What is the ampacity of each current-carrying conductor in a 120/208-volt system using two "A" phase conductors, two "B" phase conductors, and two neutrals with 10 AWG XHHW copper?

In a 120/208-volt system where copper conductors are utilized, the ampacity can be determined based on the National Electrical Code (NEC) tables and considerations for the specific conductor type, temperature rating, and installation conditions.

For 10 AWG XHHW copper conductors, the base ampacity is generally around 30 to 40 amps under normal conditions, depending on factors such as ambient temperature and the number of conductors in a raceway. In this scenario, since there are multiple conductors (two phase conductors and neutrals), we must account for any adjustment or derating that is typically applied.

When two conductors are used, the ampacity for each conductor may be adjusted. Based on NEC Table 310.15(B)(16) for conductors rated at 75 degrees Celsius, the standard ampacity for 10 AWG copper is 40 amps. However, with the installation involving two phase conductors and two neutrals, it is essential to apply derating based on the number of conductors as specified in NEC Table 310.15(C)(1).

Considering these factors, the typical adjustment results in an effective ampacity for each current-carrying conductor being about 32 amps