What is the minimum number of heaters required for a NEMA starter as per NEC for a specified motor circuit?

The minimum number of heaters required for a NEMA starter, as dictated by the National Electrical Code (NEC), is one. Heaters are critical components in overload protection systems for motors, as they are designed to sense the motor current and provide protection by tripping the circuit if the current exceeds a predetermined limit.

Having at least one heater ensures that there is a basic level of protection for the motor. This is essential for preventing damage from conditions such as overloads, which can lead to overheating and potential failure of the motor. The NEC stipulates this requirement to safeguard both the equipment and personnel.

While additional heaters may provide more precise protection depending on the specific application or motor size, the fundamental requirement begins with at least one. This ensures that the starter has the capability to protect the motor, making it an indispensable part of motor control systems.