Thanks for all the information, looks like I have missed a few steps in my system design. What will happen to my concrete with current setup?
First off, running high temp water throws a HUGE amount of heat into the concrete, which we know is a very big heat sink. A wall thermostat, which most folks use, will satisfy when the air temp reaches the setpoint. When that happens however, the slab is usually too hot to stand on which in turn continues to radiate heat into the room well after the pump stops, and overshoots the setpoint. Let's say setpoint is 70, but the air temp gets up to 75 because the slab is so hot. After this, it may take 18 hours to get the air temp back down to 68 or wherever the stat kicks the pump back on- at that point, the slab is cold again and you start all over. You want the water to be the bare minimum temperature. If it circulated constantly but maintained air temp would actually be the most efficient system possible, which is almost achievable with the use of outdoor reset. A typical floor runs 90-110 degree water depending on load and desired air temp. This keeps a more constant slab temp which keeps a more constant air temp. Also, the constant hot/cold cycles of running high temp water destroys concrete and cracks the piss out of it.