Geothermal HVAC

GreenPowerManiacGreenPowerManiac Solar Expert Posts: 453 ✭✭✭
Anyone has one of these systems installed already ? Looking for data on subject.

Recently, I've contacted Jay Egg of EggGeothermal. Author of Geothermal HVAC book now published. Quickly I've been pointed to another fellow out of Minnesota who's trying to get me to invest in a system that seems either inadequate or makes no sense at all. For the most part, he's a salesman trying to sell me garbage that may/may not work.
For starters, wanted to dig two more wells than I've already got. One supply and other Return well. $8000 for that. Next is the design/management charges and lodging BS, $5000.
And to boot, not rhyming with Coot, charges for the geothermal heat pump, squirrel cage and coil about $5500. After research online, found out this unit cost $3300. Not to mention another $2000 for re-routing a few wires to make the heat pump work, which can do myself for under $100. Unbelievable trumped up charges for doing simple work. Calculated about $6500 for materials and my time to install and troubleshoot. Maybe another $1000. Compared to the earlier, $20500 rough bid, around $13000 after rebates/tax credits and about a year to take advantage of credits, my cost would be around $3750 after credits.

Here's a breakdown of the material list:

1) Geothermal Heat Pump Genesis series 3.5 ton 5.3 gallons per minute (GPM) $3352 EER 20.3 COP 4.0
2) 2 stage thermostat - 2 cooling/2 heating 60
3) Misc. parts and wiring done myself 300
4) HVAC install by outside service 600
5) Trench lines - done myself FREE
6) HDPE 1" return line to well (Standing column well method) use existing well 250
7) Whole house water filtration system 1000
8) Well cap modification from return line 500
9) Shipping and tax: 500
Total:
$ 6562 Rough estimate
Tax credits 30% -1969
State Rebates (For geo unit only) -1500
$ 3093

The real question is, does anyone have experience with heat pump setup and operations ?

Since I've been told, it's hard to get heat off an ice cube, I'm a bit skeptical even with the new technology of heat extraction from 50 degree water sources. Generally, there usually has to be a backup source of heat/cooling in case inclement weather arrives and lingers.
Nature's Design & Green Energy on FaceBook : Stop by and "Like" us anytime.. Many up-to-date articles about Renewables every day.
WWW.GreenAnything.Net    Ad free website.
Lots of DIY Renewable Energy Projects on ETSY : Solar Panel builds, Wind Turbine builds, Rain Barrel build,etc.  
«1

Comments

  • Blackcherry04Blackcherry04 Solar Expert Posts: 2,490 ✭✭✭
    Re: Geothermal HVAC

    I had water / air heat pumps ( 5 ) ones on a houseboat. Once the water got into the low 50 deg's it became iffy alone . The heat differential just wasn't there. I finally rigged up a hot water heater and a fluid system and coils to add supplemental heat to the air. I'd circulate 132 deg out and return it at 96 deg. It all seemed to work ok, it would re-heat during the off cycle. You have a lot of variables to look at.
  • inetdoginetdog Solar Expert Posts: 3,123 ✭✭✭✭
    Re: Geothermal HVAC
    The real question is, does anyone have experience with heat pump setup and operations ?

    Since I've been told, it's hard to get heat off an ice cube, I'm a bit skeptical even with the new technology of heat extraction from 50 degree water sources. Generally, there usually has to be a backup source of heat/cooling in case inclement weather arrives and lingers.

    Relative in MO has a custom geothermal system that uses coils submerged in the outlet of a natural spring. Water level ~50F year round. Great for AC in the summer and does not require use of resistance aux heat in the winter as long as you do not raise the thermostat too fast.

    Water source well below the frost line should work equally well.

    I am just uncomfortable with systems that use aquifer and pump water out and back. Too great a chance of contamination for me.
    SMA SB 3000, old BP panels.
  • GreenPowerManiacGreenPowerManiac Solar Expert Posts: 453 ✭✭✭
    Re: Geothermal HVAC

    Completely safe on pumping and (dumping) back to the same permeable source zone. In fact, with a whole house filter, would return it in better quality than started with little or no corrosion in the future. The moron tried to say it was OK to dump the well water into my 1/2 acre pond, which the health dept. would be all over like flies on sh*t. If you ever had a leaky garden hose, you'd notice the iron/sulfur/mineral scum it leaves behind, and when you water the garden with it, the veggies don't grow the same. Why would anyone want to destroy a natural habitat ?

    Right now, my well is at 140', capable of 180'. Water temp year round is between 47-50 degrees from the well. From what you're saying, 50 degrees is enough to sustain a comfortable temperature inside to heat the place without extra assistance from conventional means, right ?
    The difference between the older outside units and the new inside units is the outer one has to fight the elements of winter and go through a defrost cycle when the condenser frosts up, and must use another heating element or exchanger to assist while defrosting. Educated guess, that's why the newer ones work much better.
    I'm curious that this geothermal heat pump would cycle the same as conventional. Example: In summer, the cooling cycle runs on conventional, about 30 minutes out of each hour total on a hot day. Would the geosystem pump water, in this case 5.3 gpm for the total of 30 minutes ? (159 gph).
    Nature's Design & Green Energy on FaceBook : Stop by and "Like" us anytime.. Many up-to-date articles about Renewables every day.
    WWW.GreenAnything.Net    Ad free website.
    Lots of DIY Renewable Energy Projects on ETSY : Solar Panel builds, Wind Turbine builds, Rain Barrel build,etc.  
  • inetdoginetdog Solar Expert Posts: 3,123 ✭✭✭✭
    Re: Geothermal HVAC
    I'm curious that this geothermal heat pump would cycle the same as conventional. Example: In summer, the cooling cycle runs on conventional, about 30 minutes out of each hour total on a hot day. Would the geosystem pump water, in this case 5.3 gpm for the total of 30 minutes ? (159 gph).

    The one I am familiar with runs glycol in a cooling loop through the pond and then uses a water heat exchanger on the heat pump itself.
    Running coolant that far would be prohibitive. The loop pump is always on while the heat pump is running, regardless of the heat exchanger temperature.

    Even though the summer water temp is lower enough to provide some cooling all by itself, the heat pump runs its refrigerant cycle anyway and just does not have to work very hard.
    In your case, I cannot say what it is designed to do.
    SMA SB 3000, old BP panels.
  • Blackcherry04Blackcherry04 Solar Expert Posts: 2,490 ✭✭✭
    Re: Geothermal HVAC

    I would question that if you pulled the water from a well and re-injected it back into the same well how long you could expect the temperature of the water to remain at 50 deg. Your talking about a lot of water that will leave the heat exchanger at least 10-15 deg cooler in the winter and the reverse in the summer is even more. Seems like the well would absorb the heat and cold over time. It wasn't unusual to see ice on the heat exchangers on my boat in the winter. It's all about GPM and what you listed seems low.
    From what you're saying, 50 degrees is enough to sustain a comfortable temperature inside to heat the place without extra assistance from conventional means, right ?

    Thats where your comfort comes in. 72 deg air is warm, your body is 98 deg, 72 deg air blowing on you feels cold. Heat Pumps require a lot of design knowledge. The farther the ducts are from the heat exchanger, the cooler the air. You can have one register putting out 90 deg heat and another putting out 68 deg. The return air to the air handler is important also because of the exchange rate.

    Here is a forum that might answer some of your questions.

    http://www.geoexchange.org/forum/geothermal-heat-pump-discussions/

    .
  • GreenPowerManiacGreenPowerManiac Solar Expert Posts: 453 ✭✭✭
    Re: Geothermal HVAC

    Yes, I've wondered how fast it would heat things up inside the well. May greatly depend on the aquifers size and its ability to disperse the heat fast enough. As the water cools, it drops down toward the pump. 10-15 degrees may not be a big problem descending to 140'. Hard to say without testing the system. If the warm up is slow enough, then one would think the system would become gradually less efficient as the weeks went by until cooler weather arrives. Same effect at the start of winter and end, starts warmer from the summer build up and returns to 47-50 degrees eventually. What I don't quite get is why a system needs 5.3 gpm to heat an exchanger when radiant floor heating is done at the slowest gpm to allow heat transfer.
    Nature's Design & Green Energy on FaceBook : Stop by and "Like" us anytime.. Many up-to-date articles about Renewables every day.
    WWW.GreenAnything.Net    Ad free website.
    Lots of DIY Renewable Energy Projects on ETSY : Solar Panel builds, Wind Turbine builds, Rain Barrel build,etc.  
  • inetdoginetdog Solar Expert Posts: 3,123 ✭✭✭✭
    Re: Geothermal HVAC
    What I don't quite get is why a system needs 5.3 gpm to heat an exchanger when radiant floor heating is done at the slowest gpm to allow heat transfer.

    Here is an incomplete explanation:

    Radiant heat does not need to transfer a lot of heat in a short time. A heat pump, unless it can be throttled down as with an inverter driven compressor, will run at only one transfer rate and the outside loop has to move that much heat. This will let the heat pump be designed to cycle on and off instead of running continuously.

    Radiant heat also starts off with very hot water compared to the floor temperature, so the heat transfer can take place with a lower flow.
    The heat pump works best when working with small temperature differences, so the outside loop has to be very efficient to allow that.
    SMA SB 3000, old BP panels.
  • Blackcherry04Blackcherry04 Solar Expert Posts: 2,490 ✭✭✭
    Re: Geothermal HVAC

    Here is a explanation I found.
    In an open loop, standing column system, GSHPs take water out of the well and (assuming we’re heating the house for the sake of this demonstration) take the heat out of the water and dump back in freezing cold water into the well. So in this case you are starting to cool down your well water which also means the water you draw out gets colder and colder making the system less and less efficient. Therefore the more massive (or deep) the well is, the harder it will be for you change its temperature.

    Now, what if, instead of dumping that water back into the well, you dumped it “overboard” into a drywell? You could eliminate this well-cooling phenomena and keep your well at it’s optimum efficiency. This is called bleed. The more bleed you have, the greater the volume, OR recharge rate, your well needs to have. This is why, if you have lots of bleed your well doesn’t need to be as deep (though it does need to have good flow). In some parts of the country, especially near bodies of water or high population areas, the amount of bleed you are allowed is limited.

    Rules of thumb for well depth: Open Loop
    55-ft. depth per ton at 30% bleed
    85-ft. depth per ton at 10% bleed
    150-ft. depth per ton at 5% bleed or less


  • techntrektechntrek Solar Expert Posts: 1,372 ✭✭✭
    Re: Geothermal HVAC

    I drooled over GSHP systems for years, even talked a friend of mine into installing one when he built a new house. What prevented me from doing it was the price.

    Then a few years ago along came the ultra-efficient mini-splits talked about often here. Compare the SEER/EER/COP of GSHP systems to the mini-splits (highest SEER I've seen is 28) and the mini-splits come out way ahead in efficiency and lower cost.

    I no longer want a GSHP.
    4.5 kw APC UPS powered by a Prius, 12 kw Generac, Honda EU3000is
  • Blackcherry04Blackcherry04 Solar Expert Posts: 2,490 ✭✭✭
    Re: Geothermal HVAC

    I once had a set of plans where you built a tank under the garage floor when you poured the basement. It held about 35,000 gallons of water. The concept was that it heated in the summer and you used the heat in the winter. Heat Pumps were new at the time in the mainstream and I got scared the tank would crack or leak, In the end I didn't do it. Another time I buried 5 , 1,000 gal. concrete septic tanks and gave that a whirl, that ended up being a boondoggle with the water either to hot or to cold at the wrong time of year and to little volume.
  • NorthGuyNorthGuy Solar Expert Posts: 1,913 ✭✭
    Re: Geothermal HVAC
    I once had a set of plans where you built a tank under the garage floor when you poured the basement. It held about 35,000 gallons of water. The concept was that it heated in the summer and you used the heat in the winter. Heat Pumps were new at the time in the mainstream and I got scared the tank would crack or leak, In the end I didn't do it. Another time I buried 5 , 1,000 gal. concrete septic tanks and gave that a whirl, that ended up being a boondoggle with the water either to hot or to cold at the wrong time of year and to little volume.

    There's a village close to Calgary, which uses this principle to cover all their heating needs. It was very expensive to build and the heat storage is gigantic. They have a Web site. I can't find it :grr
  • Blackcherry04Blackcherry04 Solar Expert Posts: 2,490 ✭✭✭
    Re: Geothermal HVAC
    NorthGuy wrote: »
    There's a village close to Calgary, which uses this principle to cover all their heating needs. It was very expensive to build and the heat storage is gigantic. They have a Web site. I can't find it :grr
    I know it can be done, the problem is that the Refrigerant cycle has specific needs. You only get the correct pressure with the right temperatures otherwise the savings are just not there, they need correct flow and transfer of heat/cold. I only have one in the boat I have now, it's 6,500 BTU heat pump in the master br. It has a 200 gph water pump that runs wide open through a tube in tube heat exchanger. It's sweet spot is from about 55 deg to 80 deg water, it will still work out of that range, but you feel the drop off in the output temperatures.
  • GreenPowerManiacGreenPowerManiac Solar Expert Posts: 453 ✭✭✭
    Re: Geothermal HVAC

    So how far away from the original well does the "Bleed" well need to be to ensure optimum performance ?
    Nature's Design & Green Energy on FaceBook : Stop by and "Like" us anytime.. Many up-to-date articles about Renewables every day.
    WWW.GreenAnything.Net    Ad free website.
    Lots of DIY Renewable Energy Projects on ETSY : Solar Panel builds, Wind Turbine builds, Rain Barrel build,etc.  
  • inetdoginetdog Solar Expert Posts: 3,123 ✭✭✭✭
    Re: Geothermal HVAC
    So how far away from the original well does the "Bleed" well need to be to ensure optimum performance ?

    Depends entirely on the volume being pumped, the nature of the aquifer in terms of recharge rate, depth of layer, etc., and whether the bleed well returns water to the same aquifer as the source or not.

    If you know all of the variables, you can plug into a formula, but there is no one answer.

    Like any use of underground water, if your use combined with all other uses exceeds the replenishment rate of the aquifer, you will cause problems.
    SMA SB 3000, old BP panels.
  • Blackcherry04Blackcherry04 Solar Expert Posts: 2,490 ✭✭✭
    Re: Geothermal HVAC
    So how far away from the original well does the "Bleed" well need to be to ensure optimum performance ?
    I have no clue. In florida my parents home had one well in the front yard and one in the back. So maybe they were 75 feet apart. There the water table is real high and the well was only 25-30 deep and hand washed into the ground. They just took out of one well and dumped the discharge back into the other, so there was no bleed.

    Here is the web site I got that info from, dig around you might find something. I have enjoyed looking for you, don't have the answers you seek.

    http://www.greenbuildingadvisor.com/blogs/dept/green-architects-lounge/ground-source-heat-pumps-part-2-rules-thumb
  • solarvicsolarvic Solar Expert Posts: 1,060 ✭✭✭✭
    Re: Geothermal HVAC

    I was thinking og a gshp a few years ago. My friend that installs them told me if your water has a lot of minerals that the heatpumps life is short. I think the slinky method is the best as long as you have the space. Dont shortcut the amount of pipe and depth you bury it. For my area in northwest pa. I would have 800 ft of pipe per ton and bury it 6 ft. That way you can use your filtered water and antifreeze and never have to worry. If you look on youtube you can find how to build a slinky. :Dsolarvic:D
  • Blackcherry04Blackcherry04 Solar Expert Posts: 2,490 ✭✭✭
    Re: Geothermal HVAC
    So how far away from the original well does the "Bleed" well need to be to ensure optimum performance ?
    Here is some more theory about two wells.
    The disposal methods preferred by the National Ground Water Association, from a water conservation standpoint, are secondary use of the water and returning the water to the production aquifer.

    When returning the water to the original aquifer, the water should remain in a closed system. There are several methods for returning the water to its aquifer. They are: using a single well for supply and disposal; using two wells and alternating withdrawal and disposal between the wells in winter and summer; and using two wells, but not alternating their function.

    Single well — For return of water in a supply well, approximately 100 feet of vertical separation is required for every 12,000 Btu of heating or cooling produced per hour. A typical domestic geothermal heat pump, with a 60,000 Btu capacity, would require 500 feet of separation in the well from the point of disposal to the point of supply. If 1000 feet of vertical separation were needed, it probably would be inadvisable to use this system. Higher drilling and pumping costs could make this system impractical in many areas. Also, local regulations may restrict the use of a single well for both potable water and return.

    Two-well system (alternating) — This method could take advantage of any temperature variations that may exist in the ground water from this process. In winter, a return well injects cooler water back into the aquifer. summer, the return well (now acting as a supply well) could withdraw this cooler water from the aquifer for more efficient cooling. The second well could be used in a similar way for warmer water. Alternating supply and return may also be beneficial as a preventive maintenance measure. The alteration in each well helps prevent clogging of the well screen, a common problem. This method of design is rarely practiced, probably due to its larger initial investment. The system would require an additional pump (one per well) and more piping compared to other systems.

    Two-well system (nonalternating) — A general rule to follow is to drill the return well to the same aquifer at the same depth as the producing well. Return wells in sand and gravel aquifers must have a screen to help prevent incrustation and facilitate water movement. Water is always returned below the water level to reduce precipitation of dissolved solids on the well casing.

    If a return well is drilled, it must be placed far enough from the supply well to prevent an overlapping thermal effect between the two wells. Raphael G. Kazman in his report, Use of Twin Wells and Water-Source Geothermal Units for Energy Conservation in Louisiana, created a table for use by the project engineer or designer to approximate the needed spacing between the production and return wells. These wells alternate their roles: the well used for production in the summer is used for return in the winter and vice versa.

    Kazman reported that if each house in an entire housing development were equipped with twin wells and geothermal heat pumps, the return water of one property owner might be pumped by his neighbor. The studies he conducted indicate that to maintain the same well discharges without danger of interference with neighbors, the spacing between the twin wells must be increased, possibly as much as 20 percent or more. To minimize interference and short-circuiting between neighboring sets of twin wells, the summer well should always be located on the street side of any lot, and the winter well should be drilled in the backyard, he says.

    Two wells, even in the same aquifer, keep the temperature difference separate, if properly spaced, because underground water flows so slowly. The spacing of the supply and return wells is dependent upon several variables, among which are:

    selection of the optimum geothermal heat pump based on available well capacity and operating cost
    the length of the critical season of operation (overall duration of the heating season in the North, air-conditioning season in the south)
    the actual number of days that the GeoExchange unit will be called upon to operate and the percentage of time during those days that it will actually be in operation
    the aquifer characteristics: permeability, thickness, and specific capacity.

    Spacing the supply and return wells at least 100 feet apart are best for most locations. For good aquifer conditions, this spacing might be less, while greater spacing may be necessary for poor aquifer conditions. The return well has to be constructed as well as, or better than, the supply well–it is not just a dumping hole.

    Theoretically, an aquifer will accept the same amount of water that it will yield. In reality, however, it will only accept 75 to 80 percent of its yield in return. Therefore, an aquifer that will yield 18 gpm will only accept approximately 14 gpm and the remaining 4 gpm will run out on the ground. The contractor and homeowner should be concerned about the possible plugging of the return well by deposits of sand or high amounts of iron being present in the ground water. Air dissolved in the water can also induce corrosion.

    It should be noted that in aquifers with low permeability, gravity feeding of return water might not provide sufficient pressure to allow infiltration into the aquifer. If the discharge water is returned to an aquifer other than the supply aquifer, and the two aquifers are separated by a thickness of low-permeability material, interference should be minimal or nonexistent.

    Supply and return aquifers must be chemically compatible to assure that mixing of the two water types does not result in precipitation of salts or hydroxides from solution, which might lead to eventual plugging of the aquifer surrounding the return well.
  • GreenPowerManiacGreenPowerManiac Solar Expert Posts: 453 ✭✭✭
    Re: Geothermal HVAC

    That's Neat ! Where did you get this article ?

    Also signed up in the GeoExchange forum. So far, got a bunch of techno geeks all saying different things. Very confusing.
    Nature's Design & Green Energy on FaceBook : Stop by and "Like" us anytime.. Many up-to-date articles about Renewables every day.
    WWW.GreenAnything.Net    Ad free website.
    Lots of DIY Renewable Energy Projects on ETSY : Solar Panel builds, Wind Turbine builds, Rain Barrel build,etc.  
  • Blackcherry04Blackcherry04 Solar Expert Posts: 2,490 ✭✭✭
    Re: Geothermal HVAC
    That's Neat ! Where did you get this article ?

    Also signed up in the GeoExchange forum. So far, got a bunch of techno geeks all saying different things. Very confusing.
    It came from here. I was really surprised how much Geothermal heat Pump info is out there.

    http://wellowner.org/geothermal-heat-pumps/q-what-do-i-do-with-the-ground-water-in-an-open-loop-system-after-the-geothermal-heat-pump-has-used-it/
  • RandomJoeRandomJoe Solar Expert Posts: 472 ✭✭✭
    Re: Geothermal HVAC

    Interesting. I've worked on a lot of geo jobs, but never seen an open loop one. They were all closed-loop, with a down-and-back loop of pipe in each well. Of course I only work on commercial buildings, so much larger scale. Might have 20-30 wells each 200-400 feet deep (depending on water table level) spread across the grounds around the building.

    The systems seem to work well enough most of the time, but I've been to several buildings that apparently had little or no ground water around the well field. Under light load conditions things would be okay but with a heavy load the ground would heat up fairly quickly and the return water from the well field would climb dangerously high. (We're almost always in cooling mode. Even in a cold winter, there's usually enough heat load to keep many / most units cooling.)

    These are mostly in schools. They get federal grant money for installing the things. Doubt they'd do it otherwise, drilling the well fields is remarkably expensive.

    One of the indian tribes tried using ponds for their cooling loop. Couldn't reject enough heat - had a nice warm pond though! They put a fountain in the pond, which helped - but still not enough. It also introduced another problem, they had to FILL the pond continuously thanks to evaporation. In the end we put standard cooling towers on the building to get the required cooling capacity. That building didn't need any heat either - a casino. All those gaming machines were one heckuva heat load, let alone the people in it.
  • northernernortherner Solar Expert Posts: 492 ✭✭✭✭✭✭
    Re: Geothermal HVAC
    NorthGuy wrote: »
    There's a village close to Calgary, which uses this principle to cover all their heating needs. It was very expensive to build and the heat storage is gigantic. They have a Web site. I can't find it :grr

    That would be the Drake Landing Solar Community in Okotoks, Alberta. They use 144 bore holes that transfer the heat collected in summer, down about 100 feet to a large volume of earth. This system supplies about 90 percent of the heat in winter to 52 homes in the community. This system was built as a pilot project between government and industry, to demonstrate the feasibility, and as you mention was very expensive to build.

    http://www.dlsc.ca/
  • SkippySkippy Solar Expert Posts: 308 ✭✭
    Re: Geothermal HVAC
    Anyone has one of these systems installed already ? Looking for data on subject.


    The real question is, does anyone have experience with heat pump setup and operations ?

    Since I've been told, it's hard to get heat off an ice cube, I'm a bit skeptical even with the new technology of heat extraction from 50 degree water sources. Generally, there usually has to be a backup source of heat/cooling in case inclement weather arrives and lingers.

    I happen to come across this older thread, so I don't know if you are still looking for info.

    I know from my monitor on my solar water heater, that the water temp coming into the house is around 45 degrees year round, and my heat pump pipes are buried about the same depth as my water supply line.

    When my "guy" installed my heat pump, he described systems that were installed in the small front yards of duplexes in Toronto . . . he had to take a jack-hammer to it to get to the lines, it was solid ice. these were closed loop - plastic pipe installs by someone who did not know what they were doing. . .

    After getting a few names from my "guy" I started digging into the geo thermal issue, and found a few unhappy people out there - all from one local company - that I won't name. Turns out that in my area, you need to have at least 600 feet of tubing - per ton of heat pump. 3 of the not so happy customers that I talked to had alot less than that - one person I know - has 7 tons of heat pump on a 700 foot loop, and every year, his yard collapses into a series of 24 inch deep trenches - right where the tubing is buried. . . seems the system is drawing all the heat out of the surrounding soil - solid ice - then come spring, it melts, turns too mud, and sinks, he says that he has filled those darn trenches 3 times in three years, and they keep coming back. . .

    When my system was installed, my "guy" brought an extra 600 foot roll of tubing, and when he found out the ground was dry sandy gravel, he asked me if I wanted to install the extra roll... which I agreed to, so I have 2,400 feet of tubing on a 3 ton - water furnace heat pump. . . installed about 6 or 7 feet down . . in dry sandy gravel. It works great ! . .. I keep the house at around 75 degrees year round, and do not use the a/c in the summer time . . . so I do not pump any heat back out either ( all natural recharge). I do notice that the heat pump heats the water up faster in the fall (ground is warmer - more available latent heat) than it does in the spring ( ground is colder - less available latent heat)

    As for taking the heat out of water, I asked if I could put a skating rink in my back yard, and have a set of ball valves divert the underground loop into a "rink loop", and he told me that it was possible to have an outdoor skating rink, (with a plastic loop) as long as the heat pump was drawing the heat out of the liquid (heating the house) . . now that would be cool . . no pun intended...

    Hope that helps.
    2 - 255W + 4 - 285W PV - Tristar 45 MPPT CC / 3 - 110W PV -wired for 36V- 24V Sunsaver MPPT CC / midnite bat. monitor.
    1 KW PSW inverter 24V / 2.5 KW MSW inverter-24V ~ 105 AHR battery.
    3 ton GSHP.- 100 gallon warm water storage / house heat - radiant floor / rad
    9 -220W PV - net meter - Enphase inverters and internet reporting system.
    420 Gallon rain water system for laundry.***  6" Rocket Mass Heater with 10' bed for workshop heat.
    Current project is drawing up plans for a below grade Hobbit / underground home.
  • fixitmanarizonafixitmanarizona Registered Users Posts: 4
    Re: Geothermal HVAC

    Try checking out the "Rocket Mass Heater" at permies.com. Uses VERY little wood, NO oil, gas, or electricity, and is much more efficient than any other heat source. Thing is, you have to build it yourself (as anything should be if possible,) you won't be finding any contractor to install this, nor will you be buying one to install yourself.
    It also puts out NO smoke, nor does it heat the outside air at all. All the heat is extracted into the thermal mass. The rocket burn chamber reburns all the smoke, extracting even more heat, and rendering no toxic fumes nor smoke. There is no chance of a chimney fire since there is no chimney. EVERY burn, burns completely.
    This is new (1990's) low-tech technology, and is still being improved. It's great because you can avoid buying anything, including fuel, from large companies or overseas sources.
    Just a thought.
  • Ken MarshKen Marsh Solar Expert Posts: 114 ✭✭✭✭
    Re: Geothermal HVAC

    Yes, there are hundreds of thousands of heat pumps out there.
    Success depends on design and application to your local conditions.
    I have personally made some 100 installations and did the engineering work for another 100.

    There are three distinct residential types.
    1. Air source
    2. water source closed loop
    3. water source open loop
    Each one needs different design parameters. The forgoing discussion thread tends to mix the types.
    Air sourced units are not recommended for the northern climates.
    The majority of the units going in today are type 2.
    I never installed a closed loop because of their high cost and lower efficiency.

    Here are a few thoughts that may help:

    Success depends upon your aquifer.
    If you have water in sand and gravel most all the way down you are good.
    Stay as shallow as you can with the wells even though the shallower water is colder.
    In general temperature goes up one deg F for each 50 ft you go down.
    Mineralization can be an issue. In general the deeper water is more mineralized.
    If you have over 500 PPM CaCO4 equivalent better get the scaling factor tested.
    Do not use filters. They will be a first class pain.
    4.5 gpm is too low flow for your temperature water and 3.5 Ton.
    Aim for more like 8 gpm which will fit the flow of standard submerged pumps.
    The larger flow with lower delta temp will have decidedly less tendency to scale
    and significantly increase capacity and efficiency.

    As for influencing the aquifer temperature, it us usually no problem.
    Space your return a couple hundred feet at least.
    Underground water moves. The movement is generally down hill.
    It will be moving the same direction the rivers in the area go.
    Put your source well up stream.

    I have used drilled return wells but in general do not recommend them.
    It is better to use a stream, pond, drainage ditch or even a dry well to return water.
    Drilled return wells have a tendency to plug in time.
    Some people recommend putting a pump in the return well so it can be flushed.
    But in general this does not work and adds considerable to the cost.

    Do not use a pond or stream for source water.
    They get very close to freezing in the winter.
    I know there are people out there using copper loops in their pond and claim it works great but...

    If you want long off cycles, geothermal is not for you.
    They have to run a lot.
    They are usually sized to run 100% at your coldest night.

    We just completed 35 years on our open loop heat pump.
    It provided all heat, cool and DHW for our family with no back up.
    It is home built since you could not buy them back then.
    It has been in four different houses.
    Each time we moved we took it with us.
    Two years ago I put a 3P compressor in it and run it with a VFD.
    That way I can run it with the Solar system.
  • GreenPowerManiacGreenPowerManiac Solar Expert Posts: 453 ✭✭✭
    Re: Geothermal HVAC

    Ken,
    Please PM me on the subject. Got some different designs to go over.

    Since the last post a few months ago, this is what's going on:

    Decided to go horizontal loop field, linear lines about 400' per ton with 3/4" HDPE (Pex) . I have a backhoe and will trench all the work to the house. That alone saves me $20k minimum.
    In and out lines are 1-1/4" about 150' each coupled up to the 3/4" loop field. Looking at about 3000' linear feet of field.
    Latest quote was for 6 ton, yet others have said 4 ton Synergy 3D.
    Did a Manual J assessment: Heating side says 50250 BTUs.
    Already have Solar PV and Water Heating/with/radiant floor. Integration from a hot water generator(included in the Synergy unit) would be a snap to utilize the 280 gallons of buffer tanks.
    No one has yet gave a credible answer to the "Sizing" riddle yet based on my info.
    Could anyone else solve this riddle from data given, and/or what info is actually needed ??
    Nature's Design & Green Energy on FaceBook : Stop by and "Like" us anytime.. Many up-to-date articles about Renewables every day.
    WWW.GreenAnything.Net    Ad free website.
    Lots of DIY Renewable Energy Projects on ETSY : Solar Panel builds, Wind Turbine builds, Rain Barrel build,etc.  
  • LucManLucMan Solar Expert Posts: 223 ✭✭✭
    Re: Geothermal HVAC
    Ken,
    Please PM me on the subject. Got some different designs to go over.

    Since the last post a few months ago, this is what's going on:

    Decided to go horizontal loop field, linear lines about 400' per ton with 3/4" HDPE (Pex) . I have a backhoe and will trench all the work to the house. That alone saves me $20k minimum.
    In and out lines are 1-1/4" about 150' each coupled up to the 3/4" loop field. Looking at about 3000' linear feet of field.
    Latest quote was for 6 ton, yet others have said 4 ton Synergy 3D.
    Did a Manual J assessment: Heating side says 50250 BTUs.
    Already have Solar PV and Water Heating/with/radiant floor. Integration from a hot water generator(included in the Synergy unit) would be a snap to utilize the 280 gallons of buffer tanks.
    No one has yet gave a credible answer to the "Sizing" riddle yet based on my info.
    Could anyone else solve this riddle from data given, and/or what info is actually needed ??

    The manual J calculations give you the capacity required for your home at the lowest temperature for your geographic area, use that number. Now to calculate the the size of the equipment required you have to remember that your system loop temp will drop as the winter progresses. The GEO will be removing heat from the ground and it will not be replaced as quickly as the system requires unless your loop is in the water table. In Feb. you can expect to see your loop temp to be 20-30 degrees or more colder than when the heating season started.
    No one ever talks about this, but it is fact on GEO systems.
    So to select the size of your equipment you will now have to select at a ground temp of approximately 30 degrees or less. Doing this you will see that the size of the equipment required is greater than at the 55 degree ground temp.
    The COP rating also drops substantially at the lower temp.
    A work around is to use 600' per ton on your loop field.
  • solarvicsolarvic Solar Expert Posts: 1,060 ✭✭✭✭
    Re: Geothermal HVAC

    Green power, After reading your post I have a couple suguestions I learned while researching on doing A geo system. Pennsylvania suggests for northern Pennsylvania.a 600 feet slinky of 1 inch tubing per ton buried at least 6 feet deep. I inch tubing tranferrs lots more heat and requires less electric for pumping because of a lot less friction than the 3/4 inch tubing you proposed.solarvic
  • GreenPowerManiacGreenPowerManiac Solar Expert Posts: 453 ✭✭✭
    Re: Geothermal HVAC

    http://www.pacificpumpandpower.com/docs/Friction_Loss_Table.pdf

    Since the last post, I've found this interesting Friction loss table for the loop field. Thinking now I'll just be going with 1.25" throughout to save on pump size and head pressure losses. 3000' lineal feet loop. And Yes, it will be in the water table as it's very high here, even in drought. Could dig 8' to make sure everything is in saturated soils. My 1/2 acre pond is down about 7' from full, and when digging the trench for my chicken coop geo project, the water was seeping in around 7'. This is at its lowest point for several years. In Spring, it's near or at ground level. The reason why my home is built 6' out of the ground yet surrounded by earth and/or 7' of front porch (7' of river sand separated between footings and covered by cement).

    Still not sure on what's meant about sizing the unit. Is the heat gain/loss number (50250) the lowest BTU number required to heat in the dead of winter ??
    My LP furnace is rated at 90k btus.
    First, need to know what size is required before determining loop field length. Area, I've got. HDPE I can get extra.

    With a slinky loop field, I've read the heat transfer isn't as great due to the lines overlapping each other. The bottom of tube pulls colder fluid faster and warmer transfers on top. More surface area for transfer at 1.25" and much slower flow helps on pump pressure and transfer like radiant floors.
    Nature's Design & Green Energy on FaceBook : Stop by and "Like" us anytime.. Many up-to-date articles about Renewables every day.
    WWW.GreenAnything.Net    Ad free website.
    Lots of DIY Renewable Energy Projects on ETSY : Solar Panel builds, Wind Turbine builds, Rain Barrel build,etc.  
  • LucManLucMan Solar Expert Posts: 223 ✭✭✭
    Re: Geothermal HVAC
    http://www.pacificpumpandpower.com/docs/Friction_Loss_Table.pdf

    Since the last post, I've found this interesting Friction loss table for the loop field. Thinking now I'll just be going with 1.25" throughout to save on pump size and head pressure losses. 3000' lineal feet loop. And Yes, it will be in the water table as it's very high here, even in drought. Could dig 8' to make sure everything is in saturated soils. My 1/2 acre pond is down about 7' from full, and when digging the trench for my chicken coop geo project, the water was seeping in around 7'. This is at its lowest point for several years. In Spring, it's near or at ground level. The reason why my home is built 6' out of the ground yet surrounded by earth and/or 7' of front porch (7' of river sand separated between footings and covered by cement).

    Still not sure on what's meant about sizing the unit. Is the heat gain/loss number (50250) the lowest BTU number required to heat in the dead of winter ??
    My LP furnace is rated at 90k btus.
    First, need to know what size is required before determining loop field length. Area, I've got. HDPE I can get extra.

    With a slinky loop field, I've read the heat transfer isn't as great due to the lines overlapping each other. The bottom of tube pulls colder fluid faster and warmer transfers on top. More surface area for transfer at 1.25" and much slower flow helps on pump pressure and transfer like radiant floors.

    Heat gain is the cooling load.
    Heat loss is the heating load calculated for the coldest day of the year for your area based on your insulation levels, exposed walls, roof, windows , doors etc.(50,250 BTU) as per your manual J calculations.
    Ground loop heat pumps are always selected for the heating load.
    90K btu input LP gives you 70,200 BTU's output with a standard 78% eff. furnace. Then subtract your duct loss if ducts are in an uninsulated area.
  • GreenPowerManiacGreenPowerManiac Solar Expert Posts: 453 ✭✭✭
    Re: Geothermal HVAC

    Furnace is 93% efficient. 83700 btus output. Duct work are not insulated in basement (about 53 lineal feet) 1x2 rectangular. Same with return lines in basement.

    So which Synergy unit best matches up with the data ? : http://www.waterfurnace.com/literature/synergy3d/SC1300YS.pdf Any of them ?
    3000' feet @ 8' down through 1.25" pipe throughout. Approx 195 gallons total. 10-20 gallons per minute.
    Nature's Design & Green Energy on FaceBook : Stop by and "Like" us anytime.. Many up-to-date articles about Renewables every day.
    WWW.GreenAnything.Net    Ad free website.
    Lots of DIY Renewable Energy Projects on ETSY : Solar Panel builds, Wind Turbine builds, Rain Barrel build,etc.  
Sign In or Register to comment.