I have Baxi Bermuda gas fire, with back boiler, which supplies central heating and hot water to my home. A few days ago the water heating failed. I checked the header tank which was O.K. and, on the highest thermostat setting, the central heating appeared to operate satisfactorily although, when at less than maximum setting, it failed to operate the pump. When the water heating was tested on the same maximum thermostat setting, the boiler lit for just over a minute, rested for 3 mins then reilluminated. I allowed it to operate in this way for over an hour but, although the flow and return pipes behaved as expected, the water temperature at the tap was unchanged i.e. cold. It seems that no heat exchange is taking place between the primary and secondary water supplies. I'm reasonably sure that the boiler thermostat is faulty, but that does not explain this odd behaviour. Can anyone offer any suggestions as to what I should explore next, please, or am I wandering down a blind alley? Thanks.
Tony.