What this guide covers
This guide concerns homes in the Netherlands. British wiring diagrams, American tutorials and Belgian installation advice can describe different systems and requirements.
A light switch in the off position and a lamp that stays dark do not prove that the conductors are dead. Safe working requires suitable equipment, competence and checks at the work location. Two-pole tester instructions include verifying the instrument before and after use. Fluke: Dutch operating instructions. Stop if there is damaged insulation, moisture, loose equipment, unknown wiring or an absent protective connection required by the appliance. If there is smoke or immediate danger, move away from the danger and call 112.
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This guide concerns homes in the Netherlands. British wiring diagrams, American tutorials and Belgian installation advice can describe different systems and requirements.
Colours commonly found in Dutch homes
The following conventions are common in modern installations. Black and grey can also serve as phase conductors in a multiphase cable. Dutch cable manufacturer TKF describes that colour arrangement for a three-phase connection.
| Colour | Common purpose | What the colour cannot establish |
|---|---|---|
| Brown | Line or phase conductor | Whether the conductor has been connected correctly. |
| Blue | Neutral conductor | Whether it is safe to touch. |
| Green-yellow | Protective conductor, often called earth | Whether a sound earth connection exists. |
| Black | Switched line or a phase conductor | Which function it serves in this installation. |
| Grey | A phase conductor in a multiphase cable | Whether it can be used as a second neutral. |
At a ceiling light, the switched supply can therefore have a different colour from the line wire in the light's flex. Matching colours is not a reliable installation method.
The protective conductor has a specific safety function. It must not be repurposed to provide an extra switched connection.
Older wiring needs investigation
An older house can contain earlier colour systems alongside later additions. Previous work may also have used the wrong materials. A conversion chart showing an old colour beside a new colour cannot reveal what happened inside your particular walls.
Arrange an assessment where colours are unfamiliar, insulation looks brittle or the combination is unclear. Avoid pulling conductors out to trace their route. Existing drawings, inspection records and information about renovations can help an electrician establish the history.
A short piece of coloured tape also needs careful interpretation. NEN's public guidance warns against casually relabelling grey as blue to use it as neutral. NEN: questions about NEN 1010.
Prepare the information an electrician needs
- Record the make and model of the light, switch or appliance.
- Find its own installation instructions. Instructions for a similar-looking model may differ.
- Describe the job: replacement, relocation or an additional connection.
- Note what is visible without dismantling anything. Keep protective covers in place.
- Describe existing symptoms, including flickering, repeated tripping or any electric shock.
For example: “I want to replace a ceiling light. The new fitting is marked Class I, and I do not have a recent installation drawing.” This is more useful than asking which colour should connect to which terminal. It directs attention to the checks needed before installation.
Choose materials after the connection is understood
A Class I fitting needs the appropriate protective connection. A double-insulated Class II fitting uses a different protection arrangement. Do not choose between them by counting visible wires.
Connectors also vary. Even within one product family, conductor sizes and accepted conductor types can differ. The exact model determines whether solid or flexible conductors are permitted, the strip length, rating and enclosure requirements. WAGO's 221 information illustrates these differences.
Your preparation kit can be modest: a tape measure, appliance documents and a note of the proposed location. The actual connection determines the wire and connector quantities. Buying a screwdriver voltage tester does not establish that you can carry out the work safely.
Stop when voltage or earthing is uncertain
A light switch in the off position and a lamp that stays dark do not prove that the conductors are dead. Safe working requires suitable equipment, competence and checks at the work location. Two-pole tester instructions include verifying the instrument before and after use. Fluke: Dutch operating instructions.
Stop if there is damaged insulation, moisture, loose equipment, unknown wiring or an absent protective connection required by the appliance. If there is smoke or immediate danger, move away from the danger and call 112.
Frequently asked questions
Is a blue wire always safe to touch? No. Its colour does not establish its voltage or rule out a fault.
Can a photograph show which wire goes where? A photograph can explain the situation. It cannot establish conductor function, protective measures or the electrical condition of the circuit.
Should I buy wires and connectors in advance? Wait until the required type, cross-section and connection are specified. Visually similar materials can have different applications.
Ask CAS to assess the connection
If you would like the light or switch connected for you, send CAS Elektrotechniek a description of the job. Include model numbers and any installation documents you already have. Discuss your electrical job with CAS.
Sources
Materials and specifications
Before buying, check that the size, type and specification suit your installation. Use the article list and tools to work out the quantities you need.
Manuals and model details
- Quantity and unit
- One current manual per exact product
- Specification
- Use exact model/revision, with conflicting instructions unresolved until manufacturer/installer clarification.
Prepare an enquiry
Uncertain information stays unknown. This checklist gives no safety score and sends nothing. After checking, copy only what you want to share with CAS. In the event of fire or immediate danger, move to safety and call 112. Do not wait for a reply to a form submission.
Worked example and formula
Task: extra socket. Room: study. Supply: unknown. Request an assessment; the list does not approve an installation.
Checklist only; no safety score or automatic submission
Formula version 2026-10-05.1
Sources
Would you like CAS to carry out the work?
Tell us about the room, equipment and changes you need. Agree the work, checks and warranty terms before the job starts.
Discuss the workIn the event of fire or immediate danger: move to safety and call 112. Do not wait for a form reply.