Final answer:
The maximum overcurrent protection for a copper #10 RHW conductor under normal conditions is 30 amperes, which would need to be derated when the ambient temperature is 104°F; thus, it would be less than 30 amperes.
Step-by-step explanation:
The question pertains to the maximum overcurrent protection for a copper #10 RHW conductor when there are three conductors in a conduit and the ambient temperature is 104°F. As per the National Electrical Code (NEC), for copper #10 RHW wire under normal conditions (30°C ambient temperature) with three conductors in a conduit, the maximum overcurrent protection is 30 amperes. However, at an ambient temperature of 104°F (which is approximately 40°C), the maximum overcurrent protection must be derated. Without the specific temperature correction factors and conduit fill adjustment factors provided by the NEC tables, it is not possible to give a precise derated amperage. Nonetheless, we can say that it will be less than the 30 amperes allowed under normal conditions. Therefore, the most appropriate answer would be 30 amperes, and with understanding that in practice the actual limit after derating due to increased temperature would likely be a number lower than 30.