Any body install a Geo-Thermal field?

[Paddy]

Trying to make good use of one's own tractor. ie justify buying one that is!.

Appears to be several approches.

Narrow trench, one pipe
Wider, several pipes
3'+, coil or Slinky

Any experince?

 

[studuster]

10 years ago when we built our house we installed a geo-thermal system for both heat and cooling. We have a 4800 sq ft home and used about 8,000'+ of cross linked poly pipe buried 5' in 8 trenches which were about 300 ' long. Our soil is sand and I attempted to dig the trenches with a backhoe but could not keep the sides from caving in so resorted to a trakscavator with a 24" hoe. At the end of each trench we dug a 6' diameter hole so the pipe could loop back. We filled the loop system with 20 gallons of RV antifreeze mixed with water. The system works very well and we have had no problems whatsoever. Highest ever electrical bill for a 2 month period was $175.00. House is 100% electrical. We live in an area where we experience 4 distinct seasons. Summers are occasionally over 100 and each winter we have several days below zero with 3 to 4 months of continous snow cover.

 

[ns_in_tex]

Do you know your average cost per KWH?

What do you estimate the payback time period?

Sounds like a good system.

 

[Paddy]

Did you fuse the pipe yourself? I've read on Geo sites this is done with 500 deg F heat.
http://www.justgeothermal.com/geoeconomics.html

I have taken intrest in installing my own field because I feel I can do it myself. The field is quite expensive.

I live in Southern Indiana and we have both cold and hot
seasons too.

I kind of like the slinky method. That is where the pipe coil is layed flat. Then each layer is slid 10 to 20" down the trench. The use of the pipe is not as efficient as straight but you can imagine how much more you lay for a given trench.

 

[Paddy]

If you are heating with Ele now, not as long as you might think. With natural gas, quite a bit longer. Cruise the Geo-Thermal sites. There's a ton, pun intended, of imfo on Geo systems.

 

[studuster]

I am located in the Northern section of Eastern Washington and our residential KWA rate is $.044 which is fairly low due to our hydro dams.
My HVAC guy fused the pipe with a special heating/clamp unit. The pipe is coiled in the trenches. The system was only about $3,000 more than a conventional heat pump unit and he said we would get twice the life over a conventional system. I have no idea what the payback is over a conventional heat pump system but might guess 4 to 5 years?? One big difference is that the air coming from the registers is not as warm as from a conventional heat pump unit. The system does have auxillary heating strips when it really gets cold out but mine doesn't come on unless we crank up the thermostat for a quick warm up. We were told to not install those set back type thermostats as it is much more efficient for a geo thermal system to maintain a constant temp rather than cycle up and down. I would not hesitate to install another.

 

[Rch]

In our area of central WI with clay base they go 8-9 ft deep. They place a 3" perforated black plastic drainage pipe about a foot or two above the tubing and run water in several times the first 2 summers to facilitate the trench "caving in" and making intimate contact with the soil for better heat/cool transfer. Therefore route trenches accordingly. One guys electrical went irratic 2 years out from the underground electrical service literally being pulled out of his breaker panel from the settling of the trenches pulling on the underground line /forums/images/graemlins/shocked.gif

 

[Westonium]

I am extremely interested in this as well. I know that cross-linked poly (I think its called PEX)is cheap, but I am really leaning towards a copper solution - it conducts heat waay better than PEX. It may cost 3 times as much, but it conducts heat thousands of times better than PEX.

I've had people try to scare me off of Geo with claims of "IT WILL CAUSE PERMA FROST" which is ridiculous. If you buried it shallow, and not enough of whatever pipe - yeah I could see it. I don't think square footage of field is my limiting factor, but for some people it might be. For those people they go vertically.

There is nothing about Geo that means it should pump less heat - that work is done by the compressor. The only difference between Geo and traditional is one uses an air heat exchange (sometimes noisy) vs. ground.

The Geo system just makes more sense. Which to pump heat out of in winter...lessee um 20 degree air or 60 ish degree ground. Tough call. Which to dump heat into - heat soaked 90-100 degree air or 60ish degree ground (based on how cold our well water is in summer I'm wagering on ground).

I can't believe every house in the US isn't going Geo. I'm doing it next summer. I just moved in and have already spent way more than we budgeted to fix this place up and our son is due to arrive in a month+ 15 days. This winter though, I PLAN.

PS. I'll be sure to photo the whole thing when I do.

 

[Paddy]

Cu tubing has it's advantages as noted. Typically when Cu is used, freon is the liquid. This eliminates one of the transfer links. Cu has corosion issues though. I also understand there is only one manufacture that uses direct Cu/freon field. Leakage can be an expensive fix. I have read that the Cu field is much smaller.

As you stated, perma-frost and a heat saturated field is
prevented by adiquate field size.

A tempting method is the 'two well' system 50' apart. My home site is located on a large lake and I would like to have wells as near as leagaly can be. Well water can deposite minerals that have to be flushed/disolved ever so often.

Either method has to be beter than burning fuel in side your home.

 

[slowrev]

Just one comment. In the air transfer heat pumps the compressor is outside. with the geothermal heatpumps the compressor is usually inside which makes it noisier inside the house than the air tranfer pumps.

Ben