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How to read an electrical diagram?

Last updated on 29 April 2019

The electrical circuit diagram offers a clear overview of the entire electrical installation of a home. Which is why it must be presented as part of the inspection and certification of your electrical installation. It consists of two documents: a single-line diagram and a position diagram.

Although it may seem quite arcane to the uninitiated, it is worth making the effort to gain an understanding of electrical diagrams. It will prove a valuable source of information if you are having work done to your home or you are buying a new home, for instance.

What do the symbols in the electrical circuit diagram mean? 

The symbols used in the single-line diagram and the position diagram represent:

Do NOT try and be clever by inventing your own symbols: the RGIE (Règlement Général des Installations Électriques, i.e. the Belgian General Regulations for Electrical Installations) define exactly which symbols must be used.

The single-line diagram: the plan of your electrical installation

Unlike the position diagram, this diagram does not factor in the position of the electrical equipment in your home. 

A letter = an electrical circuit

The letters identify the basic electrical circuits that make up your installation.

Simply put, an electrical circuit is the part of the electrical installation that sits between two circuit breakers (except for the very last circuit downstream of the last circuit breaker).

Figures show the branch points

Inside every circuit, the branch points are numbered. The symbols identify the type of the respective branch points (sockets, electrical appliances, etc.).

The symbols

On the lines, symbols such as slanted lines, for instance, are used to include information about the type of wiring sleeves (recessed or surface-mounted), the number of conductors for each branch line, the manner in which they were fitted, etc. The protective devices, switches, and the junction or distribution boxes are also represented by symbols.

To give you an idea, check out this example of a single-line diagram on the website of the FPS Economy (in French)

The position diagram: the location of the electrical components in your home

The position diagram is easier to understand: it is a plan of your home carrying symbols which enable you to pinpoint every component of your electrical installation:

  • the distribution board
  • the junction or distribution boxes
  • the socket outlets
  • the light points
  • the switches
  • the electrical appliances

To give you an idea, check out this example of a position diagram on the website of the FPS Economy (in French)

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