What is the minimum size aluminum THWN grounded service-entrance conductor required for a single-family dwelling unit with a neutral load of 99 amperes?

To determine the minimum size aluminum THWN grounded service-entrance conductor for a single-family dwelling unit with a neutral load of 99 amperes, we refer to the National Electrical Code (NEC) guidelines, particularly focusing on the ampacity of aluminum conductors.

For a neutral load of 99 amperes, it is necessary to account for the continuous load requirements, which typically means sizing the conductor based on the actual load and applying a safety factor. According to NEC tables for aluminum conductors, the ampacity can vary based on the installation conditions—such as temperature rating and the number of conductors installed in a raceway.

Specifically, 1 AWG aluminum conductors are generally rated for a sufficient ampacity to handle the load of 99 amperes safely. This sizing also considers a safety margin for continuous usage. A 1 AWG THWN aluminum conductor is typically rated for 130 amperes or more under standard installation conditions, which makes it appropriate for this application.

The other sizes do not meet the requirements because they provide insufficient capacity when applied to a load of this magnitude, especially considering potential demand factors or load variations. The sizing of 1 AWG THWN ensures that the conductor maintains safety and performance standards for