Engineers typically use a rule of thumb for current density: Aluminium: ~0.8 A/mm². Copper: ~1.6 A/mm².
(Coating Factor): Accounts for whether the bar is bare, painted, or sleeved. Painted bars often have better heat dissipation. indal handbook for aluminium busbar hot
The "hot" rating is derated by altitude and ambient temperature. For every 1°C above 35°C ambient, you must derate the current carrying capacity by approximately 1.5% to 2%. Engineers typically use a rule of thumb for