Racine Wisconsin zone 5. 1400 sq ft very tight home. 8" access through foundation. 80% clay. I have a need to trench 7' ft deep in 80% clay x 700 ft long, 6" wide. Trencher will have to turn around so another trench costs little. This trench will hold 4" PVC for drainage (yes, less than 2% slope so it will be flushed) and drainpipe can saturate surrounding soil. 2.5 - 3 tons cooling should work & I believe larger than needed trenches are best. Anyone wish to offer 2 cents on a very long single loop system? DX with the 5/8" vapor in the drain trench? 3/8" liquid trench 4' away? Larger tubing? So the question is at what point is a single loop DX or liquid loop impractical? Property does not allow more than one loop but could be 1200' is available. Contractors are afraid of an out of the box design so this will be DIY. I have BS Ag Engineering, many years experience, back hoe ... and 1 year to design this.

I don't know any of the technical stuff, but 2.5 to 3 tons of cooling is a lot for a house that size. Our 1400 sq ft ICF house in SC worked out to 9K BTU, or .75 tons for cooling, and 12K BTU for heat.

What jdebree said. Even a reasonably tight code-min house in Racine would come in with a cooling load of about 1 ton, 1.5 tons if it has a lot of "sunset view" west facing windows, and a heating load of about 17,000 BTU/hr @ Racine's 99% outside design temp of of -1F. I for no good reason you followed ASHRAE's recommendation to upsize 1.4x for heating load (rather than using resistance heating strips to cover the difference when it's cooler than -1F) that would still leave you at only 24,000 BTU/hr. The smarter money would be to build better than code on U-factors, use air source heat pumps and rooftop PV to cover the difference, but if you're committed to going with ground source heat pumps instead you should be able to cut the size in half from what your'e talking.

Whether the house is already built or not, this clearly this calls for an aggressive Manual-J heat load calculation that reflects the "...very tight..." status before committing to the HVAC particulars needed to support the load. In my area (MA) it's actually cheaper up front to build the house to Net Zero Energy using rooftop PV and cold climate mini-splits than going with 1-3 tons of GSHP, but GSHP is more expensive here on average than in other local markets, thus YMMV.