detects a voltage of more than 253 V rms or less than 207 V rms between the line and neutral conductors for more than 5 seconds.

When triggered, the live, neutral and earth connections to the vehicle will be disconnected. The charger will display a red light:

Red light go charger.jpeg

If charging is in progress, it will be stopped.

After the charger detects normal voltage for 30 seconds, it will return to normal operation.

If it is not charging, it will return to ready mode (white light).

If it is charging, it will resume charging (blue pulsing light) up to ten times before locking out permanently. To reset this lockout state, disconnect the charging cable. The charger will then return to normal operation once it has detected normal voltage for 30 seconds. 


What should I do if a PEN fault is detected?

PEN fault detection means that an abnormal supply voltage has been detected that is outside of the statutory requirements. This is a potential safety hazard, and so must be reported to the Distribution Network Operator (DNO) by the owner by dialling 105.

The DNO should then investigate the reason for the abnormal supply voltage and make repairs, if necessary.

Additional diagnostic information is available from the charger to help with any investigation. This information can be requested by contacting Zaptec support


Why is PEN fault protection necessary?

In the UK, it is a legal requirement that EV chargers that are used to charge vehicles outdoors are protected from neutral faults when connected to a PME network. This ensures that the user cannot get an electric shock if the supply neutral becomes disconnected. This is done by disconnecting the live neutral and earth connections to the vehicle if a fault is detected, in accordance with IET wiring regulation 722.411.4.1.

This is because many UK electricity supplies combine the earth and neutral into one Protective Earth-Neutral (PEN) conductor, using a supply system known as PME (Protective Multiple Earth). Normally, this is a safe system. It becomes unsafe if the PEN conductor becomes disconnected (or "open") from earth. During this state, if someone simultaneously touches something connected to the PEN conductor (such as an EV plugged in to a charger) and something at true earth potential (such as a metal fence), the usual earth-leakage protection RCD will not operate - and the person could receive a fatal electric shock. To protect against this, it is necessary to either provide a dedicated earth to the EV charger, or fit a PEN fault protection device that will automatically disconnect the PEN.

If there is a true earth available (TT or TN-S) and the earthing system is in good order, PEN fault protection may not be required. If there is any doubt, then PEN fault protection must be fitted. 


App behaviour

If the PEN fault protection operates, this information is shown in the Advanced settings screen of the relevant charger:

Abnormal supply voltage detected.jpeg


Identification and electrical connections

The Zaptec Go (UK 7kW open PEN fault version) can be easily identified by the "ZGBxxxxxx" serial number.

It has three connections: Live, Neutral and Earth (PE).

Wago connection closeup.pngWago connection drawing go .png


Can integrated PEN fault protection be configured or disabled?

The integrated PEN fault protection cannot be configured or disabled.



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