Hi all, I am interested in installing a DX GSHP system in my place because they are more efficient. But I have only a small garden, and I read everywhere that DX systems are mostly if not only compatible with horizontal ground loops. Do you know why that is? Why could we not have a 300ft borehole with copper tubing? Thanks, Fabien

DX can go vertical, as well as horizontal. Earthlinked designed for most heat dominated areas as, 100' vertical loops per ton, in most installation. Not sure about other DX manufactures. Over that distance ( maybe 150' ) vertical, oil return would come in play for the compressor's lubrication.

Typical configurations for DX systems (from major manufacturers - Advanced geo and Earthlinked) are 100 ft vertical, 100 ft angle drill, 70 ft vertical and 70 ft angle drill. Minor modifications can be made (40 ft per 3000 BTU/H) as well as certain horizontal configurations. As Jack notes, beyond 100 ft the oil cannot be brought back to the compressor. Without proper lubrication, the system will fail.

Paul
Total Green
www.totalgreenus.com

Water to air geo is efficient as well and can have a 300' bore in your garden.
Efficiency and size of loops in the lawn is an industry doublespeak that truely grates on me.
For instance a horizontal Earthlinked 1 ton loop is 250' of pipe and a slinky in my area is about 600' of pipe therefore Earthlinked has a smaller "footprint". However, a 6 foot per foot slinky fits into a 3' wide 110' trench while the Earthlinked calls for a 4' wide 125' trench so if we are talking impact to your lawn, water source geo has a smaller foot print.
If you talk about vertical boring a water source can have <1 bore/ton where DX has more than 1 loop/ton. So again Water source might have 300'/pipe/ton to DX's 150', but water source could put 5 tons into two boreholes where DX will have ~7. Less pipe = less footprint but does not equal less holes in your garden.
As far as efficiency, DX and water source equipment achieve some amazing numbers for peak efficiency.
If you look at average efficiency however, that's not quite the same and they all, regardless of brand or type, end up with similar averages. Operating cost differences however are seldom more than $100/yr.
If you would like to choose equipment in the way the pros and consumers here think is the best way to shop, try our "shopper's checklist" you'll notice brand and type are not among the top 5.
Good Luck,
Joe

Listen to Joe. Brand really doesn't matter as much as installer. Having been installing and promoting geo since 1995, we've seen a lot of problems arise from people mis-designing, mis-applying, skipping steps, cutting corners, etc. Have confidence in your installer, first. Anyway, check out the shopper's checklist.

Fabien,

Brand and technology is less important than the installation contractor. Way less. TuffLuck and Joe have it right. But don't forget the HVAC contractor. We've seen all kinds of systems fail because the HVAC contractor wasn't worth crap...so be sure the HVAC is part of the mix and up to speed on doing it right. The HVAC component is very important as well as the control mechanisms.

Paul
Total Green
www.TotalGreenIntl.com