I tried repiping the chiller to a primary/secondary delivery system. The Taco 11 pump was set up to pump through the primary loop and feed into and out of the secondary loop powered by the Grundfos variable speed pump. I put in closely spaced tees and sent the water into the “hot” supply side of the radiant system where it is pumped through the open valves into the cold return system and back into the chiller.
The front of the chiller is the input from the return side of the radiant system. The return pipe connects to the primary loop through the closely spaced tees then through the chiller to the output water from the back of the chiller through the pump and then to the tee that feeds the supply side of the radiant system.
Unfortunately, the new system’s return water was even hotter than without the primary secondary piping. The controller read about 74 degrees and running the chiller all night did not reduce the temperature of the input water from the radiant system. In theory this return water would continue to get cooler and eventually cool enough to shut off the chiller. Running the chiller also added heat to the room so the morning temperature was over 80 degrees inside with 66 degrees outside.
This lack of chilling of the water in the pipes makes no sense to me. I figure each 106 ft. of 1/2 inch pex holds a gallon of water. There are about 1470 ft. of pipe in the floor and maybe 80 more ft above the floor. Some of that is 3/4″ or 1 1/4″. So approximately 14-15 gallons in the floor and 80 ft. of 3/4″ pipe would add about 2 gallons to the total.
The chiller is rated to cool 300 gallons of water at 12-22 gph. Of course it is adding heat to the air around the tank but it seems that it should be chilling the water going through it anyway. When the pipes to the floor are shut off, the chiller comes on correctly and shuts off when the water cools enough. But I can’t get the radiant system water to cool so that the concrete floor can be chilled.
I hope I can eventually figure this out.