BoilerFaultCodesWhat the manual says
Manufacturer manualFault: Flow and/or return temperature sensor temperature change. When the burner starts, the temperature change registered at the flow and/or return temperature sensor is non-existent or too small. Insufficient water in product, Flow or return temperature sensor not in correct position at pipe
From this model's manual
Verified against the Vaillant/Vaillant Vaillantpro Ecofit Sustain Open Vent Installation And Servicing installation & service manual.
Engineer required
This fault requires a Gas Safe registered engineer. Do not attempt gas-related repairs yourself.
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All 36 fault codes on the ecoFIT sustain 430
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