For a 120/240-volt, 1-ph, 3-wire service to a 175-Amp service, what is the smallest grounded conductor that can be installed?

To determine the smallest grounded conductor for a 120/240-volt, single-phase, three-wire service rated at 175 amps, it's essential to refer to the National Electrical Code (NEC) tables, specifically Table 250.122, which outlines the minimum sizes of equipment grounding conductors based on the rating of the overcurrent protection devices.

For a service rated at 175 amps, the NEC mandates that the grounded conductor, typically made of copper, must be sufficiently sized to ensure safety and reduce the risk of overheating under fault conditions. According to the NEC guidelines, for a 175-amp service, the minimum size for the grounded conductor would commonly align with 4 AWG copper. This is because the standard practice is to select a wire size that's capable of adequately carrying the fault current without excessive voltage drop or heating, and the 4 AWG meets that criterion for the specified amperage.

This is why 4 AWG becomes the smallest allowed size for the grounded conductor in this scenario. The other sizes mentioned, such as 3/0, 2/0, and 1 AWG, exceed the minimum requirements, but are not necessary for a 175-amp service, as 4 AWG effectively provides the