I am running my boiler temp at 120. My return temperature is roughly 85. With a 4.2 gpm. I have 11 different loops little over 3000 feet of 1/2 tubing in 6" concrete.
Did you happen to figure out your temp issue regarding the 6 degree difference? If so, what was the problem? I have spoken with Hydro-smart and haven't got anywhere with them. They keep on telling me to play with the thermostate. I have mine set on 70. It will drop to 66. Then it takes 10 hours...