BoilerFaultCodesIdeal Tw_Out Fault Code
Also written as TWOUT — same fault.
The Ideal Tw_Out fault code means: your heat pump has stopped working because a sensor that measures the temperature of the water leaving the outdoor unit has failed or is disconnected.. It appears on 1 Ideal model in our database.
Technical description: Outdoor Unit, Flow Thermistor (Tw_Out) Error
What causes the Ideal Tw_Out fault?
This fault occurs when the heat pump's control system loses the signal from the sensor that monitors the temperature of the water exiting the outdoor unit. The most common reason is that the sensor has developed an internal electrical failure, or its connecting wires have become damaged or corroded due to exposure to the elements. Without this data, the system cannot safely regulate heat production and shuts down to prevent damage.
Engineer required
This fault requires a Gas Safe registered engineer. Do not attempt gas-related repairs yourself.
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Gas Safe Register →Ideal models that show the Tw_Out fault code
Click a model for the full fault code list and model-specific repair notes.
Source
Ideal Tw_Out fault code information on this page is sourced and cross-checked against the official Ideal service / installation manuals for each affected model.
Reviewed by the BoilerFaultCodes Editorial Team · Last reviewed 27 April 2026