The Rheem-Ruud RTG20212BC Heat Exchanger Thermistor is a temperature-sensing component designed for compatible Rheem and Ruud tankless water heaters. It monitors heat exchanger temperature and changes its electrical resistance according to temperature variations, allowing the control system to regulate heating operation accurately. This thermistor helps maintain proper water temperatu... https://www.partshnc.com/rheem-ruud-rtg20212bc-heat-exchanger-thermistor