What is the minimum size copper equipment bonding jumper for a 40A rated circuit?

In the context of bonding for electrical circuits, the minimum size of the equipment bonding jumper is critical for ensuring the safety and effectiveness of the electrical system. For a 40A rated circuit, the National Electrical Code (NEC) provides guidelines on the size of the bonding jumper.

According to NEC requirements, the size of the bonding jumper is determined based on the size of the overcurrent protection device for the circuit. For a 40A circuit, the appropriate bonding jumper size for copper conductors is indeed 10 AWG. This size is sufficient to safely carry any fault current that may occur and ensure the integrity of the grounding system.

It's essential to adhere to these specifications because an inadequate bonding jumper can lead to dangerous conditions, such as potential electric shock, fire hazards, or equipment malfunction. Proper sizing ensures that in case of a fault, the bonding jumper can effectively connect all non-current-carrying metal parts, facilitating the proper operation of overcurrent protection devices and minimizing the risk of electrical hazards.

Therefore, for a 40A rated circuit, using a 10 AWG copper bonding jumper is the correct answer, as it meets the safety and regulatory standards outlined in the NEC.