BoilerFaultCodesMain E20 Fault Code
The Main E20 fault code means: your boiler has lost the ability to accurately measure the temperature of the water circulating through your radiators, so it has safely shut itself down to prevent overheating.. It appears on 7 Main models in our database.
Technical description: Central Heating NTC Fault
Engineer required
This fault requires a Gas Safe registered engineer. Do not attempt gas-related repairs yourself.
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Main models that show the E20 fault code
Click a model for the full fault code list and model-specific repair notes.
Source
Main E20 fault code information on this page is sourced and cross-checked against the official Main service / installation manuals for each affected model.
Reviewed by the BoilerFaultCodes Editorial Team · Last reviewed 7 July 2026