I found my Geothermal heat source!
It's been right under my nose since 1973 (well, about 12 feet under my nose). The basement floor!
We have a zone of forced hotwater heat down there, but right after
you turn off the heat, that full basement slab and 8" walls swing
the air temp right back towards ground water temp..
Since this heat is coming from solar warming the earth's outer crust , my guess is by the end of winter, we might see down to around 57 or so.
My point?
I don't need no stinking pipes buried in the back yard. I've got my basement full of 64 degree air(72 today)..
If cold air is injected into the basement, the slab warms it back up pretty quick.
Now, I'm looking at the possibility of installing a large window type AC unit
down in the basement and venting the "waste" air upstairs for space heating.
This is the AC I've been thinking of..
http//210.118.57.197/Products/AirConditioner/ElectronicControl/AW25ECB7XAA.asp
It would cool the basement, (while heating upstairs), hitting us with 25,000 BTU/h (Unless we used low speed).
Power source: 208-230 V
Power input: 2,600/2,660 watts
Power amperage: 12.8/12.0
It takes about 7,268 Watts/h to generate 25,000 BTU/h if you use resistive heating elements (common electric space heaters) .
Since the Samsung will be a little loud, I would use it during the day and go to oil heat at night. Adding a thermostat to control it will be simple. (attaching a small warming resistor to the AC's air temp sensor).
The basement will get cold, but will come back to normal overnight.
Since the boiler will be hot 24/7 any waste heat from it will be scavenged
but the Samsung AC (aka Heatpump).