BoilerFaultCodesEvo H9 Fault Code
The Evo H9 fault code means: your boiler has shut down because the exhaust gases have reached a temperature that is too high, which is a safety feature to prevent damage to the system.. It appears on 2 Evo models in our database.
Technical description: FLUE GAS OVERHEAT
Engineer required
This fault requires a Gas Safe registered engineer. Do not attempt gas-related repairs yourself.
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Evo models that show the H9 fault code
Click a model for the full fault code list and model-specific repair notes.
Source
Evo H9 fault code information on this page is sourced and cross-checked against the official Evo service / installation manuals for each affected model.
Reviewed by the BoilerFaultCodes Editorial Team · Last reviewed 7 July 2026