I have a Ferroli Optimax HE 31S boiler if I turn it off and on at the wall it will work fine for say 8 hours. If the timer turns off over night then in the morning the system detects that heat is required, the pump starts, the fan starts but there is no flame. The system just pumps the cool water around the system. There is no fault code. If I then turn it off and on at the wall it seems to work fine.