I have one concern with your plan. With the temps in your area and the insulation levels you have on the wall and attic I believe you will be over capacity. Here is my reasoning. Here in Michigan we sometimes have winter temps as low as -15°F. I have a 3.5 ton single stage open loop system that will hold the house at 70°F without any other auxiliary heat down to 11°F outside temp. My system reaches 100% duty cycle around 14°F outside temp. My walls are r20 and r40 attic, and I'm heating 2270 sq ft. main and second level plus 1450 in my basement.

Comparing to my temps, square footage and insulation to your area and home, I believe two 2 ton units will be overkill. Most contractors will size the system to be over capacity to insure the homeowner doesn't complain that the system “runs too much” or “doesn't heat fast enough”. Your home seems to be designed around efficiency. If this is the theme then you may want to look at smaller units that run more frequent. Some of the other advantages of a system that runs more is better air quality and more even temperatures throughout the house.

Your choice of Water Furnace would be fine. I prefer the Copeland scroll compressors which your Water Furnace should have. On your ductwork, you mentioned that it is insulated. Is it internally insulated? If not, be sure to have the inlet and outlet internally insulated for noise control.

Your project sounds like a fun one and I see no reason that you couldn't complete the installation yourself. The problem you will run into on a do it yourself install, is getting the hardware and information. Warranty could be an issue as well. If you really wish to complete the system yourself and knowing the issues of roadblocks mentioned above, I believe you can find ways to deal with them to allow you to do what you want.

I wish you the best with your new geosystem and at sometime I would really like to hear more about your 6.4kW solar system. If you can put something like that together, the geosystem should be a piece of cake!

Regards,

Eric D

Thanks very much for the replies!!  The advice about looking at smaller systems is very helpful - and that would likely make the install easier and less expensive.

Regarding finding someone out here who can help with this, it seems to be a little more difficult than in other parts of the country.  Around here, regular heat pump systems are rare enough - when you start talking geothermal, installer's eyes just glaze over.  Most everyone in this area lives on postage-stamp sized lots, so there's not much room to put a ground-loop system.  And, there are big restrictions against drilling wells - so getting a licensed driller to put a vertical system in place is going to cost BIG $$$ and BIG paperwork with the County/State.  So, the market for these systems hasn't materialized.  I'm lucky in that I live way out in the middle of 'nowhere' - a very rural area where you wouldn't believe that Silicon Valley is just over the hill.  That comes with its problems, though - we barely have electrical service, no gas service, no water service, and no sewer.  So, folks out here have to be pretty self-sufficient.

The solar system I put together is pretty cool - it consists of 6.4kW of panels mounted on a south-facing hillside about 500 feet from my house.  I had to get my backhoe down a VERY steep hillside to dig the 7' deep holes for the four pole-mounted arrays, and then mix and pour 8 yards of concrete for the footings by hand (that was a pain).  Then, trenching 500' back to the house and laying four strands of 4-0 underground service cable was a bit of a challenge.  In the power shed, I have four Outback GVFX3648 inverters (14.4kW of continuous capacity), and I'm using a 48V Solar-One battery bank that has 1690 A-h of capacity (enough to keep the whole property going for a week with minimal sun).  To all of that, I added a 1kW hydroelectric generator that runs continuously during the times of year when the trout spawning is over and the eggs have hatched.  All in all, the county inspectors were pretty blown away with the system - they'd never seen anything quite so complex, yet so cleanly installed.  Best of all, I saved about $50K by doing all the work myself.   Next to the backhoe, the solar system has been the best investmetn I've ever made.  Power goes out all the time here in the winter, and sometimes for days at a time.  The switchover from grid to backup power happens so fast that I don't even notice it - it's not until neighbors start coming over to hang out that I realize we've all lost regular electricity.

Just playing with some numbers, if the well is 6 x 6 x 35 and full of 60°F water, and if you used it down to 35°F, with no change over of the water, and if you had a heat loss of about 20000 btuh, the well could provide heating for about 4 days.  To calculate if there would be enough capacity for heating for an extended number of days you would need to do a flow test to find what amount of water could be drawn from the well for an extended period of time.  Just dropping a slinky coil would not tell you if there is enough capacity.  

Thanks guys - great information here!  I have a feeling this is going to turn into one of the forums that I spend a lot of time on. 

The wells are around 100' from each side of the house, so at the very least I'd have to trench that much.  Being an engineer, I'm prone to designing for worst case scenario, so my thoughts are to do a 'minimum recommended' size trench with slinky coils, and then use the wells as bonus heat sources at the far end of each trench.  Since we've had some very weird weather phenomena during the past few years, I'm not going to bet much on the wells being completely full when I need them, but they might help make this system a bit more efficient.