Any idea why my tankless bolier makes this horrible clanking noise when used in my radiant floor system?
When I run tap water thru it (using isolator valves) everything is fine but as soon as I switch to my closed loop system it makes this noise (see video)
I have 4 loops about 200' each. Taco 10 pump with check valve, Extrol #30 tank, B&G air separator and its a very simple 1 zone system.
Im pretty sure there is no air in the system. I ran each loop for a long time until there was no bubbles. Tried different coolant pressure but I dont know what to do. Needle on the pressure gauge shakes when this noise occurs.
Willing to try any suggestions