Geothermal Heat Pump Project

[techman]

Start of the trench. As you can see the ground is mostly shale with a little dirt mixed in.

paul

 

[techman]

Here is the trench progressing. I had planned for a 7' deep trench, but at an average of 6.5' we hit blue shale (solid layer of hard shale), so we stopped when we hit that layer. In actuality the solid layer has a better heat conductivity than the surrounding soil.

paul

 

[techman]

As Bob was digging, I made up the first header and coupled one end of each coil to the header. The line ran vertical to an elbow and a straight run to the house.

paul

 

[techman]

Here is what the yard was starting to look like. The average height of the piles was about 5'

paul

 

[techman]

Another view of the yard. here you can see the "bridge" area to get to the center of the island. The tubing is mostly still in the coils as seen here. The coils were quite heavy and handling was sometimes an issue.

paul

 

[techman]

Here is a shot of the tubes in the bottom of the trench. One difficulty was that the coils had to be "unwound" without twisting. The tubing is quite stiff and will not lay flat if there are any lengthwise twists in the line. Often I had to flip the coils to take the twist out so it would lay flat.

paul

 

[techman]

The tubing needs to have good thermal coupling to the ground, so the entire length, at both layers has gravel screenings put in to surround the tubing. Approximately 6" minimum around the tubing is needed. Screenings are very fine, almost like sand, and fill all of the voids between the soil, rocks and the tubing. It is a critical component for good performance. I used nearly 60 tons of screenings on the job.

paul

 

[techman]

Here is a design cross section of how the tubes are installed

paul

 

[ESM]

Paul,

All the info is great! Thank you for putting the time into sharing your experience. I've learned a lot since we started discussing this back under the Kubota owners forum. For others who may be interested in tackling an installation themselves, the International Ground Source Heat Pump Association (http://www.igshpa.okstate.edu) offers Accredited Installer Workshops. I'm hoping to go through the course in May, in fact, it's up in your area of the country, Bethlehem PA. It's also offered in a few other states and Canada. I'm looking forward to reading more about your project.

Eric

 

[techman]

Here is a view of just a portion of the total screenings I put in.

paul