What size copper conductor is required for a branch circuit using type THHW 75C conductor installed in a raceway that contains not more than three current carrying conductors and drawing not more than 30 amps?

To determine the correct size of copper conductor for a branch circuit using type THHW (Thermoplastic High Heat Resistant Water-Resistant) insulation with a temperature rating of 75°C, it is essential to refer to the National Electrical Code (NEC) and the ampacity tables specifically for copper conductors.

For a branch circuit that carries a maximum of 30 amps and has no more than three current-carrying conductors, the NEC allows for a specific size of conductor to be used safely without exceeding its rated capacity. According to the NEC ampacity tables, a 10 AWG copper conductor is rated for 30 amps at 75°C. This means that a 10 AWG conductor can safely carry the load without overheating or being at risk of failure.

In contrast, a 12 AWG conductor would be insufficient for a 30-amp load, as its maximum rating at 75°C is only 20 amps. Using it for a 30-amp circuit would not comply with safety standards and could lead to overheating or fire hazards. The larger sizes, such as 8 AWG and 6 AWG, while they can carry more current, are not needed in this scenario where the load is 30 amps