Which NEC Table is used to size the conductor between the ground bar in a service panel and the metal housing of a 3-phase motor?

The appropriate NEC table to reference for sizing the conductor between the ground bar in a service panel and the metal housing of a 3-phase motor is based on the grounding requirements for equipment. Table 250.122 specifically addresses the sizing of equipment grounding conductors, which includes the conductors that connect the grounding bars or electrodes to all grounded equipment, such as a motor.

In this context, the equipment grounding conductor is crucial as it provides a low-resistance path to ground, ensuring safety and helping to prevent electrical shock or fire hazards in the event of a fault. By providing the correct size for the grounding conductor based on the rating of the motor, you ensure that the connection can handle potential fault currents effectively.

While the other options refer to different aspects of grounding and bonding—such as grounding electrode conductors, connections to grounding electrodes, or general grounding of specific installations—they do not specifically address the sizing requirements for the grounding conductor relative to the motor's protective measures as directly and appropriately as Table 250.122 does. Therefore, referencing this table ensures compliance with the NEC standards for equipment grounding, particularly for the application concerning a 3-phase motor.