Which of the following correctly lists the minimum sizes for conductors by material?

• A. Copper 8 AWG; Aluminum 6 AWG
• B. Copper 6 AWG; Aluminum 8 AWG
• C. Copper 4 AWG; Aluminum 2 AWG
• D. Copper 10 AWG; Aluminum 8 AWG

Answer: (A)

The main idea is that the minimum size of a conductor depends on the material’s ability to carry current. Copper conducts more efficiently than aluminum, so to carry the same current safely, aluminum conductors must be larger in size than copper conductors. For typical limited-energy circuits with common insulation ratings, the smallest copper conductor that’s acceptable is 8 AWG, while the aluminum conductor must be 6 AWG to provide roughly the same ampacity. That’s why the pair copper 8 AWG and aluminum 6 AWG represents the correct minimum sizing. The other options either use copper sizes that are unnecessarily large or aluminum sizes that are too small to carry the intended current safely.