What is the minimum size circuit conductor needed for Motor #4 as indicated in Figure 230.271?

To determine the minimum size circuit conductor required for Motor #4, it is essential to refer to the National Electrical Code (NEC) and consider factors such as the motor's full-load current, the type of service, and any applicable derating factors based on installation conditions.

In this situation, the choice of 12 AWG as the minimum conductor size suggests that the motor's full-load current rating falls within the capacity limits of this gauge. Typically, a 12 AWG wire can handle up to 20 amps under standard conditions, making it suitable for smaller motors or applications where the full-load current of Motor #4 does not exceed this rating.

The choice also indicates adherence to NEC guidelines that aim to prevent overheating and ensure safe operation of the electrical system.

In contrast, other conductor sizes such as 8 AWG, 10 AWG, and 6 AWG are larger and capable of carrying higher currents. They may not be necessary if the motor does not require that additional capacity. Selecting a larger gauge when a smaller one suffices can add unnecessary cost and complexity to the installation. Thus, 12 AWG is the minimum required for the safe operation of Motor #4 based on the provided parameters.