This part detects if water is moving through the Saunier Duval boiler. If these switches are detecting water flow they can either be a pump proving flow switches or a domestic hot water flow switch which detects if a hot tap has been opened. All these Saunier Duval flow switches send signals to the printed circuit board within the boiler ensuring they are being monitored all of the time.
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Saunier Duval Flow switch platon 2000800136

Part: 2000800136

Price: £113.42
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Saunier Duval S5720200 Themaclassic Isotwin DHW Flow Sensor

Part: S5720200

Price: £39.27
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Saunier Duval S801189 SD30E Flow Switch

Part: S801189

Price: £32.43