BoilerFaultCodesGlow-worm F24 Fault Code
The Glow-worm F24 fault code means: your boiler is heating up too quickly because water isn't flowing through the system properly, causing it to shut down to prevent overheating.. It appears on 13 Glow-worm models in our database.
Technical description: Water circulation fault (Temperature rise too fast)
What causes the Glow-worm F24 fault?
This fault occurs when the boiler detects that the internal water temperature is rising much faster than it should, triggering a safety shutdown. The most common cause is a blockage in the system or a failing pump that prevents water from moving away from the heat exchanger quickly enough. It can also be caused by air trapped in the pipework or a buildup of debris known as central heating sludge.
This fault is specifically common in autumn when homeowners turn their heating back on for the first time, as pumps can seize up after months of inactivity during the summer.
DIY fix possible
Check that your boiler pressure is between 1.0 and 1.5 bar on the digital display.Ensure all radiator valves and isolation valves under the boiler are fully open.Bleed your radiators to remove any trapped air pockets that might be blocking flow.
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Glow-worm models that show the F24 fault code
Click a model for the full fault code list and model-specific repair notes.
Source
Glow-worm F24 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 31 August 2026