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 of a THWN-2 grounded feeder conductor for a calculated neutral load of 85 amperes, it's essential to refer to the National Electrical Code (NEC) which provides guidelines for the sizing of conductors based on the ampacity tables.

For a continuous load like the neutral load in this case, the conductor must be sized at 125% of the load. Therefore, for an 85 amp load, the calculation would be:

85 A x 1.25 = 106.25 A

When checking the ampacity tables for THWN-2 conductors, you find that:

• A 6 AWG conductor typically has an ampacity around 65-75 amperes, depending on the conditions of use, which is insufficient for 106.25 A.

• A 2 AWG conductor can handle approximately 95 amperes, still not meeting the requirement.

• A 4 AWG conductor usually has a rating close to 85-95 amperes, which, again, does not meet the 106.25 A needed.

• A 1 AWG THWN-2 conductor has a higher ampacity, often rated at approximately 130 amperes in typical conditions, which exceeds the