Given: A 120/208 volt, three phase, 4 wire WYE connected transformer secondary supplies the following dwelling unit load: 120/208 volt single phase. No 208 volt loads. Ungrounded service conductors that are sized 1/0 AWG type THW aluminum. What minimum size THW aluminum conductor can be used for the grounded service conductor to this dwelling unit?

Given: A 120/208 volt, three phase, 4 wire WYE connected transformer secondary supplies the following dwelling unit load: 120/208 volt single phase. No 208 volt loads. Ungrounded service conductors that are sized 1/0 AWG type THW aluminum. What minimum size THW aluminum conductor can be used for the grounded service conductor to this dwelling unit?