Wire Derating 🔥
Start with wire’s insulation temperature rating (e.g., 90°C THHN). Multiply ampacity by factor below.
In this setup, the wire—which is normally safe at 30A—is now only safe up to . Common Consequences of Ignoring Derating wire derating
At higher altitudes, air is less dense and provides less convective cooling, making it harder for wires to stay cool. The National Electrical Code (NEC) Requirements Start with wire’s insulation temperature rating (e
Running wires through conduits, insulation, or underground traps heat. đź“Ź Key Derating Factors The default current-carrying capacity () of a wire
Let’s say you want to run 12-gauge THHN copper wires through a conduit in a hot attic where the temperature reaches 104°F (40°C) .
The default current-carrying capacity () of a wire is calculated for ideal conditions—usually a single cable in open air. In reality, several factors hinder heat dissipation:
