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.

Flow return reversed

What causes this fault?

This fault occurs when the boiler detects that the return pipe is hotter than the flow pipe, suggesting the water is moving backwards through the unit. It is often caused by a failing internal pump that cannot push water in the right direction, or by the temperature sensors becoming faulty and sending incorrect readings to the control board.