What is the smallest size of conductor permitted for a feeder protected by a 175-Amp breaker in a residential service panel?

In residential electrical installations, the minimum conductor size for a feeder protected by a specific amperage breaker is critical to ensure safety and compliance with the National Electrical Code (NEC). For a feeder protected by a 175-Amp breaker, it's essential to select a conductor size that can safely carry the expected load without overheating, while also considering factors like the type of insulation and installation conditions.

The appropriate conductor size is determined by referencing NEC guidelines. For a feeder requiring protection by a 175-Amp breaker, the minimum permissible wire gauge is indeed 1/0 copper or 2/0 aluminum for typical applications. This size provides adequate current-carrying capacity while minimizing resistive losses and risks associated with overheating the conductors.

Using a larger conductor size, such as 2/0 or 3/0, would be permissible as they have a higher current-carrying capacity, but it’s not required. Thus, the selection of 1/0 is accurate for ensuring compliance with the NEC for a feeder circuit under a 175-Amp breaker, balancing both safety and efficiency.