Your boiler is currently running an automatic process to refill or bleed air from its internal water system, which is a normal self-maintenance routine.

Filling the product: The diverter valve moves to the mid-position. The burner and pumps switch off (to fill or drain the product). If the pressure is lower than 0.03 MPa (0.3 bar) and then is above 0.05 MPa (0.5 bar) for longer than 15 seconds, the automatic purging function is activated. The function is active for 15 minutes.