If a circuit breaker is marked Al/Cu, what does this indicate?

• A. Copper conductors only
• B. Aluminum conductors only
• C. Not suitable for copper
• D. Aluminum and Copper conductors

Answer: (D)

Al/Cu on a circuit breaker means the terminals are listed for use with both aluminum and copper conductors. This allows you to land either type of wire on the lug, as long as you stay within the specified conductor sizes and torque. The marking reflects that the lug材料 and internal contacts are designed to work with both metals, which is helpful when field wiring involves different conductor materials. It’s not limited to copper or aluminum only, and copper is indeed permitted with this marking.