BoilerFaultCodesSaunier Duval F20 Fault Code
The Saunier Duval F20 fault code means: your boiler's internal computer parts are having trouble communicating with each other, causing the system to shut down for safety.. It appears on 6 Saunier Duval models in our database.
Technical description: Software incompatibility. Incorrect user interface or main board. Incorrect product code
What causes the Saunier Duval F20 fault?
This fault occurs when the boiler's internal control boards are unable to 'talk' to each other, often after a component has been replaced or due to a memory error. It physically happens because the software version on the main circuit board does not match the version on the display panel, leading the boiler to shut down as a safety precaution. The system effectively becomes confused and stops working because it cannot verify that the internal instructions are consistent across all parts.
Engineer required
This fault requires a Gas Safe registered engineer. Do not attempt gas-related repairs yourself.
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Gas Safe Register →Saunier Duval models that show the F20 fault code
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Source
Saunier Duval F20 fault code information on this page is sourced and cross-checked against the official Saunier Duval service / installation manuals for each affected model.
Reviewed by the BoilerFaultCodes Editorial Team · Last reviewed 27 April 2026