What is the minimum THHN/THWN wire size required to serve a load of 47 amps, operating for about 5 hours at a time?

To determine the minimum THHN/THWN wire size required for a load of 47 amps operating for about 5 hours, it's essential to consider both the ampacity of the wire and the duration of the load.

The National Electrical Code (NEC) provides guidelines for the ampacity of different wire sizes based on their insulation type, temperature rating, and installation conditions. For THHN/THWN wire, the ampacity ratings vary with the specific installation scenario.

When considering a continuous load—defined as a load that operates for three hours or more—it's important to apply a derating factor to ensure safety and prevent overheating. For a load of 47 amps, which is considered continuous in this context, the calculation generally involves taking 125% of the continuous load to determine the required ampacity. This means we would calculate 47 amps multiplied by 1.25, which yields approximately 58.75 amps.

Referring to the wire size ampacity charts, a 6 AWG wire is rated for 65 amps, making it suitable for carrying this load when considering both the continuous nature of the load and the necessary ampacity. Therefore, the minimum THHN/THWN wire size required for safely serving a load