A 400-Amp switch using three 4/0 AWG conductors requires what minimum size EGC to the motor?

For a 400-Amp switch using three 4/0 AWG conductors, the minimum size equipment grounding conductor (EGC) can be determined based on the requirements outlined in the National Electrical Code (NEC). When calculating the size of the EGC, one must consider the current-carrying conductors.

According to the NEC, for a circuit with a conductor size of 4/0 AWG (which typically carries up to 230 amps), an EGC is usually sized according to Table 250.122, which provides specifications based on the rating of the overcurrent device.

In this case, with a 400-Amp overcurrent device, the required EGC size must meet or exceed the requirements stipulated in the NEC for larger ratings of conductors. The EGC for a 400-Amp rating is generally 2 AWG copper, which offers adequate grounding capability. This would highlight that a size of 4/0 or 6 AWG would not meet the standards required for grounding under these circumstances.

Thus, when assessing the choices provided, "none of these" is appropriate because none of the listed options align with the minimum size EGC requirement for a 400-Amp switch connected to 4/