What is the Straight Dope of Geo-Thermal Heating and Cooling?

Factual Questions
21

[QUOTE=Labelless]
Sure! It was $13,500 for everything. That was removal of the massive unit that was there before, a new pump for the well to keep up with the water demand, complete installation. Ours doesn’t include the basement or the garage in the Sq. Ft either.
And total time spent on the project, about a week. We had to wait for the unit to be built and shipped from Florida, took about two weeks for that, but ground breaking and install was a snap.

Figaro, When our specialist came in, they did tests to check the house for a compatibility rating basically, and our quotes were drawn up upon that. They did some number jumbling with expected heat loss and the like. I don’t know about a guarantee per se, but they were very professional and checked all spaces in the house. They also explained the differences in the models, and why we needed that ton-age for the house we had. While the 3 ton was going to do the job, the 4 wouldn’t work as hard, and be more efficient. And the cost difference wasn’t enough for us to consider the smaller unit.

Yes, I called my husband and he confirmed we got the 4 ton.
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I’ll let the pros figure it out for me, but as a rough guess I have a greater cooling requirement and a smaller heating requirement and less house to deal with. I am probably looking at a 3 or 3.5 ton unit. I think my AC is a 3 ton, but I need to verify tonight.

I am still a little vague from the answers but along with eliminating the need to burn oil what is the overall effect on the total year electric bill? It looks like I would use more in the winter but significantly less in the summer and possibly get an additional savings for the year from my water heater not needing to run or not needing to run as often.

22

I’m sorry I’m being vague. We just got it installed two months ago, and our electric bill isn’t reflecting much because we’re moving in this weekend.

But after a quick call to my grandfather, (who gave me the idea for geothermal in the first place,) he’s had his for about two years now. They’ve always had the Time Of Day meter for electric. After a few months of tinkering and adjusting, he’s evened out with an average bill of $68.00 in the summer and $80.00 in the winter. His home is about 1800 sq. ft. They also bought a timer to shut off the water heater during the day, and turn on in the late afternoon, though he’s considering getting the tankless water heater. They keep the average temp in the summer at 75 and in the winter at 69.

I hope that helps a little more.

23

[QUOTE=danceswithcats]
From what I’ve read, there are two different styles of geothermal. One uses drilled well(s) with a glycol solution circulated through them and a heat exchanger. The other uses a series of copper ground loops through which the refrigerant is circulated, eliminating the efficiency losses of a heat exchanger.
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Actually there are several. The geo unit itself is essentially the same for all of them. The heat exchange loop will really be different. The basic options are drill down as a well; dig a huge 6’ or so pit and go horizontally; recirculate your well water; drop a horizontal system into a lake or pond. In no case was copper an option. My horizontal, 6’ depth ground loop is a PVC-type material. Not PVC, but I can’t remember what it is. Copper of course is a better heat exchange medium per square unit of measurement, but it’s cost prohibitive these days. A longer even if less efficient material will provide the same heat transfer.

What Exit?, don’t forget to look into special rates for the second meter for the system. Also, we didn’t have a state energy rebate, but I got the federal tax credit. It’s since expired, though, and it was only $300 anyway.

Also, while my meter is a “time of day meter,” because of the rate plan, it’s the same price all 24 hours. It’s also uninterruptible service, meaning I’m paying less than the people on the interruptible AC plans, with no chance of losing power during rolling AC blackouts (not that there’s much of a history of that anyway here).

My original payback calculations were slated at four years. Note that that was compared against another replacement, high-efficiency system. That is, the original projection for the cost recovery of the geo versus purchasing a conventional, high-efficiency system was four years. Honestly, I’m sure I’m going to significantly beat that, though. All of the numbers that I supplied for the analysis were based on low consumption from not actually living in my house (I spend one year periods of time on the road).

24

[QUOTE=Labelless]
I’m sorry I’m being vague. We just got it installed two months ago, and our electric bill isn’t reflecting much because we’re moving in this weekend.

But after a quick call to my grandfather, (who gave me the idea for geothermal in the first place,) he’s had his for about two years now. They’ve always had the Time Of Day meter for electric. After a few months of tinkering and adjusting, he’s evened out with an average bill of $68.00 in the summer and $80.00 in the winter. His home is about 1800 sq. ft. They also bought a timer to shut off the water heater during the day, and turn on in the late afternoon, though he’s considering getting the tankless water heater. They keep the average temp in the summer at 75 and in the winter at 69.

I hope that helps a little more.
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Thank you again and I don’t think you were being vague. I am just confused and trying to come up to speed quick on something that 6 years ago seemed too expensive to bother installing. The huge savings will be on not burning oil. This is also a big plus environmentally. I think there will actually be a net savings in electrical usage. That would be gravy but I am curious about it.

Jim

25

[QUOTE=What Exit?]
I think there will actually be a net savings in electrical usage. That would be gravy but I am curious about it.
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I don’t know about a net save on electricity. Right now, what do you spend for electricity for your HVAC system? For heating, since you have oil baseboard heat, what electrical costs do you have (really, I don’t know… how’s that even work? Electric pump or something?). For cooling, you have your fan blower, compressor, evaporator fan, and pump. For hot water, you have electrically heated hot water.

With geothermal, you’re now adding electricity in the winter for heating, in order to run the pump, compressor, and fan. You’re automatically adding more electrical usage. Will this be offset by hot water savings? It has a COP of 1, whereas geo for your environment will be about 4. Specific heat and volume of water versus air – I won’t calculate all that, but I’m guessing it’s cheaper to heat your water than your house. Plus you’re still heating water when you’re not running the geo.

Now with discounted pricing for geo, there’s a possibility that your costs (not your usage) may drop, especially if you have a discounted rate for geo-cooling that you don’t have now. I’ll have to do an analysis in my own case to see if that’s true or not.

26

[QUOTE=Balthisar]
I don’t know about a net save on electricity. Right now, what do you spend for electricity for your HVAC system? For heating, since you have oil baseboard heat, what electrical costs do you have (really, I don’t know… how’s that even work? Electric pump or something?). For cooling, you have your fan blower, compressor, evaporator fan, and pump. For hot water, you have electrically heated hot water.

With geothermal, you’re now adding electricity in the winter for heating, in order to run the pump, compressor, and fan. You’re automatically adding more electrical usage. Will this be offset by hot water savings? It has a COP of 1, whereas geo for your environment will be about 4. Specific heat and volume of water versus air – I won’t calculate all that, but I’m guessing it’s cheaper to heat your water than your house. Plus you’re still heating water when you’re not running the geo.

Now with discounted pricing for geo, there’s a possibility that your costs (not your usage) may drop, especially if you have a discounted rate for geo-cooling that you don’t have now. I’ll have to do an analysis in my own case to see if that’s true or not.
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That is the tough part of the question. My electrical usage is muddied by Solar Power. I generate much more energy in the summer when I use the most. AC & Hot water and normal usage. My bills between the heating and cooling seasons have dropped as low as $8. $27 might be an expensive May or October.

As my Hot water heater is not particular efficient and my Compressor is old and thus probably very inefficient, I think I might save electrical for a full 12 month period.

As to the hot water baseboard, there is a small oil pump, a small blower fan for the firebox and two pumps to pump the hot water to the two zones. The total usage is low. I am not sure how low as I cannot isolate the circuit and I don’t have a good feel for run times.

So in the end I expect my summer electric usage to drop and my winter usage to increase.

Just to clarify, does the system heat the domestic hot water when it is acting as an AC unit?

27

[QUOTE=What Exit?]
My bills between the heating and cooling seasons have dropped as low as $8. $27 might be an expensive May or October.
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Holy cow! Are you on a separate meter? Even when I’m not home and everything is off, I spend more than that.

Not that I have anything to offer, but that makes sense to me know. It’s a hot water baseboard system, fired by oil. I don’t know why that didn’t click earlier. :smack: When I mentioned above how I had hated all forced air system until the one I have now, it was because I’d earlier been spoiled by hot water radiator heat. Awesome feel to the air with radiated systems, but with the low speeds, lower heats, longer run times, and a better humidifier, I have no complaints with my current forced air system.

Got you. It was the winter thing I was questioning, since, ya know, this is an electric system! Again it’s too early to gage whether my some consumption has dropped, but with my rate, I know for a fact that my costs will drop! (I’ve only been running the AC since last Thursday.)

The precise answer is you’ll have to check with the manufacturer of the specific system in which you’re interested. The common sense answer (true for my system) is that it will be more efficient when in AC mode than in heating mode, since you’ll be heating the water with the residual heat that you’re taking out of the air. That is, in winter, you’re sucking heat out of the ground, and putting some of it into the water tank, and most of it into the house. In the summer, you’re sucking all of the heat out of the house, and it doesn’t matter where you dump it – might as well put it into the water tank before piping the rest of it into the earth.

Get the technical documentation for the system that’s proposed to you. It will mention COP’s (heat), SEER’s (cooling), and relate all of that to volume of liquid, ambient ground temperature, and so on, and will include the COP’s and SEER’s for using desuperheaters or not. I’m not sure what you do for a living, but the technical documentation made sense to me.

A word of advice: also check with the planning department for your electrical utility. After the fact, I almost had to upgrade the electrical service to my house. No, not the service entrance, but the drop from the pole. This would have meant a transformer in my yard (not on the pole, not the edge of my yard in the easement, but in my yard!). It would have been free, but yuck! In the end after convincing them that I wasn’t dropping the line by more than 7 volts (I had to propose a chart recorder), they compromised by increasing the wire gage from the pole to my service drop. They look at the electrical data plate for the inrush current principally. Panicked, I consulted with my installation contractor, and he indicated he’s never had this problem before, so hopefully it’s rare. I think what ultimately swayed the planner was, I’d already had a 3.5 ton compressor; why would a more efficient 3.2 ton compressor finally start causing problems?

28

[QUOTE=Balthisar]
Holy cow! Are you on a separate meter? Even when I’m not home and everything is off, I spend more than that.
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The very low bills are because of my rooftop Solar Panels. They counter a good percentage of my usage. My worst bill only hit $95 last year.

29

[QUOTE=danceswithcats]
From what I’ve read, there are two different styles of geothermal. One uses drilled well(s) with a glycol solution circulated through them and a heat exchanger. The other uses a series of copper ground loops through which the refrigerant is circulated, eliminating the efficiency losses of a heat exchanger. One article described a radial boring unit placing holes around a central point on downward angles (think of downward facing daisy), those holes being filled with a protective grout, such that the copper isn’t subject to corrosive ground effects.
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I’m an HVAC guy, and I “inherited” a bunch of customers when a few Geo manufacturers and Geo contractors went belly up.

As to the difference of “Indirect” systems (those that use a gycol/water loop in the earth field) and the “Direct Expansion” systems (those that use copper loops and pump the refrigerant directly into the earth field) you should be aware of this:

  1. The average garden variety A/C unit (Non-Geo) has somewhere between 2 and 3 pounds of “Freon” per ton of cooling. As an example, then, a 3 ton system will hold between 6 and 9 pounds, typically.

A Direct Expansion system will hold [generally] between 8 and 10 pounds of refrigerant per ton. So…that same 3 ton system---- if it’s a direct Geo— may hold between 24 and 30 pounds of “Freon.”

If, you develop a leak in that system at some point in the future, the cost of recharging the system could be very expensive. Maybe I am biased by my experiences, but my Direct Geo customers stress me out. I hate being the bearer of bad news. Yesterday I put 16 pounds of Freon in a direct system. That’s $480 just for the Freon, before labor, truck charges etc.

The experiences have left me quite gun shy about direct expansion systems. Maybe because I’ve seen the worst of them, (after all, people aren’t calling me if they have no problems) but I’m quite reluctant to recommend or sell direct systems. (that’s my perspective from the field)

  1. “Freon” is simply one brand name (like “Xerox” is one brand of copier) of R-22. R-22 is being phased out in the next several years, and the price of Freon went up 79% this year. The newest refrigerant on the market is 410a, and it looks like the name that people will come to know it as (being, again, just one brand name) is “Puron.” If someone is looking to buy any A/C system, I would strongly recommend a 410a system.

My 200 pesos…

30

[QUOTE=the raindog]
A Direct Expansion system will hold [generally] between 8 and 10 pounds of refrigerant per ton. So…that same 3 ton system---- if it’s a direct Geo— may hold between 24 and 30 pounds of “Freon.”

If, you develop a leak in that system at some point in the future, the cost of recharging the system could be very expensive. Maybe I am biased by my experiences, but my Direct Geo customers stress me out. I hate being the bearer of bad news. Yesterday I put 16 pounds of Freon in a direct system. That’s $480 just for the Freon, before labor, truck charges etc.

The experiences have left me quite gun shy about direct expansion systems. Maybe because I’ve seen the worst of them, (after all, people aren’t calling me if they have no problems) but I’m quite reluctant to recommend or sell direct systems. (that’s my perspective from the field)
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Holy cow! I never realized these existed, which is why I thought I clarified danceswithcats’ answer. I didn’t realize he meant that actual refrigerant was passed through. Trust me; I did lots and lots and lots of research before making my own significant investment. The whole topic of DX never came up a single time. I wonder if they’re just not used anymore? A quick search indicates that DX systems have a very slight advantage in COP and SEER than antifreeze systems, but that’d all be lost with a singe line repair!

31

[QUOTE=Balthisar]
Holy cow! I never realized these existed, which is why I thought I clarified danceswithcats’ answer. I didn’t realize he meant that actual refrigerant was passed through. Trust me; I did lots and lots and lots of research before making my own significant investment. The whole topic of DX never came up a single time. I wonder if they’re just not used anymore? A quick search indicates that DX systems have a very slight advantage in COP and SEER than antifreeze systems, but that’d all be lost with a singe line repair!
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I only ever considered the anti-freeze system. I use to be an HVAC mechanic years ago and though I did not work on Freon units, I know the pitfalls of said.

I checked my Air Compressor yesterday and could not determine the tonnage. My BIL will be over Sunday, he has a blue seal and I will ask him to take a look. I think I have a 3 ton unit. It is a Ruud from 1994. My Boiler is either 100,000 or 120,000 BTU.

32

I’ve been trying to come up with the most efficient and cost effective way to heat my farmhouse. I’ve considered geo-thermal. I have plenty of land. But in TN, that land is rock about 6" down. I have a well already, but I doubt it’s very deep. I presently have no central heat and air. I have no ductwork, and a very small crawlspace (it might be high enough for the ductwork, but most of it isn’t high enough to crawl under). My walls have no bracing between the studs, so maybe ductwork could be run from the attic? I’ve worked at insulating the half that I live in, but it needs more. And, of course, I’m a poor single woman. I could take out a loan to cover the cost, but don’t want to incure too much debt. The money to repay it has to come from somewhere.

Being a grownup is hard.

StG

33

Probably the most efficient way to use a heat pump would be to sink 2 wells and circulate water between them. I have a buddy who is planning on buidling his own drill set up but there is a limit to how far an individual can sink a well. If you have a high water table it would be a doable project.

Here’s an HTML of a system using an existing well and 300’ of PEX. some of the print is in white so you have to highlight it to read it or convert to another color.

I don’t know much about PEX except there are different types with different fittings so add that to the research.

34

[QUOTE=Balthisar]
Holy cow! I never realized these existed, which is why I thought I clarified danceswithcats’ answer. I didn’t realize he meant that actual refrigerant was passed through. Trust me; I did lots and lots and lots of research before making my own significant investment. The whole topic of DX never came up a single time. I wonder if they’re just not used anymore? A quick search indicates that DX systems have a very slight advantage in COP and SEER than antifreeze systems, but that’d all be lost with a singe line repair!
[/QUOTE]

Indeed.

I would imagine that DX systems are a small fraction of overall Geo installs, with Indirect being much more common.

They are still sold, however, and there is a loyal, passionate group selling, and advocating for them. A few of the bigger names went bankrupt several years back. Of the DX customers I have, most of them have problems, with leaks being the most prevalent. The second, believe it or not, is the earth field heating up so much (in the summer) that it won’t accept any more heat. (and in the summer not having any more heat to give) I’ve even seen houses where the earth field was too close to the house, and in the winter it froze the ground so thoroughly it expanded and started pushing in the foundation walls.

One other observation/recommendation: make sure your Geo install has a “soaker field.”

35

[QUOTE=What Exit?]
I only ever considered the anti-freeze system. I use to be an HVAC mechanic years ago and though I did not work on Freon units, I know the pitfalls of said.

I checked my Air Compressor yesterday and could not determine the tonnage. My BIL will be over Sunday, he has a blue seal and I will ask him to take a look. I think I have a 3 ton unit. It is a Ruud from 1994. My Boiler is either 100,000 or 120,000 BTU.
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The tonnage will be in the model number. The units are sized in half ton increments with 12,000 being one ton. So…an “18” in the model number would be 18,000 btus or 1.5 tons, “24” being 24,000 btus (2 ton) and so forth: 18,24,30,36,42,48, up to “60” being 5 tons, typically the largest residential unit you can buy.

36

[QUOTE=the raindog]
The tonnage will be in the model number. The units are sized in half ton increments with 12,000 being one ton. So…an “18” in the model number would be 18,000 btus or 1.5 tons, “24” being 24,000 btus (2 ton) and so forth: 18,24,30,36,42,48, up to “60” being 5 tons, typically the largest residential unit you can buy.
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Thank you so much, the model is UAMA 048JAZ so it looks like it is a 4 Ton unit. Higher than I thought. I tried looking it up on Ruud’s website, but that had no information. Not too surprising for a 1994 model.

I think that is probably oversized for 2300 Sq Ft of Living Space.

What is a “soaker field”?

Jim

37

[QUOTE=What Exit?]
Thank you so much, the model is UAMA 048JAZ so it looks like it is a 4 Ton unit. Higher than I thought. I tried looking it up on Ruud’s website, but that had no information. Not too surprising for a 1994 model.

I think that is probably oversized for 2300 Sq Ft of Living Space.

What is a “soaker field”?

Jim
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As a general rule (and only a general rule; although a decent guide) you’ll get between 500 sq ft and 1000 sq ft per ton.

A poorly insulated home experiences a lot of heat infiltration from the outside and so may only be able to cool 500 sq ft per ton. A well insulated home has fewer thermal losses and I’ve seen houses with units at 1000 sq ft per ton.

At 2300 sq ft, you’re cooling 575 sq ft per ton, which suggests either your home is poorly insulated (attic, walls, windows, roof etc) or the unit is oversized.

Later generations of GeoThermal manufacturers learned (from the bitter experiences of early adopters) that a long and dry summer could result in the earth being “baked” in the field. In other words, so much heat from the home had been transferred to the earth during the summer that the earth wouldn’t accept it any more, or would become extremely inefficient . (think how efficient a standard A/C unit would be if it was 120 degrees outside. However, that’s the equivalent the Geos were seeing after a long, dry summer.)

The owners were advised to water their lawns. I’ve personally seen people put a sprinkler in the yard continuously for days on end. (with very limited success if at all, as the water wouldn’t leach down well below the frost line, where the coils were buried)

So…“soaker fields” were put in at the time the coils were buried. It’s essentially a perforated hose that is in the same trench with the glycol/ or refrigerant lines. It came up out of the ground near the house with a standard garden hose fitting. The owner could then hook up a hose and water the earth field directly, underground. The water would cool the field/earth and take away the heat. It is a very effective way to keep the Geo running efficiently.

38

I finally started making my calls today. We have decided to see this through.