Your boiler is currently running a standard safety procedure to clear out the internal air chambers before it attempts to ignite the flame.

Purgingthecombustionchamber,faninoperation

What causes this fault?

This status occurs when the boiler detects a need to clear the internal combustion area of any residual gases or debris before it can safely start the burner. It is a natural part of the boiler's safety protocol, triggered by the fan spinning at high speed to ensure a clean environment for ignition. This cycle is usually temporary and does not signify that a component has failed.