High
E78 on Alpha Intec 50CS

Your boiler is struggling because the water inside is not circulating properly, causing a significant temperature difference between the water leaving and returning to the unit.

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

High flow/return temperature differential

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

E04View →E06View →

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