My central heating system is causing misery. My potterson boiler, keep going into lockout mode, My water is very hot, but before my rads reach the temperture set by the room thermo, the boiler goes into lockout mode. I have also noticed that the downstairs rads, are cooler than up stairs (although all rads are cooler at the bottoms) I did have this same problem intermittently through the summer when only hot water in use, if i didnt draw the water off the boiler went into LOCKOUT Mode. PLEASE ADVISE ...