BoilerFaultCodesIdeal 0U Fault Code
The Ideal 0U fault code means: your boiler is performing a routine safety check by blowing air through the system to clear any leftover gases before or after it fires up.. It appears on 1 Ideal model in our database.
Technical description: 15 seconds ventilation phase before or after operation of the unit
What causes the Ideal 0U fault?
This code appears when the boiler's fan runs to clear the combustion chamber of any residual gases, ensuring the unit is safe to ignite. It is physically triggered by the fan spinning up to create a specific airflow, which is then confirmed by the internal pressure sensors. While usually a normal operational step, if it persists, it could indicate that the fan is struggling to reach the required speed or the air pressure switch is failing to sense the flow.
DIY fix possible
Observe the display to see if the code disappears after 15-30 secondsEnsure there are no obstructions around the external flue pipeReset the boiler if the code remains on the screen for an extended period
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Gas Safe Register →Ideal models that show the 0U fault code
Click a model for the full fault code list and model-specific repair notes.
Source
Ideal 0U 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