BoilerFaultCodesGrant 429 Fault Code
The Grant 429 fault code means: your boiler is struggling to get enough fresh air to burn fuel safely, which usually means the permanent ventilation in the room or building exterior is blocked or insufficient.. It appears on 6 Grant models in our database.
Technical description: Vent E (cm²)
Engineer required
This fault requires a Gas Safe registered engineer. Do not attempt gas-related repairs yourself.
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Grant models that show the 429 fault code
Click a model for the full fault code list and model-specific repair notes.
Source
Grant 429 fault code information on this page is sourced and cross-checked against the official Grant service / installation manuals for each affected model.
Reviewed by the BoilerFaultCodes Editorial Team · Last reviewed 7 July 2026