BoilerFaultCodesWhat the manual says
Manufacturer manualFlow/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.
Avoid the next call-out bill
A cover plan would handle faults like F 0A: no call-out fees, no surprise bills.
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