When replacing a conductor, what minimum size THHN copper conductor would you require for a 1 AWG aluminum conductor of equal or greater ampacity?

To determine the minimum size THHN copper conductor needed to replace a 1 AWG aluminum conductor while ensuring equal or greater ampacity, it’s essential to understand the ampacity ratings of both aluminum and copper conductors.

The ampacity of 1 AWG aluminum conductor is typically around 100 amps under standard conditions. Copper conductors, being more conductive than aluminum, have higher ampacity for a given size. According to the NEC (National Electrical Code), the ampacity for copper conductors is higher, which allows for a smaller size to manage the same amount of current.

For THHN copper conductors:

• A 2 AWG copper conductor has an ampacity of approximately 95 amps.

• A 3 AWG copper conductor has an ampacity of about 85 amps.

• A 4 AWG copper conductor is rated around 70 amps.

Considering this, the 4 AWG copper conductor has an ampacity that is less than the required 100 amps to match the performance of a 1 AWG aluminum conductor, making it insufficient for this application. Conversely, a 2 AWG copper conductor, while having slightly lower ampacity than 1 AWG aluminum, does not satisfy the requirement as you need a conductor