Lochinvar & A.O. Smith 100170487 Upper Sensor 321042-401 Includes the critical low-pressure switch

Includes the critical low-pressure switch to safeguard against fuel supply drops

Integrated Auxiliary Switch: The internal SPDT switch simplifies the wiring of end-stop verification or secondary equipment triggers

By choosing a genuine furnace heat exchanger replacement

Models include 5-1/2” sensing element

Lochinvar & A.O. Smith 100170487 Upper Sensor 321042-401 Includes the critical low-pressure switchThe Lochinvar & A. O. Smith 100170487 Upper Sensor (formerly TST1187) is a critical thermistor based component engineered for high precision temperature monitoring in residential and commercial water heaters. As a direct immersion NTC temperature sensor, it provides real time resistance feedback to the control board, ensuring the appliance maintains optimal setpoints while preventing dangerous high limit conditions. This OEM water heater sensor is