Any opinion on direct exchange systems versus water based?  Does anyone have experience with this manufacturer: LINK
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!

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.

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.

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.

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.

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

www.earthsource-energy.com www.dehydratedgeothermal.com Look into these links for more info on DX.

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.)

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.

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.

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.

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.

Lots of good information. Thank you. Which DX systems do you recommend?

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

Bunt

I'd go with the Earth Source system. Easier to service and better warranty.

I've decided not to. Mostly based on cost. I'm going to be using a Daikin split system variable refrigerant volume air-to-air heat pump. It has a COP around 3 at 10°F. Auxillary electric doesn't kick in until 10°F. Our design temp for heat is 9F, which means the heat pump will be extracting heat from the outside air pretty much all the time.

If this heat pump didn't have the performance capability all the way down to 10F I'd still be going geosource.

Only time will tell if it was a smart move or not.

Dmaceld, I'm in the same boat, looking at geothermal but cost is a serious factr. Someone recently placed a link to a new company in Maine that makes an air-to-air hp that can provide heat to -17 degrees F. You may want to look at www.gotohallowell.com. Dave

The Hallowell unit looks promising but there's three big differences between it and the Daikin. The Daikin can handle up to 8 indoor units with one outdoor unit. The Hallowell, one. There's about six configurations, and several sizes within each, for Daikin indoor units. Hallowell has only a couple it looks like. The Hallowell is a step variable flow system, meaning it has three compressor stages (two primary & one booster) with each stage either on or off. The Daikin has a continuously variable speed compressor, meaning the compressor can run at a very low speed and still pump refrigerant even when the demand is low.

The multiple choices of indoor units lets you pick what fits best from a regular ducted air handler to a small wall mount one room unit. You can also have the house zoned by individual units. This is a real consideration if you want to heat your garage. The IRC prohibits any interconnection between the living space and garage which means you have to have separate heaters for each. With the Daikin one outdoor unit supplies both. I'm using a 12,000 Btuh wall unit in the garage. The outdoor unit will supply it by itself if its the only one that needs to be running.

The continuously variable feature means the compressor can run more hours and adjusts its output to the demand. Contrary to common first thinking, equipment lasts longer the more it can run continuously. Starts and stops are hard on compressors. An electric motor that can run continuously will last longer than one that starts and stops in terms of runtime hours and possibly even in terms of calendar time.

I know this might sound like a sales pitch, but if it does it's because I've bought into it and those are the reasons I'm going with the Daikin. Plus, my nephew HVAC contractor is sold on them and wants to install one in my house.

There's no doubt the Hallowell system looks good, and may very well be the best choice in certain situations. In fact, I told my nephew a couple of weeks ago he needs to look at them as a possible product line.

The capability to put out heat at lower temps is a definite plus for the Hallowell, but that's a capability I don't need.

They use the ECR system, correct?

The EarthLinked system is the one with the most proven refrigerant controls. Just make sure the one you use is ARI and ETL certified.

EarthLinked was the original ECR unit. It was ECR Technologies, Inc., not to be confused with ECR Industries. Now ECR Technologies, Inc. has changed their name (trying to avoid any confusion with ECR Industries) to EarthLinked Technologies, Inc.