How many equipment grounding conductors are typically installed between the main switchboard and Panel HB1?

The correct choice indicates that typically one equipment grounding conductor of 4 AWG is installed between the main switchboard and Panel HB1. This selection aligns with the National Electrical Code (NEC) guidelines regarding the sizing and number of grounding conductors necessary for proper electrical installation.

When assessing the grounding requirements, the NEC outlines that the equipment grounding conductor must be appropriately sized depending on the size of the feeder conductors and the overall system configuration. A single conductor that is adequately sized, such as 4 AWG in this case, is often sufficient to ensure the safety and protection of the electrical system, providing a reliable ground without excessive redundancy that may not comply with code requirements.

Having a single conductor minimizes potential points of failure while maintaining a low impedance path for fault currents, which is essential for the effective operation of protective devices and to enhance overall safety. Additionally, using a larger gauge conductor than necessary would not provide additional safety benefits and could be considered inefficient and unnecessary based on the load capacities and grounding requirements.