The main bonding jumper is sized based on the size of what?

The main bonding jumper is sized based on the size of the service conductors. This is because the primary function of the main bonding jumper is to ensure a reliable electrical connection between the grounding system and the neutral conductor at the service equipment. The size of the main bonding jumper must be sufficient to carry any potential fault current that might flow through the system, and it is therefore proportional to the size of the service conductors involved.

When determining the appropriate size for the main bonding jumper, it is essential to refer to the NEC (National Electrical Code) guidelines, which specify that the jumper must be at least a minimum size based on the largest ungrounded conductor or the equivalent area of the ungrounded conductors. This sizing helps ensure that the jumper can effectively handle fault conditions, providing a safe and effective path for fault currents to ground, thereby minimizing electrical hazards.

The other options, while related to grounding and bonding, do not serve as the basis for sizing the main bonding jumper. Grounding electrodes, neutral conductors, and equipment grounding conductors have their own sizing requirements and functions, which are distinct from those of the main bonding jumper.