BoilerFaultCodesGlow-worm F20 Fault Code
The Glow-worm F20 fault code means: your boiler's computer components are having trouble communicating with each other because they are running incompatible software versions.. It appears on 5 Glow-worm models in our database.
Technical description: Software incompatibility.
What causes the Glow-worm F20 fault?
This fault occurs when the main control board and the display panel are unable to talk to each other correctly because their internal programs do not match. This usually happens after a repair where a new part has been installed that is running a different software version than the original components. It essentially means the boiler’s 'brain' and its 'voice' are no longer speaking the same language.
Engineer required
This fault requires a Gas Safe registered engineer. Do not attempt gas-related repairs yourself.
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Glow-worm models that show the F20 fault code
Click a model for the full fault code list and model-specific repair notes.
Source
Glow-worm F20 fault code information on this page is sourced and cross-checked against the official Glow-worm service / installation manuals for each affected model.
- Glow-worm CXi manual (PDF)
- Glow-worm Easicom 24 manual (PDF)
- Glow-worm Flexicom 24c / 28c manual (PDF)
Reviewed by the BoilerFaultCodes Editorial Team · Last reviewed 7 July 2026