Has anyone a view on the life cycle of these valves? My boiler was replaced 10 years ago, the installer fitting 2 of these valves next to the pump in the airing cupboard, he also fitted TRV's to the rads removing the room stat. I am now in the process of replacing a ZA5 for the third time, the first failed after 7 years, the second after 9 years, both requiring a partial drain down, the C/H one has now failed again after only 3.5 years. All failures exhibit the same symptoms, valve shuts down after signal from programmer, microswitch stays in open circuit and pump and boiler continue, pumping continuously through relief pipe. Am I best to just replace the microswitch or could it be something else in the valve?
