Hello all,

After reading through many threads here on this subject I am still uncertain whether a open loop SCW with a seperate return well is viable for this scenaro:

Location is SW Montana; estimated 4 to 5 tons required (sorry, no precise heat calc performed yet for a well-insulated house).  Proposed GSHP system type; WaterFurnace Synergy 3D or rough equal for radiant floor (gypcrete thin-slab), forced air AC (electric strip backup), & desuperheater.  

There is plenty of flat land to work with so any system type could be installed.  My biggest horizontal closed-loop concern: very soft, powdery loamy+fine sandy soil (no rocks at all a good thing), soil may have low conductivity issues and is still very dry at 5' down (only 10" annual precip). 

A domestic water well will need to be punched and may be upsized for light irrigation purposes and yield boost.  Adjacent properties have both residential and some irrigation wells averaging 250' to 275' deep with standing water to 100' of surface.  Yields are almost always high: between 25 to 35+ gpm.  Precise water quality is unknown but adjacents don't have or need water softening systems (anedotal evidence only, no test data available yet).  Bedrock depth is usually between 50 to 120'.  Groundwater temp in the area is reported at 55 to 56 degrees.

This is new construction and I am weighing all pros/cons/costs.  Although there are virtually no regulations in this area, alternates such a surface discharge system are personally undesirable.  Also, I don't think a single standing column system (at these depths) with either a closed or open return loop will support the tonnage adequately.

The cost of the second well is mostly offset by not having to buy and bury a couple of 1000 gallon propane tanks so it would come down to the Geo equipment upgrade costs versus conventional high-eff. propane equipment.  For cost estimating I'm also guessing the return well would be drilled down to the same depth and aquafer as the supply well.

One of my thoughts was that if this scenario is viable why not have a seperate pipe in the supply well feeding a small low-pressure jet-pump for the heat-pump unit with a return pipe sending water back down to near the bottom of the second well?  Shouldn't that significantly reduce the pumping power needed since both intake and discharge would be at roughly the same elevation (standing water) and I'm also not pumping Geo water up to domestic water supply pressures?  Maybe adding a check valve to the supply pipe inlet near the bottom of the well and adding a fill valve inside the house to prime the supply-side pipe would make a much smaller pump possible?

Any and all constructive thoughts are appricated.

Thump

Just some general speculation about this:

A four ton unit would probably need 2 wells at 300 feet each to meet your needs.  So drilling two wells for an open source would not save much money (albeit an open source is slightly more efficient).

If you drill one well slightly larger than you need for drinking water then you probably could put one set of pipes down that well.  This would make it effectively a standing well and the other would be just a regular well.

Since you have plenty of land you could always add some horizonal loop too.

I would try to super insulate and avoid the need for a five ton unit.  This saves by letting you get a smaller unit and smaller well field plus you need less energy all the time.

Again, this are just some thoughts - without more information this is just speculation.