What is the minimum size THWN-2 grounded feeder conductor required to supply an individual dwelling unit with a calculated neutral load of 85 amperes?

To determine the minimum size for a THWN-2 grounded feeder conductor supplying an individual dwelling unit with a calculated neutral load of 85 amperes, it is essential to refer to the National Electrical Code (NEC) guidelines, specifically Table 310.16.

For a dwelling unit, the size of the feeder conductor must be adequately rated to handle the continuous load, which is calculated based on the demand. In this case, a load of 85 amperes is specified.

When assessing the required conductor size, you should consider the typical ratings for copper conductors in a residential application. According to the NEC, a 4 AWG THWN-2 copper conductor is capable of handling a continuous load of approximately 85 amperes when considering the temperature rating and installation conditions. This means that a 4 AWG conductor is the minimum size that can safely deliver the stated load without overheating or causing other electrical issues.

Thus, the choice of 4 AWG for the feeder conductor matches both the calculated load of 85 amperes and the NEC recommendations for proper safety and performance, making it the correct answer.