I have a simple problem. Potterton Suprima 80 boiler. Problem since
new 1 year old. The boiler does not stay on long enough, I have temp
guage on the outlet copper pipe from boiler newer goes much above
60degree. I have had the circuit board changed, the temp sensor
changed, as recommended by various plumbers. Yet I have the same
problem. The temp control knob is on max. The same problem, the boiler
stays on for 2mins then goes off. Why does the dam thing not stay
on!!!

Anyone who has a solution, or have had similar problem most welcome to
contribute.