What is the ampacity of a 4/0 AWG THHN aluminum conductor connected to a 200-ampere rated circuit breaker?

The ampacity of a conductor refers to the maximum amount of electric current that a conductor or device can carry before sustaining immediate or progressive deterioration. In the case of a 4/0 AWG aluminum conductor using THHN insulation, the ampacity is influenced by various factors, including the type of insulation, ambient temperature, and the number of conductors bundled together.

For a 4/0 AWG aluminum conductor with THHN insulation, the ampacity is typically referenced from the National Electrical Code (NEC) tables. Under standard conditions, the ampacity for a single insulated conductor in free air is generally around 180 amperes.

When connecting this conductor to a 200-ampere rated circuit breaker, the purpose of that breaker is to provide protection against overloads and short circuits. However, the ampacity of the conductor itself does not exceed the rated capacity suggested by the NEC, even if the breaker can handle up to 200 amperes. Therefore, the most accurate choice provided regarding the ampacity for the 4/0 AWG aluminum THHN conductor in this setting is indeed 180 amperes, as that is in alignment with the typical ampacity value for that specific wire type and size. This information is crucial for