What is a Thermistor / NTC Sensor ?
The Thermistor is an electrical component whose internal resistance changes with temperature variation with one end exposed to the heat source, and the other is the electrical connection. The Thermistor can be used in several places around the boiler but are generally located on the flow or return pipes in the lower part of the boiler, inside the combustion chamber or attached to the heat exchanger outlet pipes. Some boilers have a flow and return thermistor, some also have a thermistor on the domestic hot water outlet pipe. The Thermistor can also be found checking the flue gas temperature on modern condensing boilers. Other names for the Thermistor are Temperature sensor or Negative Temperature Coefficient (NTC) Sensor. They can come as either a clip on sensor, push fit sensor or a screw fit sensor.