Glow-worm · Energy
F.20 boiler fault code
Energy
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What F.20 means
Safety switch-off: the overheating temperature has been reached.
Safe check
Record the exact display and model from the outside label or manual. Do not open the boiler or repeatedly reset it.
When to contact an engineer
If the code appears or returns, stop using the boiler and arrange diagnosis by a Gas Safe registered engineer.
Safety notice
A boiler fault code alone is not a gas or carbon-monoxide emergency. If you smell gas, a CO alarm sounds, anyone feels unwell, or there is an unsafe flame, leave and call 0800 111 999 from outside.
Source and provenance
- Energy range fault codes
manufacturer trade support table
Checked 27 September 2026; the online page publishes no revision