When calculating wire fill, what is the percentage allowed for two wires according to the National Electrical Code?

The correct percentage allowed for two wires when calculating wire fill according to the National Electrical Code (NEC) is 31%. This value is derived from NEC guidelines which establish fill limitations to ensure safety and prevent overheating.

When wires are bundled together in a conduit, the space they occupy contributes to heat generation, and if the conduit is filled excessively, it can impede airflow and cooling. The NEC provides specific fill percentages based on the number of conductors in a conduit. For two conductors, 31% is the approved fill percentage to ensure proper heat dissipation and maintain safe operating conditions.

Understanding this concept is crucial for electricians and engineers to ensure compliance with electrical codes and maintain the safety and reliability of electrical installations.