| Phase Conductor Size (L) (Copper) | Protective Conductor Size (E) (Copper) | Condition / Note | | :--- | :--- | :--- | | | 1.5 mm² | Phase and Earth are typically the same size for small circuits. | | 2.5 mm² | 2.5 mm² | Standard for lighting and ring mains. | | 4.0 mm² | 4.0 mm² | Standard radial circuits. | | 6.0 mm² | 6.0 mm² | Cooker circuits, shower circuits. | | 10 mm² | 10 mm² | Sub-mains. | | 16 mm² | 16 mm² | Sub-mains. | | 25 mm² | 16 mm² | Transition Point: Earth can be half size. | | 35 mm² | 16 mm² | Earth remains 16mm² minimum here. | | 50 mm² | 25 mm² | Earth size is half of phase size. | | 70 mm² | 35 mm² | Earth size is half of phase size. | | 95 mm² | 50 mm² | Earth size is half of phase size. | | 120 mm² | 70 mm² | Earth size is half of phase size. | | 150 mm² | 95 mm² | Earth size is half of phase size. | | 185 mm² | 95 mm² | Check adiabatic equation for large faults. | | 240 mm² | 120 mm² | Minimum mechanical strength applies. |
Use this method for standard installations. earth cable size selection chart
If Aluminium earth conductors are used, the required cross-sectional area is larger to account for lower conductivity. Typically, for phase conductors ≤ 16mm², Al earth is not permitted; for larger phases, the Al earth size is calculated based on equivalent conductance to copper. | Phase Conductor Size (L) (Copper) | Protective
A chart for copper might not be accurate for aluminum conductors. Expert Tip: The Adiabatic Equation | | 25 mm² | 16 mm² |