Geothermal heat pump

[Cookie]

Did anyone watch Dirty Jobs? It demonstrated doing a thermal well, those people were amazing.

*I corrected what they called a thermal well to, Geothermal heat pump.

[speedbump]

What's a Thermal Well Cookie?

[Bill Arden]

Google: Geothermal heat pump

It's the cheapest way to heat or cool a building.

I have looked at adding them, but I don't have the money.

The well is drilled just like a regular well, except that plastic can be used for the wall. Others remove the pipe after drilling.

Either way you are left with a long piece of tubing that goes down ~100 feet and then loops back up the same hole. The tubing is generally cemented/grouted in place.

[Cookie]

Yep, that is it. It really was interesting and worth watching. Although, a really messy job, you got to love mud.:)

http://dsc.discovery.com/tv-schedules/series.html?paid=1.12301.25321.4062.x

[hj]

An offshoot of that process is to use two wells fairly close together. Pump water out of the first one and circulate it through the heat exchanger and then deposit it down the second one. The distance between the wells allows the water to stabilize to the ambient temperature. And since it is a closed system, there is no contamination.

[speedbump]

I have always referred to them as a Ground Water Heat Pump.

I am not so sure the claims made by some are all they are cracked up to be. I had one at a home I owned here in Florida and didn't see any substantial savings. There is certainly more maintenance to one over a conventional heat pump.

Your right Cookie, Rotary drilling is a messy profession. Drilling Mud is nasty.

bob...

[Rancher]

Bob,

I have one of those Ground Source Heat Pump, it's only 10' underground so no water is involved, in fact if they use the drilled well method and hit water, they must grout it and drill thru it, the well is then filled with crusher fines.

What is the extra maintence, I've done nothing in the past 12 years.

Rancher

[speedbump]

Explain how it works. I didn't get the part of no water is involved.

The ones I am familiar with usually involve a well, well pump, tank etc. Some have two wells. So the maintenance is the above additional equipment. Nothing lasts forever and there is always little things like bugs in the switch, waterlogged tanks etc.

bob...

[Rancher]

I forgot about all the extra pumps and stuff you need for the wells, my freon (R-22) goes out to the pit in 1-1/2" and 1" copper to a header system underground, 1/4" tubing covers a 50' X 50' pit, 10' deep, the ground is alwasy warmer for heat exchange than outside air is for exchange. It does have a water drip system installed on top of it, at the tubing level so you can add water for better heat exchange, I've never used it.

My forced air heat out of the register is at 102 degrees, what is yours?

Rancher

[speedbump]

My forced air heat out of the register is at 102 degrees, what is yours?

You could get second degree burns from that.

I don't have any idea how hot my registers air flow is. Without a heat strip and just using a normal heat pump, I would not think very hot.

I can paint a pipe black lay it on the roof and get the water up to 140° in the summer though.

bob...

[Rancher]

You could get second degree burns from that. Only if you stay out in the sunlight without sunscreen on, it gets to over 120 in the summer in Phoenix in the summer.


I don't have any idea how hot my registers air flow is. Without a heat strip and just using a normal heat pump, I would not think very hot.So you add heat (electric) to your heat pump, ... in Florida? I got me one of those IR thermal guns, less than $50, now I see them for $25, if you ever get the chance try em, they spot energy leaks real easy.


I can paint a pipe black lay it on the roof and get the water up to 140° in the summer though.
I agree, I can get my solar tank up to over 180 degrees in summer, those are glass faced solar panels.

Rancher

[Bill Arden]

The systems are more popular in cold climates like here in MN.

FYI: It's -10F here right now. :eek:

Here in MN there is one company trying to market a "air source" heat pump, but it's quite complex and expensive. Normal air source heat pumps don't work when it's cold out. I tried to get them to market it as a "portable" system where you own it like a car, but that would require them to re-program the computer so that it could also cool the water heat option it has.

The MN DNR rules don't allow you to use two wells, you have to either discharge at the surface or use what is called a "clean water drain field"

The "pump n dump" systems do have one drawback in that every few years you have to wash the unit out with a cleaning solution (like vinegar) to remove the mineral deposits.

The well and trench systems have very little maintenance, but cost more to install.

All in all These systems are best way to heat a house and when combined with low priced electric from either "Dual fuel" or "off peak" you get a very low cost way of heating.

I would put one in if I could afford it. :)
But I keep paying the ~$200/month for baseboard electric. :(

PS: This topic may be better in the HVac section. *You were right, Cookie

[speedbump]

I remember when the marketing got heated up in Michigan back in the 70's and 80's. They just never caught on. I don't know if it was over hyped or they just didn't work that well. And the initial cost probably made it prohibitive for some. But for my money, I would go with a plain old gas furnace if I were living in the tundra again.

bob...

[alternety]

Ground source heat pumps can be very cost effective. You have to use the COP (coefficient of performance) with the local electrical rate to see what a BTU costs. If you are going to use electric heat, the heat pump will always be cheaper to run. You get 2-3 X or more energy out than you pay to put in.

Generally speaking heat pumps are a good match for the temperatures used in in-floor radiant. Initial costs, as others have noted, are quite high. They also had real reliability problems for quite a few years before they got the hang of it. I would have used one here except for the initial cost and having concerns about quick repairs/parts. I also want to be able to provide backup power if services go down. Propane with a small generator is easier than a generator big enough for the heat pump (depending on the size of the heat pump of course).

They should always perform better overall than one using outside air in a northern climate for heating. Probably better for air conditioning almost anywhere. Much better temperature differentials.

[jdoll42]

Hey guys. I've got a ground source heat pump (geothermal). Been running it for over a year now. What they did here was put in 6 wells at 150' deep each. Then they ran some sort of special plastic pipe (pex maybe?) down each hole then back up again (closed loop). The way it was explained to me is that I basically have 12 lengths of pipe at an average of 75' deep. The ground temperature that deep here is about 58-60F year round.

So instead of using a compressor and fan outside to dissipate the summer heat with the hot outside air, it uses the 60-degree dirt instead. Since it's a heat pump, just reverse in the winter.

Even with all of this piping, there are only two small inline pumps mounted to the main unit in the basement. Each pump is about the size of a small coffee can. They are so quiet I can't tell when they are running.

One nice side of the system I have is it also makes my hot water for me. I use an electric hot water heater as a storage tank, so in weather when I'm not calling for much heating or cooling, the electric takes over.

If anybody has any specific quesitons about my setup, let me know. I absolutely love this system and have had no maintenance at all. No outside unit to clean each spring. Nothing. It's great!

[speedbump]

What was the initial cost for the entire setup including the wells?

bob...

[jdoll42]

It was a new house (about 3000 sqft), so here's what they installed:

-6 wells @ 150' deep each (totalling about 2000' of pipe)
-All new ductwork
-3 zones
-6 ton unit
-"Desuperheater" for hot water

Cost ran me about $26k. A high-efficiency propane split system (1 unit in basement for basement and 1st floor, 1 unit in attic for 2nd floor) was quoted at about $24k.

I wanted to comment on the wells. Around where I live they drilled though 150' of dirt, gravel, and sand. They didn't hit any rock or anything special. The well was bored about 6" diameter. They didn't use any casing or anything. As soon as the hole was as deep as they wanted, they inserted the plastic piping then backfilled the entire well with a bentonite slurry. They did all 6 wells in one day.

[speedbump]

That must be some really easy drilling to put in 900 foot of 6" hole in one day.

I'm no heating contractor, but that second quote sounds like an awful lot of money for what they quoted.

bob...

[jdoll42]

I'm not a well driller, so I have no idea if it was fast or slow. I do know they arrived about 6 am and pulled out around 8 pm. They probably had around an hour of setup and an hour of tear-down. I guess that puts them about one 150' hole every 2 hours. Is that fast? They just hit mostly dirt and clay with some light sand mixed in occasionally.

[speedbump]

Yup, that's fast. They probably don't even know what Flint and Chirt are. The drillers in my area are very aware of these two very hard rocks. Granite on the other hand isn't the softest material around either.

bob...

[jdoll42]

What is the approximate cost of your system?

Installation or operational? Complete install in a new house was around $26k. (See posts above).

As to the operational costs, I'd have to look at my bill for the exact kWh cost. I can tell you that my parents house is half the size of mine, has gas heat, gas hot water, and gas dryer, and their power bill is twice mine. (My house is 100% electric.) Their house is only 18 years old, so it's not like it's a 200 year old house with no insulation.

[jadnashua]

NH's nickname is the granite state...wells here are a major pain. They may end up deep, and then when you do get water, you may find it is full of radon gas, which isn't the nicest thing to have spraying out the showerhead (the heat releases it, and you suck it deep into your lungs, giving the radiation maximum detrimental effect!). that would be a multiple day affair here. Still, the local schools are thinking about doing it for an upgrade to the heating/cooling system as we have some of the highest utility rates in the country.

[gear junkie]

A customer of mine has a 4000 sq ft home and his electric bill was close to 250 a month. After he got geothermal, it dropped to 100 a month. I'm definently going to have it in my home and lots of government facilities are already starting to plan for it's use.

[jadnashua]

I use about 600KwH per month, and my bill runs about $85. My guess is that the electric rates there are a lot lower than mine! Ground source heat pumps are good. Around here, though, you find it hard to drill down, or have enough soil to bury them (even if you do have the acerage you want to tear up to install it that way).

[jdoll42]

I use about 600KwH per month, and my bill runs about $85.

I just checked my last bill. My usage for Jan. was 3598kWh. The first 2000kWh was at 0.08715 and the last 1598kWh was at 0.06272. My kWh charge totaled $274.53. I know it's not New England or anything, but we've been getting down to the teens most night and maybe breaking freezing during the day. Add the wind to that (I'm in the middle of an old horse pasture with no defenses from the wind) and my system seems to be chugging along pretty well most of the time. With that said, it RARELY hits second stage and I don't know if it ever touches the electric strip heaters inside the unit.

Looking at my historical usage, my worst months are Jan-Mar. However, in the summer my kWh usage barely exceeds 1200kWh, if even that much. That's trying to cool down 90-100F air with between 70-90% humidity down to about 72F.

[Bill Arden]

I've been trying to convince a directional drilling company to try what I call a "Star" configuration, but most charge by the foot based on drilling a few feet.

The concept is simple in that you make a pit and turn the machine in a circle drilling down at a angle with it set to curve upwards. You then use a back reamer to pull a pair of pipes back with a U at the end. You pull the far ends down below the frost line and then tie them together in the pit to make a series of radial fingers.

[Bill Arden]

I have the summary from the power utility. Since I use mostly baseboard electric the kWh follows heating.

kWh total for year =35,685
$ total for year = $2,442

Highest month = February
kWh = 6,590
$ = $397

So this shows that a heat pump would save me a bit of money.
I've found a used unit cheep and plan on using a "pump-n-dump" system using a shallow well and dumping the water in the yard.

[speedbump]

Be aware that some shallow wells have large amounts of iron. The tubing that exchanges the heat can become useless when clogged with iron. I know this first hand with the GWHP that I had about 12 years ago. It was a major pain. If you have pristine water or are going to recirculate clean water, this wouldn't be a problem.

bob...

[Bill Arden]

The water has iron... I am not far from the "iron range"

I just plan on cleaning it out using vinegar like others do.

It's a stepping stone to a closed system.

[speedbump]

Problem is, while this thing is getting clogged with iron, there goes your efficiency.

bob...

[crater]

just wanted to add my 2 cents in also jdoll, I haven't got my Geo all in yet but it is going to be 1- 300' well "Pump n' dump system", the idea is that the return water that is returned at the 300' depth will be moved away by the aquafur before it could be pumped back up. The submersible pump will be set at 150' at least 100' away from the return. Here in Iowa they have had some problems with the return water freezing the well in the winter, so they also dig a return pit and fill it with rock just in case the weather would stay cold for weeks on end. then at a predertrimened water temp a valve that automactically switches over to the pit would be turned on to avoid a freezing problem. Sounds like alot of crap that could potentially go bad or fail over time (High maintence) but for a $30ish heating bill I guess I can't complain. My system also costs about the same. mine is estimated to come in for $21K well and pumps included.

[Bill Arden]

the idea is that the return water that is returned at the 300' depth will be moved away by the aquafur before it could be pumped back up.

Here in MN it's illegal to pump water back down a well.

I've not heard of water freezing problems as most systems I've seen use a sloped drain pipe that drains when the system turns the water off.

The snow on the ground insulate the ground and keep it thawed out.

Anther problem is that removing deep water can cause problems since that will draw contaminants down into the aquifer.

So the consensus is that "Pump n' dump" systems should use shallow wells.

[boze62]

I will agree with some of the posts, geothermal units are high maintenance machinery. I have a well to well system (open loop) installed in 1992 in a new home construction. I was living in a 962 sq ft home with elctric baseboard heat averaging $125/month in cost (no A/C). Then I moved up to a 1500 sq ft home with heat and A/C and kept it slightly warmer, and my average that year was the same!

About $3000 extra cost for the system, $3500 to drill a 290 ft well to supply (used the old well as return well or likely would have been another $1500, it is a 120 ft well which handles the return flow). I know I am ahead of the game, but maybe only by a small margin after replacing the pump once, redoing the soleniod shut off and in home supply and a couple of other things. These guys are not cheap.

[crater]

Yea Bill I'm kind-of leary about pumping back down my well also, but it is not against the law here in IA, I know a couple a people that have the same system and love it, however they both pump back to surface (Pond,creek), I just talked to my HVAC guy, he said that this was the only year he has ever had a problem with the freezing of the well, the return water is around 6d colder going back down than suppied. anyway they have a sollution for it, the discharge pit (French Drain)
BTY I have heard some rummor's that the state DNR is going to be looking into the pump n' dump systems, so it probaly won't be long before the outlawed here also, especially since neighboring states have already have banished them.

[CWinAZ]

Greetings! I am new to this forum, my first post. I have a question and have been searching for an answer. I live in Metro Phoenix, AZ and want to install an open loop GSHP system using a cistern for water source and return. My home is a 2 story and currently has 2-3 ton air to air HP's. Reading from several sources I would need about 18 gpm of water. How many gallon capacity buried fiberglass cistern would I need? I plan to use the water to irrigate a small area in the back yard and collect water from the roof to add to the cistern when available. Not allowed to drill a well in the neighborhood and am on city water and sewer.

[bartman99]

just wanted to add my 2 cents in also jdoll, I haven't got my Geo all in yet but it is going to be 1- 300' well "Pump n' dump system", the idea is that the return water that is returned at the 300' depth will be moved away by the aquafur before it could be pumped back up. The submersible pump will be set at 150' at least 100' away from the return. Here in Iowa they have had some problems with the return water freezing the well in the winter, so they also dig a return pit and fill it with rock just in case the weather would stay cold for weeks on end. then at a predertrimened water temp a valve that automactically switches over to the pit would be turned on to avoid a freezing problem. Sounds like alot of crap that could potentially go bad or fail over time (High maintence) but for a $30ish heating bill I guess I can't complain. My system also costs about the same. mine is estimated to come in for $21K well and pumps included.

Hi Crater,

I just found your post. I was wondering how your system turned out? I am contemplating the same thing. We live in Virginia and have a 400' well (12gpm).

Does your well also supply potable drinking water? That is what we are contemplating too. Any specs on how the water temp in the well is affected by the heat pump return water? One fear is that the aquifer will not be able to handle the temps and will eventually reach a steady state with the HP (ie become too warm or too cold to be effective). Have you or any of your neighbors had a problem with this?

Thanks in advance,

BM

[Bill Arden]

Metro Phoenix, AZ ... open loop GSHP system using a cistern for water source and return.

Ouch.

It's not just the flow rate. you need to figure out how the water is going to be cooled back off again.

I would suggest you start with a closed loop drilled well system. to save costs you could start with cooling only using a water "A" coil or some other water to air radiator.

The closed loop wells last "almost" forever so in your case it is a good way to start.

Edit:
"almost forever" in this case is defined as the life expectancy of burred black plastic pipe.
I believe it's in the 100's of years so it can be considered a gift to future generations since heat pumps are likely to be used more and more in the future.

[statjunk]

Theoretical question. How far down would you have to dig a well so that when water is dropped down it will return as steam to power a turbine?

Couldn't you theoretically power a place for virtually free with a deep enough well?

Does this make any sense?

Tom

[speedbump]

That is a good question. I know you can do it in parts of Colorado.

bob...

[jadnashua]

Geothermal steam very much depends on where you live. In Iceland, they generate nearly all of their electricity that way, but then the island is essentially an old volcano. In some places, it is feasible, in others, it isn't, and unless very near the surface, unlikely to be useful on an individual level. Now, if you live near Yellowstone, maybe it would be fairly easy to tap a hot spring.

[Bill Arden]

Theoretical question. How far down would you have to dig a well so that when water is dropped down it will return as steam to power a turbine?

I believe it was 4 miles :eek:here in MN when I looked it up.

Drilling a 100 foot well costs $3000 so.... a deep enough well to create power would be way to expensive here.

Edit: I would be far better off investing in that company that wants to do "hot dry geothermal power" in Yellowstone.

[speedbump]

Not to mention when drilling that deep they start out very big at the top and scale down as they go. The deeper they go, the harder it is and the longer it takes. So by conventional standards, there would be no comparison to cost.

bob...

[statjunk]

I believe it was 4 miles :eek:here in MN when I looked it up.

Drilling a 100 foot well costs $3000 so.... a deep enough well to create power would be way to expensive here.

Edit: I would be far better off investing in that company that wants to do "hot dry geothermal power" in Yellowstone.


Jeeze-o-petes!

[barrybud]

Hello,

I've been reading through the thread and cant imagine dealing with the wells and the iron or other things that could foul up a system.
I'm in a story and 1/2 cape here in PA with a 4 season oil set up with water baseboards. I originally started looking for a Central A\C system because the summers here can be down right soggy with humidity. What I found was for about 35% more money I could get a direct exchange geothermal system to do both heat and AC over the cost of a central AC system.
This system doesn't use wells or water/antifreeze loops. I have 6 earth taps that are 70 feet deep in a conical shape that all join at the manifold. Two lines run inside the house to the air handler and the system uses R22 refrigerant. I only had an area about 10 feet around disturbed in the front yard with a small trench running to the house for the installation. It cost me a bit more because I had no air ducts run in the house before the geo system. The money I saved in the cost of the oil we would have used in the last 5 years has paid for the system. It also makes all the domestic hot water and the only time it kicks into 2nd stage is when the other half takes an extra long shower right when the heat comes on. The system gives priority to the hot water and the stat will kick in the electric element after 45 minutes if the house doesn't hit the set temp.

Here is a link for more info on the Geo company.
http://www.advancedgeotech.com/techov.html

[Bill Arden]

The "earth taps" are just another way of saying "Closed loop heat exchanger"

I've considered pounding in pipes and doing the same thing, except with water to transfer the heat to the Heat pump instead of running the freon into the ground loops.

Plastic is cheaper than copper and water is cheaper than freon.

On the other hand each person has to look at what works best in there area and the direct systems are better where the ground temps are close to the freezing point.

[sunny h]

I'd like to know what sort of water heater those of you with geo systems are using with your desuperheaters and buffer tanks? I know a heater is needed to bring the water up the last bit, and for shoulder times of year when the system is not running a lot.

[gator37]

I believe the correct term from ARI is "Closed Loop Ground Coupled Heat Pump" (CLGCHP) unless they have changed it.

Originally (1991 or so) there was a problem with the correct configeration of desuperheaters in the hot water heater storage tank. You may want to check some of the manufacturers such as Climate Master and see what they provide or recommend.

[Angelb]

What's a Thermal Well Cookie?

http://www.gas-lights.net/images/img6.gif

Thermal well is use to control water cooling and heating system

[gregs1]

Hello,

I've been reading through the thread and cant imagine dealing with the wells and the iron or other things that could foul up a system.
I'm in a story and 1/2 cape here in PA with a 4 season oil set up with water baseboards. I originally started looking for a Central A\C system because the summers here can be down right soggy with humidity. What I found was for about 35% more money I could get a direct exchange geothermal system to do both heat and AC over the cost of a central AC system.
This system doesn't use wells or water/antifreeze loops. I have 6 earth taps that are 70 feet deep in a conical shape that all join at the manifold. Two lines run inside the house to the air handler and the system uses R22 refrigerant. I only had an area about 10 feet around disturbed in the front yard with a small trench running to the house for the installation. It cost me a bit more because I had no air ducts run in the house before the geo system. The money I saved in the cost of the oil we would have used in the last 5 years has paid for the system. It also makes all the domestic hot water and the only time it kicks into 2nd stage is when the other half takes an extra long shower right when the heat comes on. The system gives priority to the hot water and the stat will kick in the electric element after 45 minutes if the house doesn't hit the set temp.

Here is a link for more info on the Geo company.
http://www.advancedgeotech.com/techov.html

I had thought about a geothermal system, probably the cheapest, is a rectangular hole. You dig down 6 feet maybe 12 by 24 foot trench. You just layer the bottom with plastic piping, and fill her up with dirt. Done. I'm sure the the location and terrain will determine the efficiency.

[GeoffBoyes]

Hey I also have a geothermal hot water system, and I need to advise everyone who gets one to watch the installation. It uses the surplus heat from the air conditioning freon, to heat water, which is circulated through the heat exchanger. the problem was that the installer simply hooked it up to an 80 gallon electric hot water unit. Well the crazy fact is that when I shower at 5:30, and pull down the hot water, the cold water entering the unit is quickly heated by the electric element to 130 degrees, and by the time the air conditioner starts operating at 12:00 am and the afternoon, to provide all that good free hot water, the water entering the exchanger is 130 degrees. So the unit says, sorry, thats as hot as I am alowed to heat water, go back to the electric hot water tank. SO,,, you get NO effective heating unless you are pulling water when the air conditioner is operating, and even then the electric elements will heat much faster than the heat pump. So I got an old 80 gallon hotwater tank and installed it as a "storage tank". The cold water enters this tank, there is no electric elements in it, The water constantly circulates until the whole tank reaches 130 degrees. Now when I take a shower, the electric hot water unit is replenished by 130 degree water from the storage tank. I am looking forward to seeing how much my electricity bill will drop, as I have only just completed this project, I am totally amazed that the manufacturer would not insist that the unit be installed with a holding tank, as the system I had was totally useless. Needless to say I cool the house for under $200, and my neighbors are running up $400 bills for the same size house. Its maintenance free, had it 3 years now. No noisy compressors outside, greatest thing since sliced bread.

[gdgraham]

I agree with your setup as that is how we generally install our units unless space or money is an issue. Here in Canada they work great in the winter even with one tank as the desuperheater will generate heat while the heat pump is heating your house all through the frigid night.

[gdgraham]

Quote - "I had thought about a geothermal system, probably the cheapest, is a rectangular hole. You dig down 6 feet maybe 12 by 24 foot trench. You just layer the bottom with plastic piping, and fill her up with dirt. Done. I'm sure the the location and terrain will determine the efficiency."

There are a lot of factors when designing a ground loop. Six feet is typically sufficient for depth but you will need a lot more area unless you live in a shoebox. Typical sizing for equipment in Ontario is 2 tons of capacity for 1000 square feet of house (not counting basement) you might add a size if you have an old house, walk-out basement, or an extraordinary number of windows, or a leaky house. Based on that you would want 600 ft of 3/4 pipe for each ton of equipment capacity. Each roll needs about a thousand sqaure feet of space. As an example a newish 2000 sq ft house might have a four ton heat pump. This would require four 600 ft rolls of pipe. You could lay this out in a 40 by 100 ft area or perhaps a couple 300 foot trenches that are at least two feet wide, or a four foot plus wide 600 foot race track, you get the idea. Basically you don't want to undersize or underspace your loop, especially for heating, or it will not be able to pull enough heat from the ground. Then your equipment will work too hard and eventually go poof. (Or at least repeatedly shut off if it has good self-protection controls built in.)

Cheers,
Geoff