I have a Baxi Solo 2 PF 60, for about 6 months now (on random occassions) once the heating is on it will not stop, you can turn the stat down and this makes no difference. If you turn the heating controller to off it keeps going (now the house is getting very Hot!) The only way to reset it is to turn off the permanent live feed to the boiler. I have now replaced the PCB and the central heating controller but has made no difference. Does any one have any other ideas?