The is a multiplier applied to a cable’s standard current-carrying capacity (ampacity) to account for environmental and installation conditions that hinder heat dissipation. Ignoring these factors is a recipe for insulation failure, fires, and costly downtime. The Core Concept: Heat is the Enemy Cables generate heat through I2Rcap I squared cap R
In a lab, cables are tested under "perfect" conditions—usually 30∘C30 raised to the composed with power C 86∘F86 raised to the composed with power F derating factor of cable