Geothermal heat pump

Discussion in 'Solar and Geothermal Water Heating Forum' started by Cookie, Feb 12, 2008.

  1. Cookie

    Cookie .

    Messages:
    5,658
    Location:
    .
    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.
    Last edited: Feb 14, 2008
  2. speedbump

    speedbump Previous member

    Messages:
    4,540
    Location:
    Riverview, Fl.
    What's a Thermal Well Cookie?
  3. Bill Arden

    Bill Arden Computer Programmer

    Messages:
    584
    Location:
    MN, USA
    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.
  4. Cookie

    Cookie .

    Messages:
    5,658
    Location:
    .
    Last edited: Feb 13, 2008
  5. hj

    hj Moderator & Master Plumber Staff Member

    Messages:
    26,631
    Location:
    Cave Creek, Arizona
    well

    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.
  6. speedbump

    speedbump Previous member

    Messages:
    4,540
    Location:
    Riverview, Fl.
    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...
  7. Rancher

    Rancher Guest

    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
  8. speedbump

    speedbump Previous member

    Messages:
    4,540
    Location:
    Riverview, Fl.
    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...
  9. Rancher

    Rancher Guest

    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
  10. speedbump

    speedbump Previous member

    Messages:
    4,540
    Location:
    Riverview, Fl.
    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...
  11. Rancher

    Rancher Guest

    Only if you stay out in the sunlight without sunscreen on, it gets to over 120 in the summer in Phoenix in the summer.

    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 agree, I can get my solar tank up to over 180 degrees in summer, those are glass faced solar panels.

    Rancher
  12. Bill Arden

    Bill Arden Computer Programmer

    Messages:
    584
    Location:
    MN, USA
    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
    Last edited by a moderator: Feb 15, 2008
  13. speedbump

    speedbump Previous member

    Messages:
    4,540
    Location:
    Riverview, Fl.
    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...
  14. alternety

    alternety Like an engineer

    Messages:
    651
    Location:
    Washington
    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.
  15. jdoll42

    jdoll42 Computer Systems Engineer

    Messages:
    68
    Location:
    In Illinois near St. Louis, MO
    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!
  16. speedbump

    speedbump Previous member

    Messages:
    4,540
    Location:
    Riverview, Fl.
    What was the initial cost for the entire setup including the wells?

    bob...
  17. jdoll42

    jdoll42 Computer Systems Engineer

    Messages:
    68
    Location:
    In Illinois near St. Louis, MO
    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.
  18. speedbump

    speedbump Previous member

    Messages:
    4,540
    Location:
    Riverview, Fl.
    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...
  19. jdoll42

    jdoll42 Computer Systems Engineer

    Messages:
    68
    Location:
    In Illinois near St. Louis, MO
    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.
  20. speedbump

    speedbump Previous member

    Messages:
    4,540
    Location:
    Riverview, Fl.
    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...
Similar Threads: Geothermal heat
Forum Title Date
Solar and Geothermal Water Heating Forum Is a heat pump neccessary for closed loop geothermal installation? Oct 23, 2011
Solar and Geothermal Water Heating Forum geothermal saltwater source Aug 8, 2013
Solar and Geothermal Water Heating Forum Can I add solar power to my existing Geothermal closed loop system? Dec 16, 2012
Solar and Geothermal Water Heating Forum Geothermal 30% Tax Credit Question Jul 5, 2012
Solar and Geothermal Water Heating Forum Geothermal System Keeps shutting OFF Feb 25, 2012

Share This Page