Periodic inspection of EV charge points under NEN 3140

The guide on §722 — design requirements for EV charging installations covers how a charge point must be designed at installation: which RCD type, which earthing arrangement. This article covers what comes after that — the periodic NEN 3140 inspection of a charge point already in service, and why that inspection differs in several respects from that of a fixed, lightly used installation.

Why charge points call for a different approach

A charge point differs from a regular wall socket in two ways that matter for inspection frequency and depth:

Duty cycle and mechanical stress: a public or commercial charge point is connected and disconnected daily, sometimes several times a day. The charging cable and the plug connection therefore undergo considerably more mechanical cycles than a fixed connection, with corresponding wear on the strain relief, the locking mechanism and the enclosure sealing.
Exposure to weather: an outdoor charge point is continuously exposed to moisture, temperature cycling and UV radiation, which puts the IP sealing and the ageing of plastic components to the test faster than an indoor installation.

Additional checkpoints on top of the regular NEN 3140 measurement

Alongside the usual NEN 3140 checks (visual inspection, insulation resistance measurement, PE continuity, loop impedance), the following points deserve specific attention at a charge point:

RCD type and function: verify whether the RCD type present (or the combination of a type A RCD with an integrated 6mA DC-detection device per IEC 62955) still matches the design, and — for a type B RCD — whether the test was carried out with the correct multi-frequency test waveform (see the guide on type B testing).
Mechanical condition of the plug, cable and enclosure: visible wear, cracks in the cable jacket near the strain relief, play in the plug's locking mechanism, and damage to the IP sealing that could allow moisture ingress.
Locking function and communication between charge point and vehicle (where applicable): a charge point that does not properly terminate the charging session on disconnection, or that has a faulty lock, is a concern that a regular wall socket does not have.
Internal temperature/discolouration at connectors: visible discolouration or melt marks at the charging connector can indicate a poor contact that leads to overheating under repeated high-power (fast-charging) use.

Inspection frequency

As with other electrical work equipment, the frequency of the periodic NEN 3140 inspection is determined based on a risk assessment that accounts for duty cycle and environmental conditions — a public charge point with high usage and outdoor placement generally warrants a shorter inspection interval than a private charge point in a garage that is used only occasionally.

Practical relevance

When drawing up an inspection schedule for a charging hub or a commercial site with multiple charge points, it is important not to simply copy the inspection interval used for fixed installations: the combination of high duty cycle, mechanical plug connections and outdoor placement makes a charge point, in practice, a more vulnerable part of the installation than a fixed wall socket, and that warrants a correspondingly shorter inspection interval and a more extensive checklist.

Common mistakes

Placing charge points under the same inspection regime as a fixed, lightly used wall socket without accounting for the higher duty cycle and weather exposure.
Skipping the mechanical condition of the charging cable and plug because the electrical measurements (insulation resistance, PE continuity) come out fine on their own — mechanical wear on the strain relief or locking mechanism is a separate risk that an electrical measurement does not detect.
Testing a type B RCD with a tester that cannot generate the required multi-frequency test waveform (see the dedicated guide on this) — this gives a false sense of assurance about the DC-detection function.
Not accounting for the communication between charge point and vehicle during the inspection — a charge point that is electrically sound but where the locking or communication fails can still produce an unsafe or unreliable charging session.