These NEMA combination motor starters with thermal overloads have fuses that blow if the connection experiences an electrical overload or short. They shut off power immediately if there is an electrical malfunction to protect high-current industrial equipment. Fuses are sold separately. Thermal overload relays, also known as heaters, prompt motor starters to break electrical connections with downstream equipment once a set temperature is reached. They are made of either bimetallic strips or solder-type materials and change shape as electrical current increases and temperatures rise. As the material changes shape, it opens and closes contacts that signal motor starters to disconnect power and prevent connected loads from overheating and causing damage.

These NEMA combination motor starters with electronic overloads have fuses that blow if the connection experiences an electrical overload or short. They shut off power immediately if there is an electrical malfunction to protect high-current industrial equipment. Fuses are sold separately. Electronic overload relays trigger motor starters to break electrical connections with downstream equipment once the current reaches a pre-determined range of full-load amperage. They have adjustable current settings and use semiconductors to monitor for overload conditions and trip once the current exceeds that set point. Electronic overload relays turn circuits on and off faster, are more accurate, and have longer service lives than thermal overload relays.

These NEMA combination motor starters with thermal overloads have circuit breakers that trip if the connection experiences an electrical overload or short. They shut off power immediately if there is an electrical malfunction to protect high-current industrial equipment and operators. Breakers are manually reset after they trip to resume normal operation. Thermal overloads, also known as heaters, prompt motor starters to break electrical connections with downstream equipment once a set temperature is reached to protect connected loads from overheating and causing damage. They contain either bimetallic strips or melting alloy solder materials. When the current exceeds a predetermined threshold and temperatures rise, the material bends or liquefies, causing the thermal unit to break the circuit and cause the motor starter to break its power contacts. As the materials cool down, they will return to their normally closed position and the circuit can be reset automatically or manually.