Vaillant 103429 sensor NTC (domestic hot water outlet pipe)

A Vaillant NTC sensor for ecoTEC VUW (condensing) and ecoTEC VUI (condensing) boilers. The sensor or thermistor decreases circuit resistance in line with temperature increases. A boiler's printed control board (PCB) sends a current to the thermistor, deciding whether a decrease or increase in heat is required by reading the relative resistance.