BoilerFaultCodesIdeal F 0A Fault Code
Also written as F0A — same fault.
The Ideal F 0A fault code means: your boiler has detected that the water is flowing in the wrong direction through the pipes or that the temperature sensors have been installed on the wrong pipes.. It appears on 3 Ideal models in our database.
Technical description: Flow/Return Reversed
What causes the Ideal F 0A fault?
This fault occurs when the boiler detects that heat is rising on the return pipe faster than the flow pipe, suggesting the water is moving backwards. It is often caused by a failing internal pump that can no longer push water in the right direction or faulty sensors that are sending incorrect temperature readings to the control board.
This issue often surfaces when the heating is first turned on in autumn, as pumps can seize or become sluggish after being inactive throughout the summer.
Engineer required
This fault requires a Gas Safe registered engineer. Do not attempt gas-related repairs yourself.
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Search the official register for a qualified engineer in your area.
Gas Safe Register →Ideal models that show the F 0A fault code
Click a model for the full fault code list and model-specific repair notes.
Source
Ideal F 0A 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