Testing a wallbox: the guide for electricians

A wallbox is tested before it is first put into service, after every repair and at regular intervals. The aim is to show that it is electrically safe and switches off in the event of a fault. A normal socket-outlet measurement is not enough: without a connected vehicle, the wallbox does not put voltage on the charging connector. You therefore need a test adapter or a wallbox tester that simulates an electric vehicle.

How to test a wallbox in 6 steps:

• Visual inspection: check housing, charging cable, connector, supply line and labelling for damage.
• Measure the protective conductor: continuity and low resistance of the protective conductor (R_PE).
• Measure insulation resistance: between the live conductors and to PE (R_ISO).
• Check disconnection: loop impedance (Z_S) and residual current device (RCD or DC residual current detection).
• Check the function: simulate a vehicle, start charging, inject faults such as a protective-conductor interruption or a CP short circuit and check that the wallbox switches off.
• Create the test report: document measured values, limits, result and tester.

Testing is a job for a qualified electrician. This guide explains each step, the applicable standards, sensible test intervals and how to choose the right tester. It follows the German and European rules (DIN VDE, DGUV); the international equivalents are named where they exist.

There are three occasions: initial verification before commissioning, periodic inspection at fixed intervals, and testing after modification or repair.

Initial verification. Every newly installed wallbox is tested to DIN VDE 0100-600 (international: IEC 60364-6) before handover: inspection, testing and measurement. Only with the test report is the installation handed over with documentation.

Periodic inspection. In a commercial setting in Germany, the wallbox is part of the fixed electrical installation. Under DGUV Regulation 3, § 5, the employer must have it tested at defined intervals. The employer sets these intervals so that the installation can be used safely until the next test (BetrSichV § 3 (6)). The implementation guidance to DGUV Regulation 3 gives reference values:

The reference values apply to normal operating and ambient conditions. The electrician can set shorter intervals, for example for publicly accessible charge points with many users or in harsh environments. Manufacturers may specify different intervals for the RCD test button (DGUV, ETEM expert committee). The tables are reproduced in DGUV Information 203-050.

After modification or repair. After replacing components, changing the supply line or a fault, the wallbox is tested again. A test after major firmware updates is also sensible, because the charging behaviour can change.

Three sets of rules are central for wallbox testing: DIN VDE 0100-600 for initial verification, DIN VDE 0105-100 with DGUV Regulation 3 for periodic inspection, and IEC 61851-1 for charging behaviour.

Each connection point needs its own residual current protection of at most 30 mA. Two solutions are permitted: an RCD type B, or an RCD type A or type F together with DC residual current monitoring (RDC-DD) to IEC 62955. An RCD type B is therefore not always mandatory. The responsible standards body confirms this in the DKE FAQ on DIN VDE 0100-722 (questions 1, 4 and 6).

The electrical safety test comprises six measurements, made on the grid side (supply line) and the vehicle side (charging connector). The vehicle-side measurements only work with an adapter or tester that simulates a vehicle.

Device functions and standard references according to the Easy Chester Ultimate datasheet. The limits in the standard and the wallbox manufacturer’s data always prevail.

Grid side or vehicle side? On the grid side you test the installation up to the wallbox. On the vehicle side you test what reaches the charging connector, i.e. the protective measures through the wallbox. Only both sides together show whether a fault in the vehicle would be switched off safely.

The function test shows whether the wallbox charges correctly and switches off reliably in the event of a fault. A real vehicle is unsuitable because it cannot create faults deliberately. A wallbox tester therefore simulates the vehicle via the CP signal (Control Pilot) and the PP resistor (Proximity Pilot) to IEC 61851-1.

Vehicle states to IEC 61851-1. The wallbox recognises the vehicle state from the voltage on the CP line:

The nominal values apply with a tolerance. The charging station must keep them within ±0.7 V; the vehicle must accept values within ±1 V. A wallbox tester simulates the vehicle and therefore evaluates with ±1 V. It checks whether a vehicle would accept the value – this is not a conformance test of the charging station to the standard. Basis: DIN EN IEC 61851-1 (VDE 0122-1):2019-12, annex A (control pilot function).

Fault simulation. During an active charging session, typical faults are injected. The test is passed if the wallbox ends the charging session:

• Interruption of the protective conductor (PE)
• Short circuit on the CP line
• Short circuit or interruption of the PP line – only for wallboxes with a charging socket-outlet (type 2, case B to DIN EN IEC 61851-1). There the wallbox uses the resistance between PP and PE to detect whether a charging cable is plugged in and which current it may carry (annex B).
• Optional: insulation fault between one phase (L1, L2, L3) and PE with 2.5 kΩ, injected 5 seconds after charging starts

PP faults and tethered cables. If the wallbox has a permanently attached charging cable (case C), it does not need to evaluate the PP line: the PP contact in the connector is used by the vehicle. If such a wallbox continues charging during a PP fault, that is not a defect. With type 1 connectors to SAE J1772 (North America), the proximity contact with its latch switch mainly tells the vehicle that the connector is being released; whether a charging station also evaluates it depends on the device. In both cases the wallbox manufacturer’s data prevails.

Charging test. Finally, a real charging session runs. The tester measures voltage and current and shows the maximum charging power of the wallbox. This shows whether the configured charging current limit is correct.

More on testing without a vehicle: Testing a charging station without a real vehicle.

The choice depends on how many charge points you test and whether you only need to check the function or also prove electrical safety. There are three classes of device.

Easy Chester Micro as a wallbox tester. Easy Chester Micro from comemso belongs to the third class. It performs the safety tests on the grid and vehicle side: insulation resistance, protective conductor resistance, residual current protection, loop impedance, phase sequence and residual voltage. In addition there are fault simulation, charging test and communication testing to ISO 15118-2. The results go into a PDF test report rated PASS or FAIL.

If you also test DC charge points, choose Easy Chester Ultimate. It covers the same AC tests and adds CCS, CHAdeMO and NACS fast-charging points.

Without a report, a wallbox counts as untested. The report is the evidence for the operator, the accident insurer and the insurance company, and the basis for the next periodic inspection.

What belongs in it:

• Occasion: initial verification, periodic inspection or test after repair
• Operator, location and unique ID of the charge point
• Manufacturer, type, serial number and firmware version of the wallbox
• Type and rated current of the protective devices (fuse, RCD type)
• Result of the visual inspection, defects found
• All measured values with limit and assessment
• Result of fault simulation and charging test
• Tester used, with serial number and calibration date
• Overall result, date, name and signature of the electrician
• Date of the next test

Created automatically. Easy Chester Micro creates the report as a PDF with logo, address fields and comments. It contains the measured values with explanation, the communication steps, the maximum charging power and the MAC PLC address. The maintenance package adds the test location via GPS and photos of the visual inspection.

Checklist: a checklist for visual inspection, function test and measurements is included in our free guide to inspecting charging stations.

Most defects are not in the wallbox itself but in the installation in front of it.

• Wrong residual current protection: an RCD type A in front of a wallbox without DC residual current monitoring (RDC-DD). Only RCD type B or type A/F with RDC-DD are permitted.
• No separate residual current protection per charge point: DIN VDE 0100-722 requires an RCD of at most 30 mA for each connection point. One shared RCD in front of several charge points is not enough.
• Wrong phase sequence: on three-phase connections, a swapped phase sequence causes charging problems.
• Voltage drop on long supply lines: common for parking spaces far from the distribution board.
• Grid side only: without a vehicle-side measurement, it remains unknown whether the protective measures work at the charging connector.
• No fault simulation: the wallbox charges, but does not switch off on a PE interruption or CP fault.

Basis for the first two points: DKE FAQ on DIN VDE 0100-722, questions 4 and 6.

The cost depends on whether you hire a service provider or test yourself. Service providers usually charge per charge point plus travel; with several charge points at one site, the price per point falls. Framework contracts for periodic inspections are common.

For electrical contractors and operators with many charge points, an own wallbox tester pays off. The time per test is decisive: a device that handles measurements, fault simulation and report in one sequence saves several steps compared with an adapter, an installation tester and a manual report.

As a private person you may only press the RCD test button and check the wallbox for visible damage. Measurements on the installation are a job for a qualified electrician.

What you can do yourself:

• Press the test button of the residual current device regularly. If it does not trip, inform your electrical contractor immediately.
• Check the charging cable and connector for breaks, discolouration and scorch marks.
• Watch for error messages in the wallbox app or status display.

Looking for a wallbox comparison before buying? Product tests by consumer and automotive magazines help there. This guide is for professionals who test an installed wallbox.

In future, wallbox testing will also include digital communication. With the EU regulation AFIR, wired communication to ISO 15118 at AC charge points gains importance. It runs over power line communication (PLC) on the CP line.

The test checks whether the charge point establishes the PLC connection and runs through the communication sequence correctly. An important value is the attenuation from connection set-up to ISO 15118-3. Conspicuously high attenuation points to an impaired signal path.

Easy Chester Micro establishes communication to ISO 15118-2 with EIM authentication natively, without an external protocol converter. It documents the communication steps and the attenuation value in the test report. The extension to ISO 15118-20 is planned for Q1/2027. It does not replace a full AFIR conformance test; TLS-protected charging sessions are outside the scope of Micro.