Ground source heat & air?

[Larry2]

If one wanted to contruct a ground source system of five tons capacity, how large would the field need to be? I'm talking about using a horizontal array of piping, burried 5-1/2 to 6 foot deep. I'm thinking a backhoe operator could knock out trenching a field in a day; the task would be quite similar to construction of a septic tank field. A backhoe would cost maybe $60-$70 per hour.

I read of grouting vertical systems to improve heat transfer. Would one also grout an array of buried pipe for the same reason?

What does the pipe, fittings, equipment and that sort of thing cost? I'm thinking the high prices I see for these systems are because of limited relection of contractors. Maybe it's wishful thinking on my part.

[NoNickName]

It depends on the type of soil. Normal moist soil is capable of releasing 20Watts per linear meter of pipe at 1.8 meters in the underground and pipes 0.7 meters apart, but for a maximum extraction of 1800 kWh/year for heating only and 2400 kWh/year for heating and cooling.

Boreholes ground heat collectors can release 50-100Watts per meter per borehole.

Costs are approx 1000-1500 euro per 200mm diam. drilling, including grouting with bentonite. Costs may increase in case of sand or stone soil.

[Peter_1]

I have some books of the IGSHPA.
Where are you living in the US?
For a common house, making the trenches can be done in 1 day.
Some rules if installed horizontally, take 5 to 7 times the surface of the house.
+/- 2kW for a verticla borehole.
Horizontal trenches are normally backfilled with the ground taken out the trench. No additional thermal enhanced grouting.
Slinky loop is also possible.
You can use normal PE3408 Pipe and weld it yuourself with a mirror welder (don't know the correct English expression for it)
Don't make the pipe runs too long.
Parallel systems, use one loop for each ton of heat pump capacity.
You can install more then one pipe in a trench.

[Abby Normal]

It depends on where you are as to how much pipe, how long the trenches are but don't waste your time with a mickey mouse backhoe. A machine that costs twice as much will dig 4 times as fast.

[Larry2]

Thanks everyone. It seems the trench system required would be more extensive than I first thought. I found some data for the States at http://www.geokiss.com/ and it would cost more installation price than I imagined.