Geo Thermal

doogan123December 30, 2006

Hi everyone and Happy New Year. I hope its happy and healthy for everyone.

My question here is about Geothermal and specifically DX Vs Reqular

I have read the primary differances between them is that one circulates a water/anti-freeze mix thru a plastic type pipe and then exchanged into a refrigeration unit. The DX is basically an extension of the refridgeration unit into the ground

What are the benefits and disadvantages of either. I am finding it hard to get information about the DX system. I guess my primary concern is the life of the copper pipe in the ground..?

Which is the more commonly used system.?

which is the better system..?

Can any installer install either one..?

I would really appreciate any information on this topic as i need to make a decision pretty soon. Are there any sites that have more information on this topic..?

thanks in advance to everyone


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Look here.

    Bookmark   January 2, 2007 at 10:09PM
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Look here too, as well as at the 'Nordic' link in the previous post.


Here is a link that might be useful: DX Geo/ GW

    Bookmark   January 3, 2007 at 1:08AM
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Thanks for your replies. I have read those posts in detail and have also done some more research. It does seem that a DX system is extremly efficient if correctly installed. It also appears to be more affordable. I would still like opinions on a couple of points. .....

Assuming neutral PH, What is the expected life of the copper in the ground..?. Is this something that one should expect to replace after 10 or 20 years. ?

What is the impact of a refrigerant leak into the ground? is this of the same magnitude as an oil leak interms of impact to the envirnoment, or is the refridgerant less toxic. I have heard that it evaporates, however how can that happen 100ft down..?

    Bookmark   January 6, 2007 at 11:32PM
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Re: doogan

Copper is still the Âgold standard in plumbing. How often do the cold water mains into your house have to be changed, every 50 years, give or take? Why? Usually not because of corrosion, but because of restricted flow caused by a buildup of mineral deposits.
DX ground loops should last 50 Â 75 years. Should the refrigerant leak itÂs probably more of a hazard to the atmosphere than to the ground or ground water. The liquid anti-freeze in a conventional geothermal system would likely be more harmful to the ground and ground water than Freon. An oil leak, if sever enough, could be a catastrophe both environmentally and financially, which is why we moved away from our oil furnace.

I donÂt loose any sleep over our DX ground loops. The whole system has been surprisingly and absolutely trouble free! I kind of view the whole controversy as somewhat akin to the debate of, Âwhich do you prefer, PC or Mac? Personally I prefer the Mac.

In the link below, the top picture with the blue drill rig was taken in our front yard next to a flowerbed. The drill bit sticking up out of the ground is the size of the borehole, only 3 inches in diameter. The entire Âbore field is not much larger than that patch of grass in the picture. This company did not do our installation, but Âlifted the picture from elsewhere on the net.


Here is a link that might be useful: Lysair

    Bookmark   January 7, 2007 at 1:51AM
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Thanks SR - I am pretty much at the point where i will be starting to locate and speak with installers to get an idea of the cost differance over installing a regular conventional system.

How does your system manage with the home hot water needs. Do you need an additional water heater? or will the system generate enough hot water for a family (Kids baths, showers etc etc)


    Bookmark   January 7, 2007 at 11:07AM
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Re: doogan123

The year before we installed the GSHP, we installed a stainless steel HW tank that has turned out to be incompatible with the HP desuperheater due to an internal cold water-mixing valve that reduces the tankÂs stored water temperature from 175ºF to a nominal 120ºF at the tap.
The bottom line that anyone should be able to relate to is our home is 2400 Sq. Ft. with 4 people, in Montreal Canada (cold winters & warm, sometimes hot summers). Our only energy source is electricity and our total electrical consumption over the past full year was 18,038 Kwhrs.


    Bookmark   January 7, 2007 at 5:24PM
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We are preparing to build our own home and have started looking into this DX system. It will be in Ottawa - so same as you, cold winters and hot summers (really humid days sometimes). Can the system actually cool your home during the summer? How good is it compared to a regular AC unit?


    Bookmark   January 8, 2007 at 10:54PM
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Re: joseph007

The system works very well in the A/C mode  even on the hottest days and is probably 40Â45% more efficient than either a standard air-conditioner or air source heat pump. Imagine it this way; instead of dissipating the heat from your house into the hot, humid air that may be 28ºC or higher, youÂre dissipating it into the cool ground, which is about 6ºC (close to what itÂs been the past few days). Also, you do not require that big noisy fan found in heat pumps or air-conditioners; the cool ground is doing all that work - free! Instead of half your system sitting outside baking in the sun, the whole system operates indoors, in its own air-conditioned comfort. Putting you hand on the heat pump cabinet in the A/C mode is like opening you refrigerator door and touching an inside surface panel. ItÂs actually quite brilliant.

If you send me an e-mail through Garden Web, IÂll put you in contact with the right people in Ottawa.


    Bookmark   January 9, 2007 at 1:02AM
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We are on our third different kind of drilling rig to get geothermal. 80' under philadelphia, in Fishtown the landscape is kind of tricky. running sand and boulders, apparently. But it is worth it with all the news about global warming. Maybe that DX system would be better.

We are going to sell a green built condo. There is tons of development here but it is mostly driven by developers seeking to double their money and not interested in better building envelopes.

My realtor says no one cares about that sort of thing when they buy but I can't see building a place any other way.

    Bookmark   January 9, 2007 at 3:55PM
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Re: frankjones5

Your realtor lacks the vision to see a future beyond his next commission check.

Are you going to sell one condo unit or many? Is this your first borehole that at 80 ft. youÂre Ârunning sand and bouldersÂ? That sounds rather strange. I would expect youÂd be into solid rock long before that. Scrutinize your drillerÂs credentials more closely if itÂs not already too late.

Since you are having real difficulties or even perceived difficulties, I would suggest proceeding with caution. Consult detailed geological maps for your specific region, area and location to determine with as great a precision as possible just what exactly is down there. This information does exist and is worth seeking out; the US Geological Survey might be a good place to start.

I would go with a conservatively designed HDPE/liquid system. Something anyone specializing in geothermal can troubleshoot and service. The last thing you want to hear, should you later have any trouble is, Âwhy didnÂt you go with something more conventional?Â

Last, but probably first, I would want to talk to an IGSHPA certified geo-exchange designer in your area. ThatÂs the person who will likely have all your answers. They will likely be a professional engineer as well.

Good luck; keep us posted.


Here is a link that might be useful: IGSHPA - Certified GeoExchange Designer

    Bookmark   January 10, 2007 at 1:13AM
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Thanks SR for your reply (I just realized I did not reply to you yet). Any contact info you have for the Ottawa area would be nice - (I've sent you an e-mail as suggested).

I'm just now starting my research into this system (I had never heard about this before until recently).


    Bookmark   January 12, 2007 at 8:34PM
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Yeah it's 75 to 80' before you hit bedrock. Apparently it used to be the ocean here 65 million years ago. I could see the senario where there is kind of a water table on top of the bedrock.

I did do a little research and I even told the drillers before they showed up but did they listen? No. They just figured they would come out and see for themselves.

    Bookmark   January 13, 2007 at 2:08AM
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