BoilerFaultCodesGlow-worm F.20 Fault Code
Also written as F20 — same fault.
The Glow-worm F.20 fault code means: your boiler has stopped working because it cannot correctly measure the temperature of the water flowing through it, causing the system to shut down for safety.. It appears on 18 Glow-worm models in our database.
Technical description: Flow temperature sensor (NTC) / Calibration failure
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 F.20 fault code
Click a model for the full fault code list and model-specific repair notes.
- Betacom4 Repair: £150-£300
- Compact Repair: £120-250
- Easicom3 Combi Repair: £120-250
- Easicom3 System Repair: £120-250
- Energy Repair: £150-300
- Energy Regular Repair: £150-300
- Energy System Repair: £120-250
- Energy7 Combi Repair: £150-300
- Energy7 Regular Repair: £150-300
- Energy7 System Repair: £120-250
- Essential Repair: £120-250
- Flexicom 24c / 28c Repair: £150-300
- Flexicom CXi Repair: £120-220
- MicraCom Repair: £120-250
- Sustain 12s Repair: £100-£350
- Ultimate 3 25R Repair: £120-250
- Ultimate3 Combi Repair: £120-250
- Ultimate3 System Repair: £150-300
Source
Glow-worm F.20 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 Betacom4 manual (PDF)
- Glow-worm Compact manual (PDF)
- Glow-worm Easicom3 Combi manual (PDF)
Reviewed by the BoilerFaultCodes Editorial Team · Last reviewed 7 July 2026