Reply To: hot water radiant heat with hot water heater, trouble with return
mielef
Participant

I need to clarify the load. My concrete floor is a 22’x20′ slab 4″ think, which is insulated with 1.5″ blueboard. There are 3 baseboard elements, 8′ slant fin baseboards. I think the second pump should make a difference because the problem I think I have is that the water meets some resistance from air in the line. My logic is that if the water comes back warm on the first pass, it should maybe stabilize in temperature (if it’s recirculating) rather than go to very cold after a 90 minutes with the pump on. I like the analogy about the 350 chevy, I have a 427 center oiler under the hood in the garage, maybe that can be incorporated into this albatross. Does it seem plausible that air is blocking flow? I have a hosebib on the return pipe before the monoflow T on supply line back into the heater. If I run a hose out the window from the hose bib and put my thumb over the hose end, you can hear little popping sounds of air, but there has got to be a whole lot more in there! When I first filled the hot water heater tank with cold current, there was a long and continous hiss from the air float vent. I have not yet been able to purge a similar volume of air out of the loop circuits. I originally thought that the air would get forced back into the tank when I had the return reentering the heater through the bottom of the tank at the drain. Since I wasn’t convinced that the return water was getting back into the tank, I converted to the monoflow T with another expansion tank and vent on the return before the monoflow T. Still not purging the air and I believe that the single pump is not pushing all the water through. Any thoughts on whether a second pump will help maintain a fully bled supply of return water for reheating and redistributing?

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