Low Information
S.11 on Glow-worm Ultracom sxi

Your boiler is performing a routine safety check by starting the fan before the burner ignites.

Reviewed by the BoilerFaultCodes Editorial Team · Last reviewed

Monitor it

This is a minor fault. Keep an eye on it and mention it at your next annual boiler service. Reset the boiler and see if it clears.

Technical description

fan pre-run

What causes this fault?

This is a normal part of the boiler's startup sequence where the fan clears any leftover gases from the combustion chamber to ensure a safe ignition. It is not a fault, but rather a status update showing that the system is preparing the burner to fire up. If this code stays on the screen without the boiler eventually firing, it may indicate that the fan is struggling to reach the required speed.

DIY fix possible

This fault may be fixable without an engineer. Check your manual first.

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Related fault codes

S.01View →S.02View →S.31View →

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