BoilerFaultCodesGlow-worm F.28 Fault Code
Also written as F28 — same fault.
The Glow-worm F.28 fault code means: your boiler has tried to light the gas but failed, meaning it cannot provide heating or hot water until reset.. It appears on 6 Glow-worm models in our database.
Technical description: Ignition unsuccessful when starting up
What causes the Glow-worm F.28 fault?
This fault occurs when the boiler attempts to ignite the gas three times but fails to detect a flame. The most common reasons are a temporary interruption in your gas supply, a blocked burner, or an issue with the electrodes that create the spark needed for ignition.
This fault is more frequent during extreme cold spells, as external gas meters or pipes can sometimes freeze or experience pressure drops.
DIY fix possible
Check that your gas meter has credit and the isolation valve is openPress the Reset button (the flame symbol with a cross) for one secondCheck if other gas appliances in your home, like a hob, are working correctly
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 F.28 fault code
Click a model for the full fault code list and model-specific repair notes.
Source
Glow-worm F.28 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