I am looking for responses from homeowners and installers about leaks or other failures in Direct Exchange (DX) systems. This is where the ground loop is also the refrigerant, saving a loop and increasing efficiency. It uses special copper pipe instead of plastic. Thousands of units have been installed but some experts are saying that leaks have developed allowing refrigerant to escape into the ground and into wells. Any comments?

I know of 30 - 40 systems that have been installed. None of them have leaks.

From what I have heard leaks seem to be the least of their problems.
 

Reliable oil return to the compressor and inability to accommodate two stage operation are a pair of other potential shortcomings of DX

The direct interface of copper refrigerant tubing with the ground is attractive for both its apparent simplicity and potentially higher efficiency, but the technology is not without concerns.

The "leaky refrigerant" argument is one water boys have used to argue against DX for years. It has lost it's merit by and large.
Flip said is the "DX is more efficient" argument made by the DX installers which is a little disingenuous as well. Ultimately all geo systems are limited by the ability of the soil around them to transfer heat. DX manufacturers use as much pipe in the ground as their system can effectively return the oil from. That will make them more efficient (by default) in some cases and less in others (dry sand comes to mind) due to the inability to increase footprint in extreme cases (water guys can simply add loops to compensate).
Most systems have extremely similar average COPs.
DX systems are more attractive to newbies as they don't have to purchase a bunch of new tools to work with it, so check references.
Good Luck,
Joe

I don't know about other brands but the Earthlinked loops come from the factory pressurized to 400 psi with dry nitrogen.  The dealer is supposed to test each loop after opening the box to ensure the loops held pressure in transit.  Any loops that did not have 400 psi after opening the box should be returned to the manufacturer.  So, the part of the loops that are inserted into the holes and grouted in shouldn't have a problem with leaking.

All the copper loops tie into a manifold at a depth of 3 foot and all the copper joints should be brazed in the field by licensed HVAC technicians.  Before being connected to the compressor, all the earthloop joints should be presurized to 400 psi with dry nitrogen and checked first for audible leaks.  If no audible leaks are detected, then each joint should be checked with an ultrasonic leak detector, bubble solution leak detector or an electronic leak detector.  If no leaks are detected, then the earthloop system should be held to 400 psi for 8 hours before the manifolds are covered up.  It's generally a good idea to submerge the manifolds in water and look for bubbles as an extra precaution before covering them up.  If, after 8 hours at 400 psi and there are no bubbles showing on the surface of the water, you have a solid installation in the ground.  Submerging the manifolds in water also helps compact the sand around the copper and minimizes the risk of soil shifting after the pit is covered with dirt. 

This is a fairly bullet proof installation procedure and, bottom line, a properly installed DX earthloop system may be a high bar for some technicians.  However, as an informed owner, you can ensure you get a good install by having a clear understanding with your dealer on how he plans on ensuring your installation will not have any leaks before you sign a contract. 

As HR Halderman told President Nixon after the Watergate scandal broke and Nixon was asking if there was a way to fix the problem.  Halderman told him that once the toothpaste was out of the tube, there was no putting it back.  That's the way earthloops are for both copper and plastic...once they are covered up, it's a major hassle to repair so your best dollar is spent making certain you don't have to dig it up.

I don't think the DX leak worries are about the installation Dale. I think what OP has heard is the age old concern that copper will rot in the ground and start to leak later.
You might share Earthlinks precautions about soil, that would be more to the point.
Joe

Just like the detailed installation procedure for assembling the loops before covering up the manifolds, Earthlinked has a specific procedure for ensuring the copper is protected.  Again, I'm not familiar with other brands but Earthlinked has been making DX geothermal systems since the mid-80s and, accordingly, I'm guessing have probably 10+ million hours of service on their equipment.  With all that experience, they have developed a thorough installation procedure to be followed and when it is followed, they have not experienced anything like Joe referenced or that Don asked about.

The procedure is basically to check the PH of the soil 3' below the surface where the manifolds are to be located.  Simply use a post hole digger to get a clean sample of soil at the 3' mark and send it to a qualified testing lab.  If the PH tests at less than 6, the loops will need cathodic protection and Earthlinked will warranty the loops for 20 years.  If the PH tests at 6 or above, Earthlinked will warranty the loops for 20 years without cathodic protection.  Either way, the loops are warrantied.

Having said this, there are not too many places in the United States where the soil would be so acidic that it would even create the need to install cathodic protection.  A peat bog or marshy soil are the kind of areas that might need cathodic protection.  So, a coastal area or a dry lake bed are potential candidates.

Gentlemen, I have been working with DX geothermal equipment since 1989. As a distributor I have sold more than 1000 DX geothemal systems since that time. There are two reasons the copper loops fail. The least common is soil ph. Ther eare not many areas of this country where the soil ph is aggressive enough to corrode copper that much. But the impressed voltage cathodic protection system netrralizes that compeletly. The mian reason copper loops fail is due to UNDERSIZING in heating dominate applications. a DX system can remove enought heat from the earth to freeze the soil to the point the soil "heaves". When that happens, the copper is moved and bent. Then when the ground thaws the copper is bent again. When there are enough of theses freezing and thawing cycles, the copper snaps and leaks. Of that 1000 systems, I ahve seen maybe 20 that developed leaks in the copper loops. Each time, the leak was near a solder joint at the manifold and the break was radial, like someone cut it with a tubing cutter. There is a lot of expense in cleaning up a leaking copper loop, lots of flushing and dehydrating and replaceable core filter dryers. But i can be done. The comment about not being able to do 2 speed or multi speed is accurate. The velocity of the refrigerant through the tubes is a large part of the oil return solution. If you use a "low speed" the refrigerant velocity slows and the oil does not return. Current designs do not address this, but I'm sure there will be solution in the years to come. FYI, on December 30th, I was called out to work on a DX system a former dealer had installed in 1990. The current owner is the 3rd owner and the unit had stopped running. BUT the unit had not been serviced in 15 years! Replacing a burned contactor and a dead run capacitor brought the system back to life. It is my opinion that once a copper loop is installed on a properly sized system, that copper loop can serve 3 or even 4 compressor units assuming the average life of a compressor unit is 20 years. That should be enough life. I cn remember how we heated and cooled in the 1950's and 60's. The rate of innovation we now see should make geothermal systems "ancient" by 2035 or 2040. A prospective buyer does not have to concern hmself with the life of the cooper loop. A copper loop will last a long time.

I have concerns about DX as notes above, but corrosion of the copper isn't one of them. I grew up in New England before PVC pipes were common, and copper was routinely buried deep underground (below the frost line) as the main domestic water inlet. I don't remember ever hearing of a corroded / leaking copper water line.

Actually Nordic has a multistage unit that a little bird tells me will control refrigerant much like Daiken very soon.

j

To Geo junkie:L Your 1/4 message was very helpful. You state that the main reason for pipe failures is "undersizing". Does this mean the size of the pipe or the size of the heat pump? I also have a chapter in my book abut Future Trends. You mention innovation changing the heat pump field. Can you give us an example of some of the changes coming?

Don,

Has your book been published?

The most immediate technology is variable speed equipment and electric TXV's. Instead of two stage the equipment will have infinite stages.
j

My book has not yet been published. I am finishing up a few details and my coauthor is putting some data together. Imwill go to the pubisher in about two weeks. It will be called "Say Goodbye to Oil —Everything you need to know about Geothermal Heat pumps" Here some question questions that may change my manuscript. These arise because of the comments on freezing earth heaves breaking copper pipes. FAQs in many geothermal company websitesl ask the question: If we add lots of GHPs will we not change the earth ground temperature? And the answer is always "no, because the earth is such a huge heat sink it is like trying to empty the ocean with a teaspoon. 1.So is not that an incorrect answer? At best, the answer may be that it changes it locally and temporarily. 2. What is the temperature of the DX refrigerant after it gives up is heat and goes through an expansion valve into the ground? It must be more than freezing so as to have a temperature difference. Or is it just temporarily inefficient until it travels 70' down and up 5 or 6 boreholes. 3. What is the output temperature (into the ground) of a conventional system? I have wondered why they use antifreeze and maybe the answer is that it sometimes is freezing also? Thanks

Outgoing loop temperatures are completely dependent on the system, climate, and loop. It is frequently below freezing, especially in the North where it is hardly ever cost-effective to put so much loop in the ground that you don't hit freezing temps at some point. There's nothing magic about 32F from the heat pump's point of view. You do get a significant benefit as the ground freezes and gives up latent heat - this will tend to stabilize loop temperatures until so much ground is frozen that the temp starts to drop again.

I don't want to give offense, but I can't think of a nice way to put this - if you are asking questions like this with 2 weeks until you publish, I doubt the book is going to be of much value. Do you have experts from the field involved in the project? Someone like an IGSHPA instructor or experienced engineer or installer? Maybe I misunderstood the question or the intent of the book - please disregard my comment if that is the case!

I think you'll need a little more research vs 1 paragraph blogs to adequately address this topic. As you are researching for profit, perhaps someone with a vested product interest (such as geo junkie or tuff luck) would like to spend that kind of time with you.
I mean this constructively. As it is a busy time of year for many of us, distributors mentioned above or manufacturers may be your best resource.
Joe

A fair question. I do have a co-author with 27 years in the business, has 15 years as an installer, accredited as an IGSHP trainer, is a GHP consultant in the US and Canada, founded his own manufacturing company. My book is written for homeowners by a homeowner, my experiences, but I do get into how it works, especially how the GHP system gets from 50 degrees to 165 degrees using the P/T relationship and converting compressor electrical energy into mechanical energy, and then into heat energy. My co-author has made numerous changes and agrees with everything else. He does have an earned bias against DX so I am trying to balance that with wider inputs. Our motivation is to increase public awareness of this technology because I found out that very few people understand what this is. I pesonally have no connection,agreement with any GHP organization . Just a retired engineering graduate with a lot of corporate experience in explaining technical subjects in easily understood English.

Since this is going in a book...a couple of points to reinforce something Geo Junkie said about the heaving.  This is only experienced up north (i.e. roughly above the Ohio River) and only when the unit is oversized for the home.  Just like down south where I am, oversizing always creates some sort of problem.  It was somewhat refreshing to read that issues driven by oversizing wasn't limited to humidity control problems though.

As far as changing the ground termperature...at least in North Texas, the seasons tend to keep the ground temperature balanced.  The mean ground temperature here is 67 degrees which indicates, on average, we will be taking a little more heat out of the ground in the winter than we will be putting back in the summer but not much.

Ummmm Dale, Mikes comment was that these failures occur when northern systems are UNDERSIZED...... (not yelling, he put it in all caps).
It does bring up the point that DX tends to 100% load which is a limiting feature in retrofit work where ducts may not accomodate....

Dan, a co-author with bias against a significant contributor to the industry sounds limiting. Many of the pros here are not dealers of DX, but not neccesarily due to a bias against the technology.
Amost all geo is good if properly applied and installed. Ignorance to the contrary is unfortunate in a reference book.
In my shoppers list of questions here and elsewhere, I commented that the most important thing is installer.......next most important is everything else!
You may quote me on that (I give you permisson on a public forum) :)
Joe Hardin
AMI Contracting
Howell, MI

Sorry guys.  I wish I could report that this will not happen again but the older I get...

I agree with Joe.  The difference is the installer.  All of this equipment works great if it's installed correctly.

Sounds like a worthwhile project - I wish you luck with it! To expand on my comment further, I think the issue of incoming water temp is a fairly fundamental one, especially for the uninitiated. When I am answering questions about my system, I'd say the most frequent question that comes up is why I need antifreeze in my loop since the loop is below the frostline and the ground temp is supposed to be "constant". When I explain that the loop temp can drop to 30F or even lower in mid-winter, people look at me as if I have two heads. There is definitely a perception that the incimong water should either be a constant 50F year round, or that it should at least stay above freezing (which the heat pump itself couldn't care less about as I said before). Hopefully you can address this in your book particularly given the target audience.

Hi,

          Interesting that you ask!  You might want to look at Faulty Earthlinked systems forum.  I have had nothing but problems with my DX system

Hello, Just to weigh in on the forum - we've celebrated our 100th DX system install and can tell you from experience PROPERLY SIZED AND INSTALLED the DX methodology is excellent. We've also installed several water loop systems and while they operate well they're a pain to install and cost more to run. The water loop folks keep saying DX will leak - and when it does it will be like Chernobyl - killing everyone within a 50 mile radius. DX systems properly installed will not leak in nearly all ground conditions. But that postulates they'll be properly installed. Unfortunately there are too few folks who "get it" and understand the configuration and field work required. Paul TotalGreenus.com

Define "several" and explain how a water source system is any more laborious to install please.
Note that I have made it a point as have many others here to say all systems are fine; installer is key.
I do tire occasionally of the "we're so picked on" complaints of some predominately exclusive DX installers.
Your exagerations do a disservice to your message.
Joe

Joe,

Sorry it's taken me so long to respond why we prefer DX to water loops. The drilling activities are dirtier than DX with more stuff to cart away, the flow centers and manifolds are more difficult to put together as opposed to simple brazing and high pressure testing, and start-up is easier (for us) using refrigerant than glycol or ethyl alcohol purging. In addition, you need less equipment with DX - the heat pumps are more flexible creating 100% DHW using a full condensing coil. We have over 100 DX systems and ten water loop systems.

I'm not exaggerating what some folks who install only water loops say about DX technology. There's one particular well driller in our region who has actually said what I've written - and consumers who don't know any better have been sold off DX. Every sale is a miracle - let's not give a prospect reason NOT to buy. You're hearing the "we're so picked on" because it's true. Give everyone a level playing field and may the best technology win.

What about acid soil etching the copper pipes? I have heard of problems after 15 years with these systems springing leaks due to pipe corrosion. If you already provided some historical data, I apologize for the repeat.

Posted By Paul Auerbach on 26 Oct 2010 11:03 AM
Joe,

Sorry it's taken me so long to respond why we prefer DX to water loops. The drilling activities are dirtier than DX with more stuff to cart away, the flow centers and manifolds are more difficult to put together as opposed to simple brazing and high pressure testing, and start-up is easier (for us) using refrigerant than glycol or ethyl alcohol purging. In addition, you need less equipment with DX - the heat pumps are more flexible creating 100% DHW using a full condensing coil. We have over 100 DX systems and ten water loop systems.

I'm not exaggerating what some folks who install only water loops say about DX technology. There's one particular well driller in our region who has actually said what I've written - and consumers who don't know any better have been sold off DX. Every sale is a miracle - let's not give a prospect reason NOT to buy. You're hearing the "we're so picked on" because it's true. Give everyone a level playing field and may the best technology win.

Sorry Paul, 
I can't abide by DX over water source propaganda.
Water source in my area goes 150'/ton vertical while DX goes as high as 600'+ for 5 tons. This is not a huge difference.
Horizontal loops for Earthlinked for example run in 125' x 4' trenches/ton while my slinkies run ~110' x 30" wide.
Can't hang with the less mess argument.
We also have a fairly recent post from a DX distributor who says DX designs for a higher percent of load than water source due to ground freeze (northern climates) which creates larger foot prints/tonnage.

I have no reason to suspect you are not one of the good guys, but can't let DX claim the moral high ground.

While you mentioned our flow centers, manifolds and antifreeze, you neglected to mention the nitrogen, oxygen, acetylene, braze rods and things unique to your product.....Oh and 30ish pounds of HCfCs.

BTW wish all you guys would lean on your manufacturers to get recognized by the ICC and answer the question of freon leak detectors due to the amount of HFCs in small resi systems.
Blame them for not taking the steps to legitimize their products.

Personally I like the product and think it has a place. I do not hang with the copper decaying in soil propaganda as it is in the soil here in MI naturally.

I also can tell you it is more expensive here than water source (unless I do not charge for the installation man hours which are greater). Certainly does not make that true everywhere.

I support dealer over product. 110 installations demonstrates your real expertise.
I'm cool with both of us backing our primary products and serving our customers the best way we know how.
Be well,
Joe

I echo a low concern with buried copper lines.

I'm attracted to the simplicity of DX as well as potentially better efficiency, but I share Joe's concern about the much higher volume of refrigerant.

I believe the future of HVAC lies in variable speed modulating compressors able to drop down to 25% or less of full load. Until DX works out the resulting refrigerant velocity and oil migration issues, it will remain on the margins.

If you have low PH in your soil , it stands to reason that over time you will get metal migration/etching. I've been told by people in the Northeast that DX buried copper for 15 years sprang leaks losing freon to the ground. The system was costly to replace. I am really curious about the low concern here. What history data can you provide to counter what I've heard? Why would I do geo with metal when hdpe can last 50 years +.

Posted By gonegeo on 28 Oct 2010 09:23 PM
If you have low PH in your soil , it stands to reason that over time you will get metal migration/etching. I've been told by people in the Northeast that DX buried copper for 15 years sprang leaks losing freon to the ground. The system was costly to replace. I am really curious about the low concern here. What history data can you provide to counter what I've heard? Why would I do geo with metal when hdpe can last 50 years +.

gonegeo,
There are 30 year old systems operating in MI.
It is true that some soils are not suitable for DX lines. First step in installation guides of two different systems I'm trained in is check ph. If it is outside of parameters a sacrificial rod is installed (much like a water heater) although one distributor told me privately he simply wouldn't "go there". Earthlinked had 25 year loop warranty last I checked.
Hdpe if backfilled with sharp gravel or boulders would expand and contract its way into leaks after a while.....
Like anything else, if manufacturers' instructions aren't followed, bad things happen. It's not the product or manufacturer's fault, it is the dealer.

Sooooo...........pick a good dealer and everything else will be less important.

Hope this helps.
J

I think the question is "if" you have low PH in your soil.  A soil PH below 6 in the United States is rare.  In Texas, all our soils tests for the DX loops have come back between 7.5 to 8 which is covered by the Earthlinked warranty.  I have talked to DX installers around the country who have installed thousands of the DX systems and I have only found 1 instance of this type of condition actually happening in the field.  It was in the Cleveland area and the home was sitting on top of an old lake bed that was basically a peat bog.  In this instance, the installer simply didn't do his due diligence when evaluating the job site.  If he had done a soils test and followed the manufacturers recommended installation procedure and installed cathodic protection on this job, it would not have had the costly expense of replacing the loops.

Within the past year or so, Earthlinked has tightened up their installation requirement even further by requiring cementious grout for the loops.  Cementious grout is alkaline and anything aklaline will have a high PH.  So, in the ground, the copper loops are even less susceptible to this problem because it is encased in a high ph cementious grout.

Here in Texas, copper water pipes were required by code for eons until pvc and pex water supply lines came along. No one around here had heard of this problem until the folks pitching plastic water loops for geothermal started talking about it. Everything I have been able to dig up (no pun intended) on this matter indicates this is an issue driven by DX business competitors rather than an engineering issue.

Posted By 183eej on 29 Oct 2010 08:56 AM
A soil PH below 6 in the United States is rare.

Maybe that's true for Baja Oklahoma, but I don't believe it
applies to huge areas of the right coast covered in red oak
forests with plentiful rhododendron and mountain laurel.

I haven't checked in here in a while and I'm not in the bussiness. However my DX system is still going strong since 1994. No problems with the copper so far. There is so much copper in the soil around here there are green flakes in the rock. When my US Powers system was installed they did a soil ph test and said it is fine as is. No cathods needed. I have a horizontal coil in rocky soil. I have replaced one compressor 2 years ago and an A coil a year ago in the air handler. It is a conventional Trane air handler and I've never been happy with it's ability to carry off the condensate water made during air conditioning. I think that has alot to do with the A coil leak. I replaced the Desuperheater at the same time as the A coil with an updated unit while the system was depressureized. This one gives me great hot water even in the heating mode. Compared to the neighbors bills mine are nearly 1/2. Most of my neighbors have already replaced their entire conventional systems some time ago. Put me firmly in the DX corner. If I was building again tomorrow 1st thing on the list would be a new DX system!

Kinda funny the talk about DX fouling the ground water. Never heard that before. In this state there are several wells fouled with anti freeze by leaking water based systems that were installed by a dealer who didn't know what they were doing. It all goes back to who did the job of installation. US Powers went out of business a year after my sys was installed. The dealer that installed mine still has several systems they installed around the same time out there running fine. Another dealer that installed these same systems locally have given DX a bad name as most of their installations failed long ago. Sized and engineered wrong for the application among other problems.