First ground loop

Since my friend Matt gave me lots of 3/4" PEX for this project, I'm going to see if I can get away with using it for the ground loops. Its walls are pretty thick and PEX is a pretty good insulator, so I'm not sure it's that great of a choice for the ground loop. Copper would be nice, but unless I can get a really good deal on some surplus K-type copper pipe, the cost will be prohibitive.

The first well (borehole) will be 6 feet deep and will contain two PEX loops, for a total of about 24 feet of buried pipe. Geothermal systems don't usually use multiple loops per well, but with such shallow holes and with the small temperature differentials that we'll have (since we're not using a heat pump), we'll need the water to be exposed to the ground longer than in a normal system. Multiple passes through each well will help the water get closer to the soil temperature.

I formed U-bends with PolyAlloy elbows. It's unfortunate that I have to use crimp fittings at the bottom of these loops, but I just can't figure out any better way to form a U-bend that will fit in my 5-inch diameter holes. I tried heating and bending the PEX into a 180-degree U with a heat gun, but I just made a mess.

The PEX has an arc to it because it comes on a roll. I had a tough time getting it to straighten out, so I ended up strapping the pieces to a long piece of wood for support. I realize that this will rot over the years and cause a little sink hole, but I'm not too worried about that.

In this picture you can see the "Tee" fittings that contain the mid-loop temperature sensors, as well as a temperature sensor attached to the bottom to measure soil temperature at 6 feet. There are similar sensors attached at 3 feet and near the surface. Click for a full-size image.



Here is the ground loop ready to bury:



Here is the ground loop inserted into the ground: