BoilerFaultCodesGlow-worm F28 Fault Code
The Glow-worm F28 fault code means: your boiler has failed to ignite and is not receiving a steady gas supply or spark, meaning you currently have no heating or hot water.. It appears on 9 Glow-worm models in our database.
Technical description: Ignition fault
What causes the Glow-worm F28 fault?
This fault occurs when the boiler tries to light but fails three times in a row, leading to a safety shutdown. It is physically caused by a lack of gas reaching the burner or a failure in the ignition system, such as a worn-out spark electrode or a faulty gas valve. If you have a prepay meter, check that you have credit, as a lack of fuel is a frequent trigger for this error.
In extremely cold weather, this code can be triggered if the external gas regulator freezes or if there is a blockage in the condensate discharge pipe.
DIY fix possible
Check if your gas meter has credit (if on prepay)Ensure your gas stopcock and other gas appliances, like a cooker, are workingPress the Reset button (indicated by a flame icon with a cross) for five seconds
Find a Gas Safe engineer
Search the official register for a qualified engineer in your area.
Gas Safe Register →Glow-worm models that show the F28 fault code
Click a model for the full fault code list and model-specific repair notes.
Source
Glow-worm F28 fault code information on this page is sourced and cross-checked against the official Glow-worm service / installation manuals for each affected model.
Reviewed by the BoilerFaultCodes Editorial Team · Last reviewed 27 April 2026