High Lockout
F 0A on Ideal Logic Max Combi

Your boiler has detected that the water is flowing in the wrong direction through the pipes or that the temperature sensors have been installed on the wrong pipes.

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

Flow/Return Reversed

What causes this fault?

This fault occurs when the boiler detects that heat is rising on the return pipe faster than the flow pipe, suggesting the water is moving backwards. It is often caused by a failing internal pump that can no longer push water in the right direction or faulty sensors that are sending incorrect temperature readings to the control board.

This issue often surfaces when the heating is first turned on in autumn, as pumps can seize or become sluggish after being inactive throughout the summer.

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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