Reliable Temperature Sensing: The WT8840 water heater control from Resideo is designed for use in standing pilot applications using an immersion well for water temperature sensing. It is powered from a thermopile heated by the standing pilot flame. Includes an integrated NTC temperature sensor. The WT8840 series is the Water Heater Control for trade use to replace WV8840 valves used in A O Smith and Bradford White Water Heaters. It is designed for use in Standing Pilot applications using an immersion well for water temperature sensing. An included integrated NTC temperature sensor reads water temperature within the appliance up to 221 F [105 C].