Which copper electrical cable size should replace a No. 6 aluminum electrical cable?

When replacing an aluminum electrical cable with a copper one, it's essential to understand the ampacity differences between the two materials. Aluminum and copper have distinct conductivity properties, with copper being a better conductor. As such, a larger size of copper cable is required to match the same current-carrying capacity as a smaller aluminum cable.

For instance, a No. 6 aluminum cable typically carries a specific maximum current. To find the appropriate copper wire size that would safely handle the same load, adjustments are necessary due to the differences in conductivity. In this case, replacing a No. 6 aluminum cable would typically require a No. 4 copper cable along with considerations for factors like length and installation conditions to ensure safe and efficient operation.

Choosing a No. 6 copper cable would not be sufficient, as it would not have the necessary ampacity to match that of the No. 6 aluminum cable. Therefore, the correct answer should reflect that a larger size, specifically No. 4, is needed to appropriately replace a No. 6 aluminum cable with copper.