2 pipes in 1 vertical borehole?

[knothandy]

I was just told that I could improve my thermal performance by dropping two loops into each vertical borehole (I just drilled 2 X 250 ft. holes). Obviously that would double my capacity but has anyone every heard of doing this? What are the downsides? The pipes would be right next to each other in the same hole. Is there any reason NOT to do this? Is it a waste of pipe? More work on the pumps (ie. substantially more work)?

[Speedwrench]

IGSHPA - Down to Earth Energy
supposed to be the authority for info.

life begins when the kids leave home and the dog dies

[knothandy]

IGSHPA says that they DO NOT offer technical advice, consulting or opinions on GSHP installations. If help or advice is needed with an installation they recommend contacting an Accredited Installer or Certified GeoExchange Designer.

I did get feedback from another site:
- 2 loops in 1 borehole is an accepted but seldom used practice
- It offers about 10 -20 % more effective heat exchange
- Getting two loops down the same hole might be difficult
- This source stated that they had installed thousands of loops in boreholes but never put two in the same hole.
- If I really want to do it, there is no good reason not to but there just isn't a good reason to do it either.

Thanks for any additional advice. I'm also going to ask the guys running the drilling rig if they will find it difficult to do cleanly.