BoilerFaultCodesYour heat pump has stopped working because a sensor that monitors the temperature of the water returning to the outdoor unit has failed or detected an error.
Book a Gas Safe engineer within 24–48 hours. Your boiler may be unsafe or could break down completely if left.
Technical description: Outdoor Unit, Return Thermistor (Tw_in) Error
What causes this fault?
This fault occurs when the heat pump's control system loses a reliable signal from the sensor that measures water temperature coming back from your radiators. This is usually caused by a physical failure of the internal sensor probe or a loose connection in the wiring that carries the data. Without this information, the unit shuts down to prevent itself from overheating or running inefficiently.
Engineer required
This fault requires a Gas Safe registered engineer. Do not attempt gas-related repairs yourself.
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