A single-line diagram is a language. If you know the symbols you read an installation in seconds; if you do not, you mostly see boxes and dashes. The signs are standardised, so every installer and every inspector reads the same drawing the same way.
Protective devices in the board
- Circuit breaker: a rectangle with the rated current (e.g. 16 A) and curve (B, C).
- RCD: a rectangle with the sensitivity in mA (30, 300) and the rated current.
- Main switch: at the top of the diagram, right after the meter.
- Fuse: still present in older installations, with its value noted.
Points in the home
Sockets are drawn as a half circle on a line; with an earthing contact they get an extra stroke. Light points are a circle with a cross. A plain switch is a tick on the line, a two-way switch has two positions, and an intermediate switch is recognisable by its cross. Dimmers and motion detectors have their own markings.
Cables and cross-sections
Next to every circuit line belongs the cable designation: the type (e.g. XVB or VOB in conduit), the number of conductors and the cross-section in mm². That way an inspector immediately sees whether the protection matches the cable — a 20 A breaker on 1.5 mm² is an instant remark.
Related reading
How Voltuno helps
Work from the right symbol library and you cannot pick the wrong sign. With Voltuno you draw a correct single-line diagram, position diagram and matching bill of materials in minutes, straight from your browser. The software is built around AREI requirements, so you work faster and walk into the inspection with a clear, complete file.
Please note: this article is a general explanation and not legal advice. Always consult the official, consolidated AREI text (FPS Economy) for the exact obligations and article references.
