Baxi DHW Flow Sensor 720480801

The Baxi DHW flow sensor, part 720480801, is a thermistor-based sensor used on Baxi and Broag Remeha combi appliances. It sits in the domestic hot water circuit and reports temperature back to the printed circuit board. The thermistor's resistance falls as temperature rises, so the board reads the changing current and decides whether the appliance needs to increase or reduce heat output. It is listed under the spare part group Thermostats, Thermistors & Sensors.

• Domestic hot water runs hot then cold, or the outlet temperature drifts away from the set point
• The appliance does not recognise a hot water draw-off and stays in heating mode
• Boiler locks out or displays a fault code relating to the DHW sensor
• Hot water production becomes intermittent, with the burner cutting in and out
• A resistance check across the sensor reads outside the expected range for the measured water temperature

• Check the GC number and appliance model against the compatibility list before ordering, as the same appliance family uses several sensor variants
• The earlier number S59133 may be stamped on the part being replaced, so confirm this matches the unit fitted
• This part is fitted to a gas appliance; installation must be carried out by a Gas Safe registered engineer.