High
B 30 on Keston C90 / C110

Your boiler is struggling to pump water around your heating system effectively, meaning it cannot move the hot water away from its internal components quickly enough.

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

Difference between flow and return temperatures too high. Check water circulation

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

B 29View →

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