What is the minimum size aluminum equipment-grounding conductor required for a feeder of four three-phase motors?

To determine the minimum size aluminum equipment-grounding conductor required for a feeder supplying four three-phase motors, one must reference the National Electrical Code (NEC) guidelines, specifically those pertaining to grounding conductors.

The NEC outlines specific sizing requirements based on the size of the amplifiers involved and the configuration of the equipment. For aluminum conductors, the general rule for sizing at least a grounding conductor is based primarily on the ampacity of the feeder conductors and the specific application. In scenarios where multiple motors are involved, considerations for the total capacity and individual motor ratings contribute to the calculations.

In this context, for aluminum conductors, typically, an equipment-grounding conductor would be sized following NEC Table 250.122. For feeders supplying motors, the grounding conductor must be sized to accommodate the total load.

A No. 4 AWG aluminum equipment-grounding conductor is often sufficient to ensure a safe and effective grounding path for several motors, providing adequate protection against potential fault currents. This size strikes a balance between safety and compliance, ensuring that if there's a fault, the grounding system can effectively manage the fault current without creating safety hazards.

Using a smaller conductor, such as No. 6 AWG or No. 8 AWG, could