Before you look at the chart, you must understand why the sizes are chosen. According to international standards, the cross-sectional area (CSA) of the earth conductor must satisfy two conditions:
Before diving into the selection chart, it's essential to understand the factors that influence the choice of earth cable size: 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. Before you look at the chart, you must
If the path back to the transformer is very long, the resistance might be too high for the breaker to "see" the fault. A thicker earth cable reduces this resistance. If the path back to the transformer is
the earth wire unless you have performed the Adiabatic calculation to prove it can handle the thermal stress.
For standard domestic installations, charts often recommend the following minimum sizes for main bonding: Main Supply Conductor Min. Earth Bonding Cable Typical Application Small homes, apartments Standard family homes Large homes / heavy loads Pros:
If you want to save money on copper or are working on industrial projects, you use a specific formula to see if a smaller wire is safe. S: Minimum cross-sectional area ( mm2m m squared I: Fault current (Amps). t: Operating time of the protection device (Seconds).