Rinnai K26i Thermistor The Rinnai K26i Thermistor - a vital bit of kit that keeps an eye on water temperature inside your Rinnai K26i continuous flow water heater. Without it, this key part of the appliance has no idea whether its getting hotter or colder - and that could spell disaster. To put it bluntly, thermistors play a critical role in keeping the burner running smoothly and stopping the water heater from getting too hot. If that sensor goes or starts producing dodgy readings, the water heater could be in for a bit of a temperature crisis - think temperature swings, wonky heating cycles, and error messages popping up on the dashboard. But replacing it with a genuine Rinnai K26i Thermistor gets things back on track and makes your water heater run like clockwork no problem. Made to the exact Rinnai specs you'd expect from a genuine part