Went to boiler today and boiler was locking out on heating mode, after feeling around the rads some of the return pipes were cold and some rads felt slugged. Found that the flow valve was only half open and opening this fully along with all the TRVs and lock shields seemed to get the system heating again but now all the rads are scalding hot and boiler went to lock out and wouldn't reset. Going to replace high limit thermostat and check flow and return thermostats, am I doing the right thing? Any idea?
