Hi, first of all, I'm an auto mechanic not an hvac guy, I should have said no when my wife's friend asked me to take a look at her boiler system. So her ex hubby replaced the thermocouple last week and ever since, one of three zones is not working. So I turned up the Tstat, separate ones for each zone, checked the pipe, hot as hell before the valve and Luke warm after. Took the cover off the power head and watched it open, took the valve itself apart and checked for movement, all good. Went up stairs bled all the radiators, got hot water out of all of them after quite a while. Still seems like no flow, hot on one side of valve and Luke warm on the other. The other 2 valves are super hot on both side.any ideas?

 

Welcome to the forums.


Are you sure ? A thermocouple is in the burner section on an older boiler.

What is the boiler pressure ?

If the cold zone is the highest one.... second floor, then possibly the boiler pressure is too low.