No problem with the hot water but after a few minutes of ch running, the overheat stat cuts out. In the short time it is on, the first radiator gets very hot at the top only and the other radiators are barely aired. A local tradesman replaced the overheat stat, control stat,flue stat and sequence board. It still didn't work and he ran for cover never to be seen again. Since most of the main condensing boiler components seem to have been replaced does anyone have any ideas?