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Will a Danfoss ESBE VTC thermic valve used to control return temp lock up the system flow?
I have had an ESBE VTC sitting on my shelf for at least a year because I'm not sure it will do what I need. Since I am replacing the boiler in the next few months I have it penciled in to the new design. Before I go ahead I hope someone with experience can explain its operation - maybe I'm just reading the literature wrong. Here is my concern - if I have this sitting on the return side with a 122F element installed, it seems on the surface (and from the docs) that it will be open as long as the return water is >= 122F. It opens slowly across a 18F range so at 140F is fully open. When it's not open it will be in bypass where the system return water is blocked and it bypasses the supply back to the boiler return (is this correct? wouldn't this cause short cycling?) I just don't understand is how this valve works in a real-life system. I have 6 zones - all finned BB. If one gets turned on that's been off for a while, the return water can be, let's say 100F. So if that's the only zone open for some reason, how does the valve ever open? It will stay in bypass until warmer water arrives, but the warmer water can't get there because it's blocked by the cold water ahead of in the return line. It's like a lock up. What am I missing?