According to NEC® requirements, what is the minimum number of heaters that can be installed in a starter for a motor?

The National Electrical Code (NEC®) provides standards for the safe installation of electrical equipment, including motors and their associated components. Regarding the installation of heaters within a motor starter, the code outlines specific requirements to ensure reliability and protection for the motor operation.

The minimum number of heaters that can be installed in a starter is 1. This is crucial because the heater serves to provide overload protection for the motor. Overload heaters are designed to operate in response to increased current draw, which may happen when a motor encounters resistance or binding conditions. If an overload condition occurs, the heater will heat up and eventually trip the motor starter, protecting the motor from damage due to excessive current.

Having at least one heater installed ensures that there is a baseline level of protection for the motor. While more than one heater might be installed for additional safety or for specific load conditions, the NEC requires that there be at least one functioning heater for effective protection. This aligns with safety practices and enhances the lifespan of both the motor and the overall electrical system.