BoilerFaultCodesFerroli A11 Fault Code
The Ferroli A11 fault code means: your boiler has stopped working because it can no longer accurately measure the temperature of the water coming back from your radiators.. It appears on 3 Ferroli models in our database.
Technical description: Return sensor fault
What causes the Ferroli A11 fault?
This fault occurs when the internal control board receives an incorrect or missing electrical signal from the sensor that monitors water returning from your radiators. The most common reason is that the sensor has physically failed or 'drifted' out of its correct range, but it can also be caused by loose wiring or moisture damaging the sensor's connection.
Engineer required
This fault requires a Gas Safe registered engineer. Do not attempt gas-related repairs yourself.
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Gas Safe Register →Ferroli models that show the A11 fault code
Click a model for the full fault code list and model-specific repair notes.
Source
Ferroli A11 fault code information on this page is sourced and cross-checked against the official Ferroli service / installation manuals for each affected model.
Reviewed by the BoilerFaultCodes Editorial Team · Last reviewed 27 April 2026