Cable Derating Factors ❲Must See❳

If a cable is run through thermal insulation (e.g., in a wall with fiberglass or in a ceiling void with insulation), the heat is trapped.

Understanding Cable Derating Factors: A Guide to Safe Electrical Design cable derating factors

For cables installed outdoors in direct sunlight, solar heating adds significant thermal load. If a cable is run through thermal insulation (e

Heat is the enemy of insulation. Every cable has a maximum continuous operating temperature (e.g., 70°C for PVC, 90°C for XLPE, 105°C for EPR). The cable generates heat due to resistive losses ($I^2R$). The surrounding environment also imposes its own heat. 70°C for PVC

The final effective ampacity is: