Earthing ensures that fault current is safely diverted to ground. Together with the RCD, it forms the backbone of protection against electric shock (AREI Book 1, Part 4). An installation with poor earthing creates a false sense of safety.
The earth loop and earth resistance
In new construction, an earth loop is usually laid in the foundation trench, often as a bare copper conductor. The earth resistance must be low enough to keep touch voltage below the safe 50 V limit. With a general 300 mA RCD, that gives an indicative value of about 50 V / 0.3 A ≈ 166 Ω; in practice, you aim much lower and combine it with 30 mA protection.
Main and supplementary equipotential bonding
The main equipotential bonding connects all incoming metal pipes and exposed conductive parts to the main earth terminal: water, gas, metal drains, heating pipes and metal structures. In the bathroom, supplementary equipotential bonding also connects all metal parts to each other and to the protective conductors.
Indicative conductor sizes
| Part | Min. size (copper) |
|---|---|
| Earth loop (foundation earth electrode) | 35 mm² (bare copper) |
| Earthing conductor | 16 mm² |
| Main equipotential bonding | 6 mm² |
| Supplementary bonding (bathroom) | 2.5 mm² (protected) / 4 mm² (unprotected) |
How Voltuno helps
Correct earthing and equipotential bonding should be clearly shown on your single-line diagram. With Voltuno, you draw a correct single-line diagram, position diagram and matching bill of materials in minutes. Our software is built around AREI requirements, so you can work faster and prepare inspections 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.
