Opinions on DX (direct exchange) systems
Last Post 17 Feb 2008 11:18 PM by tuffluckdriller. 25 Replies.
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MerlinMcUser is Offline
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19 Jun 2007 01:34 AM
Any opinion on direct exchange systems versus water based?  Does anyone have experience with this manufacturer: LINK
Thanks very much.
dmaceldUser is Offline
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20 Jun 2007 02:01 PM
Posted By MerlinMc on 06/19/2007 1:34 AM
Any opinion on direct exchange systems versus water based?  Does anyone have experience with this manufacturer: http://www.ecrtech.com/content/

Thanks very much.

Can't tell you much right now, but I'm planning on using their system for the ICF house with radiant heating/cooling I'm getting ready to build. My HVAC contractor nephew-in-law is working with me on the system. His shop foreman, and one of his supplier distributors, is really impressed with the Active Charge Control system ECR uses. He tells me his shop foreman is practically drooling at the idea of installing one of those to see how well they work! He also is convinced the heat pump efficiency will be greater than with water loops. I will probably bury the outdoor refrigerant lines in trenches. I'm  having a problem finding someone to drill 2 to 3" diameter vertical holes.
I can probably tell you a whole lot more a year from now!

Even a retired engineer can build a house successfully w/ GBT help!
wallers164User is Offline
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13 Jul 2007 09:23 AM
DX geothermal is the best way to go for residential and small commercial buildings. In the future it will be developed for larger structures. This has been around for over 30 years but is not well know among the general public. ECR (www.ecrtech.com) and EarthSource Energy Solutions (www.earthsource-energy.com) are the two DX producers in US that are certified by ARI. You won't go wrong with either.
Jim Smith
EarthSource Energy Solutions, Inc.
1415 Beacon Street, Suite 200
Brookine, MA 02446
jsmith@earthsource-energy.com
megatekUser is Offline
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29 Jul 2007 11:09 AM

Each approach has its own benefits and drawbacks - i can only speak as to the benefits of water-source heat pumps (as that is what i do):

Water source Benefits
plastic (high density polyethylene) piping (similar to gas piping) installed in the ground will never corrode, as copper may

lots of installers of ground loops are available nationwide

heat pumps are pre-charged with freon from the factory, and do not need the refrigerant circuit to be assembled in the field

less temperature impact on the localized soil (loop temperatures are mild) which means you dont need "soaker lines, etc

federal and state and utility incentives ranging from several hundred $$ per ton in rebates to reduced electric rates (some areas as low as $0.028 per kWh for geo! (western des moines, IA))

allow for multiple heat pumps hooked to one ground loop (increased efficiency from heat pumps cancelling each others effect on ground)

you arent putting freon into the ground "loop" but rather a food grade, non-toxic antifreeze solution (often found in shampoo, i.e. Propylene Glycol)

Great topic . . .

John Herbert
Sales Engineer
www.hydroheat.com
andy351User is Offline
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07 Aug 2007 12:01 AM
I live in the Kansas City area and had a DX ground source unit from a company called Dressler who is now out of business with 2000 ft of 1/4 copper filled with R-22 6foot deep. It ran great for @15years and then had problems with lines starting to leak in the ground and have talked to many others in the area that have had the same problem. If you go DX be sure you check into ground anodes to help get rid of the galvanic reaction that will for sure happen just be sure to control the corrosion.
tuffluckdrillerUser is Offline
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03 Nov 2007 01:47 AM
DX systems will work wonderfully if installed properly. We've installed over 100 ECR EarthLinked systems since 2001, and have seen wonderful efficiencies from them. We checked a 4000 sq. ft. house's sub meter last month. In 21 months, he's averaged $42/month for heating and cooling.

We have been installing geothermal for just over 13 years now, and we're more impressed with the simple and maintenance free ground loops of DX systems vs. water source.

As far as corrosion on copper, as long as manufacturer recommendations are followed by a qualified installer, the loop should last forever. Copper is a natural element. We get it from the ground. If the ground naturally corrodes copper, how do we have it?  There are some corrosive environments that can be a problem, but that's where the impressed-current cathodic protection comes in. I would have to assume that anyone experiencing a leak in their copper loop had it installed without checking the pH of the soil, installed it too close to a septic drain field, too close to barnyard runoff, or undersized the system. Also, the refrigerant in the system is an inert gas. It can't, and doesn't support electrolysis inside the tubing.

One other benefit of copper vs. plastic is the type of heat exchange done in the earth. With plastic, it does a sensible heat exchange. A way to explain that is that it must pick up degrees from the earth, not necessarily BTUhs. The copper does a latent heat exchange, (exchanges BTUhs), which will have a larger range of being able to pick up heat from the ground.

In trying to explain the latent heat exchange...the copper with refrigerant does a phase change in the loop--it must boil the refrigerant, or change it from a liquid to a gas. With refrigerant, this can happen down to about -44 deg. F. That's not to say that we want to get the earth that cold (that's where proper sizing comes in). As long as we can have this phase change, we can extract energy from the earth to heat the home. With plastic/glycol loops, it's not a phase change needed. It's a sensible change. When (if) the earth loop water temperature nears about 20 deg. F., the sensible heat exchange is about finished. At that point, supplemental heat must turn on to replace the heat pump's output. This can many times be remedied with proper sizing.

A huge benefit of this latent heat exchange is that the ground loop is factory designed/engineered. The heating contractor doesn't need to have any guesswork or expensive test bore hole to find out the thermal conductivity of the ground. Instead, we need to know only the mean ground temperature and pH of the soil.

Another benefit is that copper conducts heat many times better than plastic. This allows for the footprint to be considerably smaller. A 6 ton system's vertical loop can take up as little as a 14' diameter circle. This fits on many more small lots than plastic loops.

I'm also a driller and have a sonic drilling rig, mounted on tracks. There are few places I can't get my rig to fit the small footprint of the loop, and I only have to drill 100 feet per ton (in my area--needs more if the ground is 60 deg. F. or warmer to handle the cooling needs).

Water source geothermal has it's place (larger commercial), but having a lot of experience with both water and DX, there's no comparison in my mind.

Clark Timothy (clark@pinksgeothermal.com)
Geothermal Heat Pumps: Heating and Cooling that's Dirt Cheap!
www.pinksgeothermal.com
BenWillemsUser is Offline
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04 Nov 2007 05:32 PM
How do the prices of DX vs. water ground-loop compare? Can you do something similar like water to water when you want to heat your radiant floors?
dmaceldUser is Offline
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04 Nov 2007 06:27 PM
Posted By BenWillems on 11/04/2007 5:32 PM
How do the prices of DX vs. water ground-loop compare? Can you do something similar like water to water when you want to heat your radiant floors?

Dont' really know, and yes. I think the heat pump equipment is about the same, maybe a bit more. Biggest difference would be in well drilling cost if you compare to closed loop water. That's because I think the water loops require about 1 1/2 to 2x the loop length of the DX loops. If you can go with open loop water, i.e., pump and dump, and dump into a cistern that would probably be less. But water quality is a serious issue with pump and dump.

ECR Technology offers both water heating modules and air modules for the in-house side of the system. They also offer a domestic hot water module and the system can be configured to produce hot water year round.

I don't know what Earth Source Energy has available. Their web site is seriously short of product and technical info.


Even a retired engineer can build a house successfully w/ GBT help!
wallers164User is Offline
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30 Nov 2007 03:48 PM

DX systems are great if they are installed properly. One should not use an installer that is not fully accredited by the manufactured product. They pay-off period is worth.
JIM

Jim Smith
EarthSource Energy Solutions, Inc.
1415 Beacon Street, Suite 200
Brookine, MA 02446
jsmith@earthsource-energy.com
Paul AuerbachUser is Offline
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13 Dec 2007 12:26 PM
When determining which geothermal methodology to use for our clients, we did exhaustive research.  DX installed correctly is more efficient than water/glycol, will last as long or longer than water based systems, and eliminate the pumping stage required with horizontal or vertical water loops.  There are certain applications for water based systems determined on a case by case basis.

FIND A COMPETENT INSTALLER is the best advice we can offer.  It's great how geothermal is finally gaining market penetration.

Regards,

Paul Auerbach
Total Green, LLC  Serving the Catskills
Northern NJ and Hudson Valley NY
371 Orchard Drive
Monroe, NY 10950
DakersUser is Offline
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15 Dec 2007 08:28 AM
www.earthsource-energy.com www.dehydratedgeothermal.com Look into these links for more info on DX.
davewUser is Offline
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14 Feb 2008 09:10 PM
As far as corrosion on copper, as long as manufacturer recommendations are followed by a qualified installer, the loop should last forever. Copper is a natural element. We get it from the ground. If the ground naturally corrodes copper, how do we have it?


Metallic copper exposed to oxygen will turn into copper oxide. Metallic copper is, well, copper colored. Oxides of copper are generally green or blue. You can see this process happening on many fine statues and state capital roofs. Ph, temperature, and other chemicals can affect the rate at which this reaction happens, but it will happen. The process does not destroy the copper atoms; it just combines the copper atoms with oxygen atoms to form a new chemical. Now copper oxide is pretty cool stuff because is not soluble in plain water, and it forms an airtight surface barmier which protects the bare copper below from further damage. Iron oxide on the other hand is water soluble and does not form an airtight barrier. Iron can rust completely away in relatively short order. One of your neighbors probably has an old car that is proving this as we speak.

Now here's where my chemistry runs out. I don't know what else may be going on in the soil to cause the pipes to decompose further. Maybe acidic soil can dissolve the copper oxides. Anyway, how confident are DX installers in the life span of copper pipes buried in the ground? Where does the data come from that will tell me how long I can expect the copper pipes to last? DX systems haven't been around that long. Is there some older application that involves buried copper pipes that can provide some answers?

These systems are not cheep. Before I plunk down $20k or so I'd like to be able to come away with something more satisfying than "hire a good installer." Also, given the time spans we are talking about warranties aren't as useful as most people think.

(As I read back over this the first part sounds a little bit condescending. I don't intend it that way. I just want to get a few facts out on the table to set up the questions that follow.)
tuffluckdrillerUser is Offline
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14 Feb 2008 09:48 PM
As long as there is a pH of 6.0 or higher, copper will not naturally corrode. That's right, I said will not. As long as the refrigerant remains as an inert gas, there can be no corrosion from the inside. If the soil is acidic, EarthLinked Technologies (ecrtech.com) has an impressed current anode/cathode protection system. This uses a very small amount of power to constantly bombard the copper loops with electrons, replacing any that are taken from the copper due to acidic soils.

Test the soil before installation. The USNRCS (US Natural Resource Conservation Service) will perform a pH test on soil for free. Most colleges/universities will, too. I've never found soil with a lower pH than 7.4. I've tested all over Utah. If the corrosion protection system is needed, because it's an impressed current, we expect it to give at least a 50 year life to the copper.

As far as the oxide on copper is concerned, you are dead on. It forms a protective layer.

DX is definitely the best way to go. No loop maintenance, no pump maintenance, and no loop maintenance. We've been doing geothermal for over 13 years now. We switched to just EarthLinked DX in 2001. I'm sick of still having to purge and pressure the water ground loops, replace pumps--even though it's not necessary until 3 to 6 years pass by, we're the only ones in the area who have a purge pump and know how to do it.

One big reason on finding and using a qualified installer is that incorrect sizing can cause a copper loop to eventually fail. This is not because copper corrodes in the ground, but that some dumb installer didn't do it right, and just gave it a bad name in that area. We don't need that happening. Sizing is not really difficult, but is critical.

Oh, one more thing, as far as I know, the oldest EarthLinked unit has used the original ground loop for just over 20 years now. There may be older copper loops out there still being used.
Clark Timothy (clark@pinksgeothermal.com)
Geothermal Heat Pumps: Heating and Cooling that's Dirt Cheap!
www.pinksgeothermal.com
dmaceldUser is Offline
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14 Feb 2008 11:40 PM
Posted By davew on 02/14/2008 9:10 PM
Is there some older application that involves buried copper pipes that can provide some answers?
Before poly pipe became the norm lots of houses had copper water main lines from the meter to the house. I don't recall ever hearing of a copper water main corroding and I'll bet some of those have been around for 50+ years.

Even a retired engineer can build a house successfully w/ GBT help!
DakersUser is Offline
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15 Feb 2008 04:08 AM
As an experiment, a DX copper loop was removed from the ground after 22 years of service. Less than 2% of the copper had deteriorated. DX copper loops carry a 20-55 year warranty.
davewUser is Offline
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15 Feb 2008 08:47 AM
Thanks for the responses, guys! This is exactly the sort of information I was looking for to make an educated decision. This forum is really remarkable.
MerlinMcUser is Offline
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17 Feb 2008 01:05 AM
Lots of good information. Thank you. Which DX systems do you recommend?
BuntlyUser is Offline
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17 Feb 2008 11:56 AM

Dmac, let me know if you go with dx system. I am curious as to what you think of the system.

Bunt

Bunt
DakersUser is Offline
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17 Feb 2008 01:59 PM
I'd go with the Earth Source system. Easier to service and better warranty.
Paul AuerbachUser is Offline
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17 Feb 2008 02:31 PM

FIND A COMPETENT INSTALLER

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