High
E20 on Saunier Duval Thelia

Your boiler's electronic control boards are not communicating correctly, which means the system has stopped working because it cannot manage its internal settings.

Reviewed by the BoilerFaultCodes Editorial Team · Last reviewed

Call an engineer soon

Book a Gas Safe engineer within 24 to 48 hours. Your boiler may be unsafe or could break down completely if left.

Technical description

Interface PCB incompatible with main PCB

Engineer required

This is a high severity fault. Stop using the boiler and call a Gas Safe registered engineer. Do not attempt gas-related repairs yourself.

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Related fault codes

E21View →

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