Geothermal Heat Pump Project

techman · Mar 5, 2006

Line damage, while possible I think is unlikely. The wall of the tube is quite thick. Also having a 6"+ layer of screenings keeps the rocks from directly contacting the tubing. Also since the tubing is below the frost line, little movement would be expected in the surrounding soil.

paul

18KwPower · Jun 1, 2006

( Chapter 2
--[snipped]--
- Vertical loop: This uses vertical bore holes 200'-500' deep with a loop of tubing in the hole. Costly drilling is required and the hole with tubing needs to be grouted solid, from the bottom up, to thermally "couple" the tubing to the surrounding earth. The number of holes is determined by the unit sizing and other ground factors. A local firm would do the entire loop system, grouted and finished for $ 2K to $ 10K depending on the sizing, etc. This is an ideal choice for small lots, but since I have 11+ acres, it did not make sense for me.

- Horizontal loops: This like the vertical is a closed loop system (circulate water through a closed pipe loop) but uses pipes buried in a trench.
--[snipped]--
paul
)

Having had a Heat Pump since 1992, I thought a few comments about my system would be appropriate.

1. I have a vertical loop. Cost to install was $2500 in 1992. It consists of four 110' wells (3tons). Yes the pipe is grouted in. 100% efficiency the first year and thereafter... Minimal destruction to the yard. Second year, nobody could tell where the loop was.

Note: current drilling prices are about .75 to $1 a foot. Depth of the wells is dependent on where they hit limestone/bedrock.

2. Horizontal loops. They take several years to reach peak performance. Because the soil need to compact around the tubing... Note that for the vertical well they grout the tubing in. So, almost everyone I know with a horizontal loop also has a soaker line on top of the horizontal loop.

The new way to do horizontal loops is to dig a big hole, then they use a horizontal boring machine to do the hole. Yes, this is the same type of machine that they drill under roads etc to put in phone/service lines in many areas. I haven't actually seen this done yet. But a friend of mine is getting this kind of ground loop... So I will soon know more.

Heating costs per month in Iowa were $40 -- $55 for 2-1/2 ton unit on a 3200 sq ft house. 600 sq ft has radiant heat.

-Dave

18KwPower · Jun 1, 2006

( Chapter 2
--[snipped]--
- Vertical loop: This uses vertical bore holes 200'-500' deep with a loop of tubing in the hole. Costly drilling is required and the hole with tubing needs to be grouted solid, from the bottom up, to thermally "couple" the tubing to the surrounding earth. The number of holes is determined by the unit sizing and other ground factors. A local firm would do the entire loop system, grouted and finished for $ 2K to $ 10K depending on the sizing, etc. This is an ideal choice for small lots, but since I have 11+ acres, it did not make sense for me.

- Horizontal loops: This like the vertical is a closed loop system (circulate water through a closed pipe loop) but uses pipes buried in a trench.
--[snipped]--
paul
)

Having had a Heat Pump since 1992, I thought a few comments about my system would be appropriate.

1. I have a vertical loop. Cost to install was $2500 in 1992. It consists of four 110' wells (3tons). Yes the pipe is grouted in. 100% efficiency the first year and thereafter... Minimal destruction to the yard. Second year, nobody could tell where the loop was.

Note: current drilling prices are about .75 to $1 a foot. Depth of the wells is dependent on where they hit limestone/bedrock.

2. Horizontal loops. They take several years to reach peak performance. Because the soil need to compact around the tubing... Note that for the vertical well they grout the tubing in. So, almost everyone I know with a horizontal loop also has a soaker line on top of the horizontal loop.

The new way to do horizontal loops is to dig a big hole, then they use a horizontal boring machine to do the hole. Yes, this is the same type of machine that they drill under roads etc to put in phone/service lines in many areas. I haven't actually seen this done yet. But a friend of mine is getting this kind of ground loop... So I will soon know more.

Heating costs per month in Iowa were $40 -- $55 for 2-1/2 ton unit on a 3200 sq ft house. 600 sq ft has radiant heat.

-Dave

techman · Jun 2, 2006

Just a quick update. Since the system was installed last fall, it was not until now that the air conditioning capability was run.

Performance in the winter was great and likewise cooling is also working very well. I checked the power draw in cooling mode this week: the 2 ton unit (24,000 BTU) is drawing about 1 KW, which is less that the average small window unit. Considering that the incoming loop water temperature is 59 deg., and the evap temp is nominally between 50 and 55 deg, the compressor does very little work beyond just pumping the freon.

Paul

techman · Jun 2, 2006

Just a quick update. Since the system was installed last fall, it was not until now that the air conditioning capability was run.

Performance in the winter was great and likewise cooling is also working very well. I checked the power draw in cooling mode this week: the 2 ton unit (24,000 BTU) is drawing about 1 KW, which is less that the average small window unit. Considering that the incoming loop water temperature is 59 deg., and the evap temp is nominally between 50 and 55 deg, the compressor does very little work beyond just pumping the freon.

Paul

Highbeam · Jun 2, 2006

So just moving coolant through the ground would cool it enough to have a cold radiator. That's something I hadn't considered, you could just bury a long hose with a circulator and run the liquid through an old fashioned radiator with ground temps that cool.

Highbeam · Jun 2, 2006

So just moving coolant through the ground would cool it enough to have a cold radiator. That's something I hadn't considered, you could just bury a long hose with a circulator and run the liquid through an old fashioned radiator with ground temps that cool.

czechsonofagun · Feb 7, 2007

Great information. I am lucky enough to have a pond 200 feet from the house, geothermal unit makes the most sense as a heat source for us and one day I will make it happen.

dirtworksequip · Feb 8, 2007

I didn't have time to read thru all your post,but will when I have more time. I did view a couple of pics of your system. In the one pic you showed the tubing in the ditch. It would concern me that there was so much rock and shale in contact with the tubing. Over time the vibration of pushing a liquid thru the pipe will wear a hole in the tubing. I also noticed that you did your manifold outside under ground. What happens if you develope a leak in one of the runs in the dead of winter? Wouldn't it have been better to had the manifold inside your basement with values on each run so that if you did develope a leak you could isolate that run and still run the remaining system runs?

techman · Feb 8, 2007

The picture of the tubing was not a finished shot. About of 1 foot of screenings were put in and the tubing was lifted and centered in the screenings, so there is no shale in direct contact with the tubing. Also the tubing is 200 PSI rated with nearly 1/4" wall, tough to cut through even with a sharp knife. I feel very comfortable with the screenings protecting the tubing, and also providing a thermal coupling.

As far as the manifolds, the joints are thermally fused, as good as solid pipe. Depending on the install, couplings in the run may be needed (not in my case) and they are always thermal fused, same process as buried plastic gas line. Again no concern with the joints leaking. The area with the manifolds was filled with screenings as well to minimize settling, etc.

In the second heating season and it is working even better than last year. Soil settling, etc has provided better soil coupling. Now in the second week of a real cold stretch (overnight single digits) the incoming water is still at 45 deg F. No problem maintaining 70 deg in the house at 0 deg outside, with no auxiliary heat.

paul