Your boiler is currently working exactly as it should and is simply heating water for your taps or shower.

DHW mode: Burner on

What causes this fault?

This fault occurs when the boiler's internal flow sensor incorrectly detects that water is running through the hot water pipes, even when all your taps are closed. The most common reason is a sticking internal component or a faulty sensor that is sending a false signal to the boiler's brain. Because the boiler thinks you are prioritising a hot bath or shower, it refuses to switch over to provide heat for your radiators.