Ladia,
That explains why your system is more complicated than mine. Again, mine is strictly forced air heat & cool, with the super deheater heating the hot water. I have pex tubing in the entire basement floor, in 6" of suspended concrete in the kitchen, and 3" suspended concrete in the master bath, but none of it is hooked up yet. I have not figured an easy way to use the geo system to warm these floors, since I am pretty much using all of the hot water the system produces for domestic. In fact, my electric bill stayed the same last fall when we quit using the A/C. The electric water heater had to take over. I might as well keep running the A/C.
I am thinking of just using a small water heater and pump to circulate 90 - 100 degree water through these floors. It won't be so much to heat the house, just enough to take the chill off the tile floors.
As you mentioned earlier, with radiant heat, especially in concrete, you can't just decide to raise the temperature because you are chilly. It takes several hours to make an adjustment, both up and down. Does your system look at the temperature and trend outside to decide that it's time to start (or stop) warming the floors? I don't know if I will need this or not, but it is something I would like to learn more about.
Seems to me that I got myself deep in the discussion about geothermal heating cooling so I should make one thing clear. I am not an expert on geothermal heating but I learned a lot while implementing geo in my own house. My intention is to share my own experience with my own geo system to help other people to avoid mistakes I made and/or help them to be better informed about the issues associated with the geothermal systems. My background is in control systems. I install and set up control systems for industrial processes (such as oil refineries and chemical plants) for living. Therefore I decided to design and make my own control box because of the shelf product was not available at that time. It was also fun project but if you ask me if I would do it again the answer is NO. I would do it again only if there isn’t an alternative.
My system is complex (not necessarily complicated) due to the fact that I have several zones each with individual temperature control. I have integrated whole house filter with the AC. The filter uses the same ducts but otherwise it is separate unit with its own fan and heat recovery etc.
Both the heat accumulator as well as HW heater have individual temperature control. I might add AC with all associated temperature and occupancy control for the garage/shop later on.
Switching from heating to AC is automatic. We have one "smart" thermostat (located in the kitchen) that has built in an algorithm to select heating and cooling mode but I found that it could get “fooled” in example by baking Christmas cookies that generates a lot of heat or when we used a fireplace etc. Therefore I added a logic that checks if the demand for heating or cooling is sustained and then switch. The heat accumulator is "charged" (kept hot or cold) only if there is a demand for heating or cooling. The original control system kept the accumulator charged even when there wasn't demand for heating or cooling for several weeks at spring or fall. All pumps are cycled every day for one minute to prevent sticking due to long inactivity etc. The control box also controls the cycle for HW recirculator so there virtually instant hot water from the faucets but the recirculator doesn’t need to run continuously.
The temperature in the heat accumulator is fixed so the system doesn't look at ambient temperature but I might add the sensor just for information.
I wouldn’t use direct heat for floor unless you can’t justify the cost of adding the floor heating to the HP. The HP will heat the floor four times cheaper at retail electricity cost and about 8 times cheaper at wholesale cost. The cost and complication will depend on your system. I don’t know if your system has separate fan coil or if it is all in single unit similar to furnace. It might or might not have heat accumulator and/or even provision for floor heating hookup (in ex: built in heat exchanger and circulation pump). One thing you need to know about floor heating is that the floor is cold to touch. It feels warm only if you have socks or shoes.
