Thorn Pump Overrun Stat 402S088 Apollo L165-10F

A pump overrun thermostat is a device used in heating systems to control the operation of the circulating pump after the boiler or heating system has shut down. When the thermostat senses that the boiler has turned off, it continues to run the pump for a short period to dissipate any remaining heat in the system and prevent overheating. This helps improve the overall efficiency of the heating system and reduces the risk of damage due to excess heat.