BoilerFaultCodesSaunier Duval F29 Fault Code
The Saunier Duval F29 fault code means: your boiler has shut down because a safety component has detected that the internal temperature reached a level high enough to potentially damage the system.. It appears on 2 Saunier Duval models in our database.
Technical description: Thermal fuse. Replace the heat exchanger
What causes the Saunier Duval F29 fault?
This fault occurs when a safety sensor detects that the heat exchanger has reached an dangerously high temperature, often due to a lack of water flow or a buildup of debris. Because this component is designed to permanently break to protect the boiler from melting or catching fire, it means the system has suffered a significant overheat event. The most common reasons are a failed pump, a severe blockage in the pipework, or a lack of water in the system.
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 F29 fault code
Click a model for the full fault code list and model-specific repair notes.
Source
Saunier Duval F29 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