BoilerFaultCodesGlow-worm F29 Fault Code
The Glow-worm F29 fault code means: your boiler was running but the flame has unexpectedly gone out, causing the system to stop working as a safety precaution.. It appears on 9 Glow-worm models in our database.
Technical description: Flame loss during operation
What causes the Glow-worm F29 fault?
This fault occurs when the boiler successfully lights but cannot maintain a steady flame, causing the system to shut down for safety. The most common reasons include a blockage in the condensate drainage pipe, an unstable gas supply, or a buildup of carbon on the electrodes that monitor the flame.
This fault is significantly more common during freezing winter temperatures, as the external condensate drainage pipe can freeze and cause water to back up into the boiler.
DIY fix possible
Check that your gas emergency control valve is open and you have credit on your gas meter.Check if other gas appliances in your home, such as a hob, are working correctly.Press the reset button (indicated by a flame with a line through it) 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 F29 fault code
Click a model for the full fault code list and model-specific repair notes.
Source
Glow-worm F29 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