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  1. #1
    Join Date
    Jun 2008
    Posts
    5

    Air v Ground Source HP

    I apologize if this issue has been flogged to death somewhere else on this site but I could not find it. Closest I could come is the comparison between propane and geothermal.

    My question - I need to replace an old air HP and am trying to decide whether the 10- 20k additional upfront cost for geothermal is going to make sense. From what I can tell it comes down to efficiency between the two types of systems. Electricity rates sky rocketed here in Maryland last year so either way I'm going to come out better with a new unit of either kind. However, if electricity rates continue to climb, the system with the better efficiency will keep the bill lower and heating and cooling should really be no different unless I add a desuperheater to offset hot water costs some. Problem is, I cannot find an apples to apples comparison of air HP v geothermal HP to see if the differences in efficiencies are large enough to justify paying that much more.

    I also have not seen anything telling me how long a new air system would last relative to a geothermal system. People have posted numbers all over the map. Some firm figures would be greatly appreciated.

  2. #2
    Join Date
    Nov 2000
    Location
    Eastern PA
    Posts
    68,981
    I am an HVAC wholesale rep who sells HVAC products to HVAC contractors. I have seen a tremendous increase in geothermal systems being installed in Maryland, Deleware, New Jersey and Pennsylvania. So, I must assume that the benefits are outweighing the initial cost factor.
    Government is a disease...
    ...masquerading as its own cure…
    Ecclesiastes 10:2 NIV


  3. #3
    Join Date
    Nov 2007
    Posts
    86
    While it is true that a GSHP will be much more expensive up front, it is also true that if you do a life cycle analysis that you come out ahead with the GSHP. GSHPs have higher efficiencies resulting in lower operating costs. That and lower maintenance costs coupled with the proven record of GSHPs lasting much longer will result a much lower total cost when you do your calculations for the next 15 ~ 20 years.

    So the choice is entirely yours, would you like to replace the air-source heat pump you’ll install today in about 15 years at tomorrow’s prices because by then it will likely look like (and be as useful as) the Kursk, or would you like to install something that will have a useful life of 20 ~ 30 years while operating at an efficiency of perhaps 40% better than an air-source HP?

    I know this is rather anecdotal, but I know of no one who has installed a GSHP and is regretful; in fact most people are down right thankful, given where energy prices have gone. I’ve also been on a conference call to someone who installed a GSHP in the early 1950’s - and it’s still running - on the original compressor – a DX system no less!

    SR

  4. #4
    Join Date
    May 2008
    Location
    North Carolina
    Posts
    6
    Quote Originally Posted by jmueller View Post
    I apologize if this issue has been flogged to death somewhere else on this site but I could not find it. Closest I could come is the comparison between propane and geothermal.

    My question - I need to replace an old air HP and am trying to decide whether the 10- 20k additional upfront cost for geothermal is going to make sense. From what I can tell it comes down to efficiency between the two types of systems. Electricity rates sky rocketed here in Maryland last year so either way I'm going to come out better with a new unit of either kind. However, if electricity rates continue to climb, the system with the better efficiency will keep the bill lower and heating and cooling should really be no different unless I add a desuperheater to offset hot water costs some. Problem is, I cannot find an apples to apples comparison of air HP v geothermal HP to see if the differences in efficiencies are large enough to justify paying that much more.

    I also have not seen anything telling me how long a new air system would last relative to a geothermal system. People have posted numbers all over the map. Some firm figures would be greatly appreciated.
    Have you looked at the "Acadia" low temperature heat pump from Hallowell International? According to the specs, it's extremely efficient.

  5. #5
    Join Date
    Aug 2006
    Location
    Dallas (Plano), TX
    Posts
    168
    Quote Originally Posted by fsq4cw View Post
    ... I know this is rather anecdotal, but I know of no one who has installed a GSHP and is regretful; in fact most people are down right thankful, given where energy prices have gone ...
    I'm one of the people you refer to. I'm coming up on one year having a GSHP system for my 3400 sf, single story, not-so-well-insulated and leaky-window residence, in the current intense heat of Dallas, Texas, and I've concluded that a GSHP is 'the real deal.'

    Here in Dallas we're well into the 100+°F days:





    My refrigerant-to-water heat exhanger has Entering Water in the upper 70° range (78° water right now):





    And I'm consuming on a daily average about 32 KWH (cyan line) for the GSHP system (pumps included):





    At $0.11/KWH, that's about $106 per month in the intense Texas heat.

    The two hardest parts of having a GSHP system are stomaching the up-front cost, and finding someone for installation with the advanced skills needed to insure getting some real value for the high initial cost.

    Best regards,

    Bill

  6. #6
    Join Date
    Feb 2003
    Location
    Huntsville,AL
    Posts
    4,125
    because of the even low possibility of ground water contamination, those installations are not permitted here!
    harvest rainwater,make SHADE,R75/50/30= roof/wall/floor, use HVAC mastic,caulk all wall seams!

  7. #7
    Join Date
    Aug 2006
    Location
    Dallas (Plano), TX
    Posts
    168
    Quote Originally Posted by cem-bsee View Post
    because of the even low possibility of ground water contamination, those installations are not permitted here!
    That's unfortunate for closed-loop, water-only GSHP installations, like mine. Here in the Dallas area, nothing but plain water is needed for the cooling loop.

    Best regards,

    Bill

  8. #8
    Join Date
    Jun 2008
    Posts
    5

    Talking

    Thank you all for the information. This has been very helpful. I'm going to get some additional estimates and bite the bullet. Now I just have to tell my wife that she can't have her new room for few more years!

  9. #9
    Join Date
    Aug 2006
    Posts
    2,609
    Quote Originally Posted by cem-bsee View Post
    because of the even low possibility of ground water contamination, those installations are not permitted here!
    Who's the dumb S*** that came up with that rule. Even in Maryland they usually use plain water, since the ground loop is buried deep enough to prevent freezing. Lets say you should have a catastrophic failure of the water/refrigerant coil, even without a loss of pressure switch the compressor isn't going to run more than a few minutes before it grounds and trips a breaker. I doubt more than a few tablespoons of oil would go into the water loop. I figure most vehicles would leak out hundreds of times that amount of oil in their lifetime. Added that it is a sealed loop with a relief device that is inside the structure, the oil is furthur contained. A small amount of water is hard to separate from oil in a sealed system. A small amount of oil in a water piping system is fairly easy to get out. Water source heatpumps have a much lower refrigerant leak ratio than air to air systems, a much higher service life, and dependability.

  10. #10
    Join Date
    Jul 2008
    Location
    DeLand, FL
    Posts
    37

    Air v Ground Source HP

    Are there any ground source heat pump owners on this board here in cent FL? I'm wondering how cost effective that equipment is here? It seems that after insulation, radiant barrier, desuperheater install that the addition savings with a ground coupled unit would not be practical. Anyone with experience here in FL care to comment?

  11. #11
    Join Date
    Oct 2005
    Location
    phoenix az
    Posts
    429
    Quote Originally Posted by jmueller View Post
    Thank you all for the information. This has been very helpful. I'm going to get some additional estimates and bite the bullet. Now I just have to tell my wife that she can't have her new room for few more years!


    That should go over real well hope you have a good doghouse
    "Do not let what you can't do interfere with what you can do"

    "Do what you can do the best that it can be done and no one will ever know what you can't do"

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