What is a main bonding jumper used for?

A main bonding jumper serves a critical role in ensuring the safety and reliability of electrical systems. Its primary function is to connect the grounding conductor to the supply-side bonding jumper, which helps to create a low-resistance path for fault currents back to the ground. This connection is vital for maintaining the integrity of the grounding system, reducing the risk of electric shock, and ensuring that protective devices like fuses or circuit breakers operate correctly in the event of a fault.

By linking these conductors, the main bonding jumper reinforces the grounding network of the electrical system, ensuring that all metallic components are at the same potential. This helps to prevent differences in voltage that can lead to dangerous shock hazards. In contrast, the other options do not accurately represent the purpose of a main bonding jumper, as they focus on functions like ungrounded circuits, circuit performance, or redundancy, which are not the primary objectives of a main bonding jumper.