What is the minimum size THHN copper conductor needed to replace a size 1 AWG TW aluminum conductor, ensuring at least equal ampacity?

To determine the minimum size THHN copper conductor required to replace a size 1 AWG TW aluminum conductor while ensuring at least equal ampacity, understanding the ampacity characteristics of both copper and aluminum conductors is essential.

Aluminum conductors typically have lower ampacity compared to copper conductors of the same size because aluminum has higher resistance. According to the National Electric Code (NEC), a size 1 AWG aluminum conductor has an ampacity of approximately 130 amperes when used in certain conditions.

Copper conductors, specifically THHN type, are known to have higher ampacity. For instance, a 4 AWG THHN copper conductor generally has an ampacity of around 85 amperes, while a 3 AWG THHN copper conductor can have an ampacity of about 100 amperes, which is still lower than the ampacity of a size 1 AWG aluminum conductor. In this context, while size 2 AWG copper may be used in specific applications, it usually does not meet the criteria either, as it has an even lower ampacity.

The correct choice, a 2 AWG THHN copper conductor, ensures that the ampacity exceeds or meets the requirement without compromising safety standards. Therefore