Earthing conductor size

This is a thermal withstand check only. It does not cover bonding conductor sizes, which prescriptive national rules set separately, and it does not check earth fault loop impedance, which is its own verification. Take the disconnection time from the device's time/current curve rather than the 0.4 s or 5 s code maxima, and if the protective device is current limiting, use the manufacturer's let-through energy I2t straight in place of I2t here. Have a qualified engineer confirm the final selection.