The Baxi thermistor works by decreasing current resistance in a manner that is inversely proportional to the temperature of the thermistor. The printed circuit board sends a current to the thermistor and can tell whether a decrease or increase in heat is needed by the resistor.
Comes with O-ring and fibre washer
Technical specification
Manufacturer Model No720480801Brand NameBaxiCompatible WithAvanta Plus Combi 24c, Avanta PlusCombi 28c, Avanta PlusCombi 35c and Avanta PlusCombi 39c