"Here is another geothermal data point for you:
My new home heating load is ~30,000 BTU and cooling load is ~26,000 BTU (2150 sq ft ICF over 1500 sq ft ICF basement). I sized my loop field for these loads and a Climatemaster TE 038 (3 ton 2 stage geothermal package unit with variable speed loop pump included). I used the Climatemaster Geodesigner program for the loop sizing.
3 vertical bores, 4.5" diameter x 230' deep, plus 20' of trench to the house. I can rent a trencher for ~$100/day to dig the trenches to the house. The cost for drilling and grouting the holes is $6/foot or $4140. The geothermal pipe (HDPE 3/4" x 510' with pre-installed U-bend) locally costs ~$160 per loop or $480 total. I'm estimating another $300 or so for inside header, valves, and piping to get to the geothermal unit. A Climatemaster TEV038 unit costs ~$7400 delivered. That is a total cost of ~$12,500 for a 3 ton 2 stage geothermal excluding ductwork and thermostat which I also plan to DIY. Given the current 30% tax credit, my net cost will be ~$8750."

Thanks for all those details. I'm envious of your low cost drilling. I asked here and the costs are way larger than that.
ICF is quite cool it was my first choice but I was not sure if I can afford with the expensive concrete here so I did not took the risk.

 
"Per the Geodesigner program, my local deep earth temperature is 63F with minimum EWT of 42F and maximum EWT of 96F for the above amount of load and loop given the expected geology (~30' of clay overlaying saturated shale with intermittent sandstone).  Annual average heating COP was 4.80.  A good portion of my hot water would also be generated by the heat pump."

How do you get that 4.8 COP is that estimated by software ?
That earth temperature variation seems to large to me. At that sort of depth over 200ft I expect a much more constant temperature with almost no dependence to season. Those numbers are probably calculated for that sizing program and if so I think those are a bit to large you probably need more ground loops for that load. (This is just a guess maybe someone else more informed here can help).
I took a look at the TE 038 it look like a nice unit with dual stage a bit expensive maybe and not sure how much warranty you will get for that unit.
Anyway with EWT around 40 to 50F and EAT of 70F I see a COP of around 4 to 4.5 still quite good and it seems to be the most efficient model they have.
They also mention that antifreeze is recommended at those temperature levels 40F and below they say they used 15% antifreeze solution for those.
Not sure is worth the extra cost vs the lower efficiency 3 to 3.5 COP units.

My electricity cost is ~10.5 cents / kWh all costs included.  Geodesigner estimated an average monthly heating / cooling / hot water cost of $59 or $705 per year.
 
With this combined heating and cooling is hard for me to do a comparison since I do not know the amount represented by each.
It may be half the energy for one and half for the other but it may be quite different.
Since this numbers are from Geodesigner they are probably based on a COP of 4.8 and if I assume 50% of this is heating (I may be quite wrong here) $705/2 = $352 then $352/0.105 = 3095kWh for the geo and with that 4.8 COP from the program is 14856kWh of heat energy.
Cooling with a simple inexpensive AC may be quite similar I do not expect much savings.
You mentioned your cost is about $8750 I think for $2750 you could have had a nice AC and direct electric heating so this makes for $6000 extra investment.
Heating with geo as assumed before 50% is $352 and over 10 years is $3520 + $6000 total $9520
Say you have used the direct heating for 10 years that will have been $352 x 4.8 x 10 = $16896 that is about 7000$ savings for geo so you can get a new heat pump for the next 10 years.
Things seems a bit optimistic but it dose seems this will be a cost effective investment even with 10.5 cent/kWh. That 30% tax credit helps also quite a bit and the fact that you want to do part of the work.

I wish I could have here drilling done at those sort of prices. Even if that was the case I will still stay with direct PV heating since I like solid state things more (no moving parts) is more reliable and I can not afford to be without heating here.
Is also that mentioned possibility to use the extra energy for other things.

OK I will say geothermal can be still a viable solution especially in places with more expensive electricity 20+ cent/kWh you just need to calculate the costs.
I can mark this topic as closed.
Thanks to all that participated.

Posted By electrodacus on 20 Mar 2015 08:09 PM
Not sure what liquid are you using since is close to freezing maybe is not water.

20% methanol. Heat capacity 3%-ish lower than pure water.

1 US_gallon-°F/min = 485 BTU/hr = 142 watts.

8 GPM x 7°F x 485 = 27.2 kBTU/hr = 8 kW

1800 x 1.12 x 4 = 8kW

Congratulations, your calculator works, BUT your answer is wrong.
8 kW is just the heat extracted from the loop. You ignored/forgot
the electrical power used to run compressor, blower and circ pump.
That all shows up as "electrical resistance heat" inside the envelope.

Conservatively, my Waterfurnace ND038 (running in stage 2), will
have a COP of about 4.0 (for EWTs in the 40°F vicinity). However,
my system normally runs in stage 1, where COPs are even higher.
(Waterfurnace specifies COP 4.58 @ 40°F EWT, 8 GPM, stage 1.)

But sticking with stage 2 @ COP 4.0, 8 kW heat of extraction yields
10.7 kW total output, with only 2.7 kW purchased from the grid.

In order to find out the average COP you will need to monitor ... blah, blah,blah

Sorry, in order to do that I would have to care. Best I can tell you is
that in February 2009 we used an average of 57.1 kWh/day total.
That includes heat, hot water, lighting, cooking, laundry, TV, and
tormenting the cat. Thermostat pretty much glued to 70°F (24/7),
2200 sqft living space over 2000-ish garages/basement/utility room.
1950's stone & concrete block construction. Decent insulation for its
age after major renovation in 2001 (but no upgrade to the old HVAC).

I was expecting someone has done a more scientific test related to cost amortization

Folks with a basic grasp of the difference between "huge" and "tiny"
routinely make "scientifically" valid estimates and decisions without
the bother of calculating everything to 0.01% (pseudo)accuracy.

With winter coming on, our 30-year-old oil furnace was nearing death,
(and our ancient central AC had recently expired). This was summer
of 2008, with fuel oil moving toward $5/US-gallon, and the (second!)
GWB market-meltdown just getting underway. My choice was to spend
big bucks to continue burning $5/gal oil (and to replace the air/air AC),
or go with geothermal. No natural gas available. Location not suitable
for solar -- steep, shady valley surrounded by tall oaks & poplars --
not to mention the much higher PV prices back in 2008 & 2009.

Hmm, ponder, ponder... combustion-free 4+ COP (w 30% tax credit),
OR yet another stinky $5/gal oil furnace plus noisy outdoor AC unit,
OR incentive-free resistance heating with electricity from the grid?

...you need more "analysis?" Really?? Gimme a freakin' break!

Looby

I had a similar situation; AC too old and oil burner needed replacement as well. The oil tank was starting to leak. I figured to replace all this (nat. gas is not available) would cost me about $20K in SE PA. Why bother? I had a 2Ton CM TEV 30 2 stage system installed with 3 bore holes; 150'deep and it's working well. This past year I used about $300 more electricity than in previous years but NO OIL! Oil was costing me $4.00/gal. I saved about $3,500 in oil over the year I've had the system, the AC is amazing in the summer, and we're more comfortable in the house. Obsolete? I don't think so!

I'm glad you consider the topic closed and I'll be glad to as well, but I regret I felt obliged to point out the following in your comments since yesterday.

Yes that is the main question. I know geothermal will not work for me. But I do not see it working for those that have grid power at 12 cent/kWh maybe at 40cent/kWh will make more sense do to higher savings more rapid recovery of investment.

It has been conceded geo isn't a good fit everywhere. Your premise asked if it's good anywhere.

Thing are quite different. Making distilled water in winter will not take anything from heating and in summer if you do not use the energy available is just lost energy.

Kind of like a DSH in the summer eh?

"Obsolescence frequently occurs because a replacement has become available that has, in sum, more advantages than the inconvenience related to repurchasing the replacement"

This is the part of the definition I'm referring to.

Ah, so by more advantages we mean no cooling, but we can distill water....sweet.

I'm an engineer I'm not happy with just an yes or no answer I want the numbers (all numbers).

No you want numbers that support your premise. Those offered that are inconvienient to your argument are disregarded or you ask others to do research for you.

Can you give more detail how did you calculated the COPin your system? It is for sure possible but a bit unlikely unless the ground loop is oversized

Case in point. On what basis have you determined the loops must be oversized to achieve 4 COP?

"Did the additional 500 SF also save on the heating bill?"

The additional thermal isolation can more than compensate for that small increase in living space.

This is perhaps my favorite example of your departure from reality. Did a rational person with a 750 square foot home just refer to a 500SF addition as a small increase in living space? Really!? Wouldn't it in fact if it was your neighbor have about 2/3rds or more of your heat load?
If one adds a third again as much to anything (old house was 1500 SF) is that a small increase?

Bio-diesel was more cost affective and continent for me

Yes hardly burned any fuel (to bad it didn't heat the house). Glad to know it holds its water.

I never considered tax credits. Are there good tax credits for geothermal ?

You don't consider (or research) lots of things.

I think the best way to see things from my perspective is like this.

Most folks don't see things from your perspective on purpose. Most would agree little cabins in the woods as a primary residence are by and large obselete.

If electricity was at 40cent/kWh or more like in some places you will not say is to cheep to meeter.

If, If, If.

Thanks for all those details. I'm envious of your low cost drilling. I asked here and the costs are way larger than that.

That's why most don't make blanket assumptions and assertions (costs and conditions vary).

That earth temperature variation seems to large to me. At that sort of depth over 200ft I expect a much more constant temperature with almost no dependence to season.

Yet another hole in your research. While undisturbed ground temps are quite stable, they are not undisturbed if you are harvesting or rejecting btus into the earth. Those who really know geo know that while one could put enough loop into the ground to stay near undisturbed temps, cost v benefit favors a designed fluctuation (usual parameters are around 30-90F).

They also mention that antifreeze is recommended at those temperature levels 40F and below they say they used 15% antifreeze solution for those.
Not sure is worth the extra cost vs the lower efficiency 3 to 3.5 COP units.

Again a transparent lack of geo education. 2 choices: put many more feet of pipe in the ground to keep water well above freezing at much higher first cost or pay a few bucks a year extra on operating cost but save thousands in first cost. BTW 3-3.5 COP units also require antifreeze in the loops anywhere the more efficient units do.
Frankly I've already spent too much time on this but I will offer you a little extra education. In an area where heating is dominant and kwh cost is in the neighbor hood of 10 cents US the op cost loss of a half COP may often be less than $100/yr.
Further to answer another question for you, one would want to buy a unit that qualifies for the tax credit wouldn't one? Some of the lower efficiency units do not.

Say you have used the direct heating for 10 years that will have been $352 x 4.8 x 10 = $16896

Is there no installation or equipment cost here for your heating system?



I do wish you well on your project and am quite agreeable to the assertion that what you have selected is best for you and your home. One contractor I knew stayed with his fuel oil steam boiler on purpose. He was replacing many oil furnaces and he heated his home with his clients' left over oil for no more than the cost of pumping and transport. He would argue that (at least for now) oil is better than everything else for heating his home.

"Ah, so by more advantages we mean no cooling, but we can distill water....sweet."

What I was trying to say is that savings from a simple and inexpensive AC to Geothermal cooling is very small. AC is extremely inexpensive compared to a geothermal heat pump at least this is my impression. So maybe a separate AC is even good if you have geothermal as a way to protect the heat pump but using it less hours (Not sure if this makes sense or not)
When I calculated the amortisation cost for PV I included just heating so in the summer months the PV will have been unused so any use of that free available power will help offset the investment cost.
Also any use of the available electricity in winter will result in heating so if I use the PV power to heat the floor or use part of that for distilled water the result will be the same amount of heating in the house.


No you want numbers that support your premise. Those offered that are inconvienient to your argument are disregarded or you ask others to do research for you.

No I want any numbers as you see I was even ready to accept theoretical numbers as one of the last replay that closed this tread.
I will have preferred measured numbers but probably not many care that much about this subject.
As an example of the things I expected is this 7 day graph that I made for my PV energy production consumption. The PV array is 720W



"Case in point. On what basis have you determined the loops must be oversized to achieve 4 COP?"

I may have used the wrong words here maybe correctly sized was a better choice.
It depends also on the type of loop vertical or horizontal even if I see here is mostly used with deep drilled holes.
Also I was not looking at the more sufficient more expensive dual stage heat pumps it seems those are more efficient but also quite a bit more expensive.
My impression was that the largest investement was in the ground loop and lower investment was done in the heat pump but the opposite seems to be true at least from the feedback here.


"If one adds a third again as much to anything (old house was 1500 SF) is that a small increase?"

You take this out of context. Yes he increased the house size but also insulated an old house (no mention on the old insulation or the amount of new insulation) That thermal insulation was probably more than compensated for the increase in size.
A house also dose not require directly proportional heating with the increase in size since the surface of the house envelope dose not increase by the same amount.

 
"Yes hardly burned any fuel (to bad it didn't heat the house). Glad to know it holds its water."

Yes I barely burned any fuel but I know the price of the fuel and the efficiency of the diesel burner. I do not need to know anything else to compare this with other fuels.

 
"You don't consider (or research) lots of things."

I never consider this because I feel this are unfair advantages. But most people will use them so is a fair point that they need to be taken in to account.
I did not claimed I did extensive research it was a question and I used this forum for research.
I'm sure solar PV also has incentives but I do not care about them personally.

If, If, If.

I was thinking on a more global scale. The 40 cent/kWh and above is normal in may European countries.


Yet another hole in your research. While undisturbed ground temps are quite stable, they are not undisturbed if you are harvesting or rejecting btus into the earth. Those who really know geo know that while one could put enough loop into the ground to stay near undisturbed temps, cost v benefit favors a designed fluctuation (usual parameters are around 30-90F).

I do not think disturbed soil makes any diffidence when you have the loop in ground water at that depth. This will apply way more to horizontal loops that it dose not seems to be that popular here.

 
"Further to answer another question for you, one would want to buy a unit that qualifies for the tax credit wouldn't one? Some of the lower efficiency units do not."

That seems to explain why people go for the more efficient more expensive units.


"Is there no installation or equipment cost here for your heating system?"

There is and was mentioned somewhere in there I think $2750 was considered if I remember correctly.

Posted By electrodacus on 21 Mar 2015 01:33 PM
I do not think disturbed soil makes any diffidence when
you have the loop in ground water at that depth.

Fortunately, (or not), the physical universe doesn't give a rat's rump
about what mere mortals "think." Most folks would be reluctant to
expound on "flaws" in the Geodesigner software before acquainting
themselves with even the most rudimentary facts of geo design.

Alas, lots of precise calculations and pretty graphics aren't much
help when you don't know what you're talking about.

Looby

"Alas, lots of precise calculations and pretty graphics aren't much
help when you don't know what you're talking about."

Do you want to say that you can change in a significant way the underground water temperature around that vertical loop 200 or 300ft deep?
I do not know how disturbed soil is a problem when we are talking about a 4" diameter over 200ft deep drilled hole and that loop is probably surrounded by water.
So not sure what you want to say by "you don't know what you're talking about."

Also your signature is this "One measurement is worth a thousand expert opinions."
This is what I will also want to see instead of predicted gain based on Geodesigner but I do not see anyone here bothered to do measurements on real installations.
My "pretty graphic" is just that measurement on the energy output of my real installation even if not for geo is for my PV array.
If I had a geothermal installation I will for sure have installed a flow meter and temperature sensors so I have an idea of the real gains.

Posted By electrodacus on 21 Mar 2015 04:23 PM
Also your signature is this "One measurement is worth a thousand expert opinions."
This is what I will also want to see instead of predicted gain based on Geodesigner
but I do not see anyone here bothered to do measurements on real installations.

Dead wrong, bucko. I gave you actual measurements: "Winter EWT: 37°F to 45°F"
and my location: "Philly 'burbs" -- where the undisturbed deep ground temperature is
approximately 53°F. But, as with other data that doesn't support your preconceived
and invincibly erroneous conclusions, you chose to ignore the facts and instead insist
that the Geodesigner™ software -- verified over tens of thousands of engineer-hours
of in-the-field observation, testing, and refinement -- must be hopelessly defective.

...there are none so blind as those who will not see,

Looby

"Dead wrong, bucko. I gave you EWT measurements: "Winter EWT: 37°F to 45°F"
and my location: "Philly 'burbs" -- where the undisturbed deep ground temperature is
approximately 53°F. But, as with other data that doesn't support your preconceived
and invincibly erroneous conclusions, you chose to ignore the facts and instead insist
that the Geodesigner™ software -- verified over tens of thousands of engineer-years
of in-the-field observation, testing, and refinement -- must be "defective.""

What you gave me was power. For energy I need power over time and requires data logging for some period of time since your power will change over time.
Also EWT will depend on how much power are you using at that time how large is the surface of the loop not just ground temperature. Just run the pump for the loop and stop the heat pump and your EWT will be the same as ground temperature.
It has nothing to do with ground being disturbed in this case since there will be water in the place ground was disturbed.
I have zero experience with Geodesigner and I do not think I mentioned anything about that software being defective.
As any software it will approximate the output based on the available input data. Since a geothermal installation is relatively complex there are many thing in real life that may change the predictions made with any software tool.

Posted By electrodacus on 21 Mar 2015 06:32 PM
Just run the pump for the loop and stop the heat pump and
your EWT will be the same as ground temperature. It has
nothing to do with ground being disturbed in this case
since there will be water in the place ground was disturbed.

Okie dokie, geo guru. Whatever.

What I was trying to say is that savings from a simple and inexpensive AC to Geothermal cooling is very small. AC is extremely inexpensive compared to a geothermal heat pump at least this is my impression. So maybe a separate AC is even good if you have geothermal as a way to protect the heat pump but using it less hours (Not sure if this makes sense or not)
When I calculated the amortisation cost for PV I included just heating so in the summer months the PV will have been unused so any use of that free available power will help offset the investment cost.
Also any use of the available electricity in winter will result in heating so if I use the PV power to heat the floor or use part of that for distilled water the result will be the same amount of heating in the house.


This entire paragraph boggles the mind. Savings on cooling is inconsequential to you but savings on bottled water is relevant. This is the kind of thing where if you are truly here to research, you need to open your mind.
Cooling is less expensive with geo. Is it compelling enough to buy geo in heating dominated climates? No, but it is it still weighs in on the equation. Further there are examples of people heating the pool while cooling the home further amplifying the benefit of geo.

"Case in point. On what basis have you determined the loops must be oversized to achieve 4 COP?"

I may have used the wrong words here maybe correctly sized was a better choice.

?? Again; baffling?? Was it your impression that we were espousing the virtues of geo without correctly sized loops?

It depends also on the type of loop vertical or horizontal even if I see here is mostly used with deep drilled holes.

Wives tale. No correctly sized loop is inferior to another. Verticals are more efficient in that we use half as much pipe to extract a similar amount of btus, but that does not make them better, in fact because they cost more, they are our least favorite option. I think you also try to express that it is your impression that vertical loops are most common and that again is incorrect. You should employ larger samples in your research (i.e. don't base your PV conclusions on one little house or your vertical loop conversions on a couple contributors to this thread).

Also I was not looking at the more sufficient more expensive dual stage heat pumps it seems those are more efficient but also quite a bit more expensive.
My impression was that the largest investement was in the ground loop and lower investment was done in the heat pump but the opposite seems to be true at least from the feedback here.

The ground loops may or may not be the most expensive part of the system depending on a variety of factors. Difference between a least efficient geo and most efficient may be as much as $4,000 if you pick a Water Furnace series 7 vs a Chinese mail order product, but for the most part the difference between a single manufacturer's builder's model to their flagship is 2-3K.


"If one adds a third again as much to anything (old house was 1500 SF) is that a small increase?"

You take this out of context.

Pot calls the kettle black, you changed the context. I asked this "Did a rational person with a 750 square foot home just refer to a 500SF addition as a small increase in living space?" before closing with that.

If, If, If.

I was thinking on a more global scale. The 40 cent/kWh and above is normal in may European countries.

That's fine but you must be reminded again that you set the context when you asked if geo heating is obselete. We are giving you cases where it is quite viable and you say what if. No one here has suggested geo is the best fit everywhere, but you have suggested it may not be a good fit anywhere. So in fairness the "what ifs?" are ours to employ not yours.

I do not think disturbed soil makes any diffidence when you have the loop in ground water at that depth. This will apply way more to horizontal loops that it dose not seems to be that popular here.

Another misconception (you really have a long way to go to understand geo). First not every loop is in ground water. Second if it is in ground water that doesn't mean it's completely in it (i.e. a vertical loop that passes through an aquifer but is by and large surrounded by rock). Third even if completly in ground water that temp can change seasonally.
No the swings are not necessarily greater on horizontals if correctly sized and I already covered that verticals are not more popular.

"Is there no installation or equipment cost here for your heating system?"

There is and was mentioned somewhere in there I think $2750 was considered if I remember correctly.

But that's for a house your size right? While many DIYs don't mind installing a package system, many arent equipped to install a split unit.

Do you want to say that you can change in a significant way the underground water temperature around that vertical loop 200 or 300ft deep?
I do not know how disturbed soil is a problem when we are talking about a 4" diameter over 200ft deep drilled hole and that loop is probably surrounded by water.
So not sure what you want to say by "you don't know what you're talking about."

Perhaps I can help you understand what you don't. The typical geo loop is not completely surrounded by water (in fact I can't imagine any that are) and is usually a 3/4" or 1" u-bend. So we will change the temp of whatever water we contact, but we will also change the temp of whatever soil and rock we contact. Water tends to flow so it can recover temp quickly but heat moves more slowly through soil and rock so disturbed soil will not remain at constant temp. Vertical loops are designed the same as horizontals (generally 30-90F).
BTW you could put enough loop into the ground so that you barely disturbed the temp and there is a moronic engineering firm that designed a high profile system that way. Added first cost was in the millions. Benefit in the thousands.


Just run the pump for the loop and stop the heat pump and your EWT will be the same as ground temperature.
It has nothing to do with ground being disturbed in this case since there will be water in the place ground was disturbed.

Covered this before but worth revisiting. Stop the heat pump and your EWT will shortly be the same as the disturbed ground temperature. It has everything to do with the ground being disturbed because in no case I've heard of (aside from pond loops) is the loop completly submerged.
You seem to envision a borehole filled with water that is constantly flowing. Picture instead a few veins of water in a bore through rock. The ground loops are then grouted to avoid cross or surface contamination of aquifers. So on a 150' bore you may only have 10' in contact with water.....Or a little more......or none at all.

If you came here truly to research then begin to search different topics and learn how geo works. People here are willing to help someone learn, but no one here wants to reprogram someone who asserts misconceptions as facts while demanding data all under the premise that geo technology isn't viable anyway. Thats where the responses begin to appear a tad hostile. More than once I have commented that is why you are getting so much push back.

Imagine if you came here and started a topic "is geo right for my home?" people here have already said PV sounds like a good fit for you. Then if you said something like "but I thought the ground temp was stable why does it fluctuate?" You'd learn the same without snarkiness attached. Imagine if youu accepted sometimes that others know what they are talking about without demanding numbers.

Many of us monitor our systems, but few of the pros monitor for COP. Here's why..... Nobody cares. What people care about is whether or not their savings is what the model (such as geodesigner) promises. Those in the biz know a few things i.e. manual J is full of fat to cover extreme days, so predicted balance point (temp at which auxiliary must assist the heat pump) should be higher than actual.
Meaning if I have a model that says my average COP should be 3.9 and my balance point should be 15F but my monitor shows me I'm actually not using the auxiliary until 5F Then all things on the operating cost model must be met or exceeded. To my customer, it costs less to run than predicted or no more. They don't ask what the COP was and as Looby illustrates,
they don't pay any attention at all to it after a year or two.
So COP could be monitored, but I like to watch first stage, second and auxiliary and I like to get emails from the monitor if something is wrong. I like to experiment with constant fan and other things to try to lower balance points. I like monitoring outdoor temps and wind speed and have learned how different insulations perform in the wind to sharpen our designs.
I can do all this on a Wi-Fi thermostat for a few hundred bucks, but it won't tell me COP.....Nobody cares.
So yes I monitor, but the aquired data is of great use to me but not to a geo skeptic.

Thanks for taking the time to give such an detailed feedback.
I consider this case close and I will not make a replay to everything. (geothermal is not obsolete at this point and may be a good investment in many cases)
If title seems "annoying" I can change that if it helps. How should I change that ?
You made a lot of good points like heating the pool while cooling the house.
As for disturbed ground related to bore holes. My view is that once you drill a hole 200 to 300ft deep you will have a good chance to find one or more underground water reservoir and that hole will fill with water to whatever the ground water level is in that area.
I do not know how you fill that narrow hole after you insert the loop (I assume you use sand but I may be wrong) anyway water will surround the ground loop up to a certain level it may be half the loop more or less.
But since water is not stuck there and has great thermal conductivity compared to sand or whatever is around the pipe the rest of the way that will probably contribute the most and the rest of sand or disturbed soil is "irrelevant" less relevant in the total.
I may be wrong and I appreciate an answer to this but this was my impression when I was saying that disturbed soil is not a problem in vertical loops.

The hole is grouted with bentonite (montmorillonite) which is a clay mineral. It's added as a slurry, fills in around the pipes and serves to conduct the heat and fill the hole; at least that's what they did in my installation.

"The hole is grouted with bentonite (montmorillonite) which is a clay mineral. It's added as a slurry, fills in around the pipes and serves to conduct the heat and fill the hole; at least that's what they did in my installation."

Thanks for replay is what I imagined something like a very fine powder.

Posted By electrodacus on 22 Mar 2015 01:44 PM
But since water ... has great thermal conductivity
compared to sand or whatever is around the pipe ...

Material ................. W/m-K
saturated sand ...... 2.0 to 4.0
moist sand ............ 2.1 to 2.3
sandstone ............. 1.8 to 3.9
granite .................. 1.7 to 4.0
schist .................... 1.4 to 2.4
limestone .............. 1.2 to 1.3
moist soil .............. 1.0 to 1.4
liquid water ........... 0.6

Often in error, but never in doubt.

"Material ................. W/m-K
saturated sand ...... 2.0 to 4.0
granite ................... 1.7 to 4.0
sandstone ............. 1.8 to 3.9
limestone .............. 1.2 to 1.3
moist soil ............... 1.0 to 1.4
liquid water ............ 0.6

Often in error, but never in doubt."

I know all this numbers. Water in this case is moving and also water is the one that helps soil and sand have a better conductivity (dry sand or soil will have 0.2 to 0.5).
And granite or stone without water will not be able to contact the round pipe used for the loop.
But what helps water the most is that it can move and has a higher heat capacity.

Posted By electrodacus on 22 Mar 2015 03:23 PM
And granite or stone without water will not be able to contact
the round pipe used for the loop.

I guess you have never heard of bentonite grout, huh?

let's let this thread die ???

Amen!!