BoilerFaultCodesFerroli A09 Fault Code
The Ferroli A09 fault code means: your boiler has sensed it is getting much too hot and has shut itself down to prevent damage or dangerous overheating.. It appears on 7 Ferroli models in our database.
Technical description: Overtemperature protection intervention
What causes the Ferroli A09 fault?
This fault occurs when the internal temperature sensors detect that the heat exchanger has exceeded its safety limit, causing the boiler to shut down to prevent internal damage. The most common reason is a lack of water flow, often caused by a failing circulation pump or a blockage within the system that prevents heat from being carried away. In some cases, it can also be triggered by a buildup of limescale or debris inside the heat exchanger itself.
This fault is more frequent in autumn and winter when the heating is first turned on, as pumps can seize up after being idle during the summer months.
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 A09 fault code
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Source
Ferroli A09 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