Well Im sure this is a one thats been done here before but i want some peoples take on this. Ive installed both and my minds made up.....water loop is the one for me!

What do you think is better about a water loop?

We've installed both, and EarthLinked DX is far superior. It's easier to install, takes less room, is more efficient, and has far, far less maintenance. In fact, there is no loop maintenance, unlike we know water loops to have.

I don't want to see some war of words of water vs. refrigerant loops. Obviously, both work. Each system has its advantages and disadvantages. Each has its limits. Both systems use refrigerant to convert the earth's stored energy into heat for a building. Both work on the principles of refrigeration. Improvements are constantly being made (hopefully).

The bids are starting to come in, and as fate would have it, the DX and one open loop bid seem to be matched almost exactly as to price. Obviously the DX bid does not include the price of the water well I will need to drill for household use. But the well I would need to drill for double duty for household use AND open loop is just about equal the combined price of the DX drilling and the drilling for a simple household use well. Which means, we are in a dead initial cost heat.

So here is what I have heard as positives to DX: open loop takes a much bigger pump that must run very often, resulting in much larger electric bills than DX. DX eliminates the need to deal with surface discharge water. DX cannot cause problems inside of the heat pump the way well water might. DX is more efficient in that you don't need to convert water heat into refrigerant heat.

And here is what I have heard as positives of open loop: I need to drill a well anyway, so the one well will have double duty. Open loop is more efficient owing to its use of ground water, which is more difficult to cool down and cause reduced efficiency when compared to heating/cooling the earth immediately around the copper pipe of a DX system. Water is completely inert and unable to cause a problem in the soil if ever there was a leak, unlike the refrigerant in DX. The most popular DX refrigerant is due to be phased out soon. Copper is more prone to breakdown in the soil than a pipe (PVC?) carrying only water.

And the closed loop people have not even weighed in yet! This is going to be fun!

So what says the forum? I would suggest we avoid mere conclusions of which is "the best" and focus on those "advantages and disadvantages".

As always, I greatly appreciate your thoughts and opinions.

NickB

OK....

First of all, copper will not corrode (or breakdown) in the soil if it is a pH of 6 or higher. Have your soil tested. I'll be surprised if it's lower than 6.0. This is just a fact. Copper is a natural element that comes from the ground.

Next, the refrigerant can be R-22 or R-407c, or a number of other refrigerants. Currently, EarthLinked uses R-22 or R-407c. R-22 is more popular because it is more efficient than other refrigerants, and it's also the cheapest one out there. That will change with its phase out.

Because the refrigerant inside the copper loops is an inert gas, it will not corrode from the inside. END OF STORY, PERIOD END!

Open loop is not necessarily more efficient than DX. What COPs are they claiming? We routinely test and see COPs of 4.5-5.5 at the end of winter. That doesn't mean that's the ARI standard, but that's what we actually see in the field.

Now I must say why we first looked into DX. It's because of maintenance on water loops. Open loops have annoying, regular maintenance issues, too. Constantly replacing solenoid valves, pumps, etc. for open loops is a headache to the installer and the home owner. Maybe the installer doesn't mind because it's job security. But I don't like to stick people with maintenance issues. It just doesn't sit right with me.

Open loop systems can be very good if the water is good, and plentiful--and that there's an easy way to dispose of the excess. I'm in a desert dry climate. We've had way too much drought to want any kind of open loop, unless they have a free flowing artesian flow/spring with plenty of flow for the needs of the system.

If both systems cost virtually the same, then look at the maintenance. Have your water production proven. Have it tested. Make sure you're not stuck with a maintenance issue. Then, if everything looks the same still, at least you have 2 good options to choose from.

Also, try to make sure they are reputable companies. (I know that's not always the easiest to find out)

Keep us informed.

As a newbie what’s the difference between them, in layman’s terms?

Open loop, I imagine is take ground water out and dump it back someplace else.
Closed loop, the same water or water/anti freeze is pumped in circles in the pipe.

Then these are in a well (vertical) or horizontal fields

But what is DX?

A DX is a closed loop system that uses a copper loop with refrigerant in it. It is called DX in reference to its "Direct Exchange" with the ground.

Any open or closed loop water based system using poly pipes has 3 heat transfers. The basic path from the earth to the home goes like this: from the earth, to the water, to the refrigerant, to the air or water heating the home.

A Direct Exchange or DX system skips the water step. It goes like this: from the earth, to the refrigerant, to the air or water heating the home. Because it skips the water step, it can be more efficient, and less maintenance.

Clark:

Because I lived right next door to the lot where I am builidng, I have a pretty good idea of the water I will hit. I predict it will be excellent quality, plentiful, and since the land runs down to a beaver pond, I have an ideal way to get rid of the excess. Assuming all of that, as well as equally reputable dealers....am I finding myself in a situation were open loop might make more sense? I know you are in a desert climate, but I am in New England. Water is almost a nuisance here. I know what you are saying about the maintenance, but is that enough of a factor to nudge me toward DX?

I also know these are tough questions, but I want to avoid what I feel is the tempting cop out answer of "it comes down to personal preference." That works for music, clothing, values, etc. But in a sense, we are all in the same boat: wanting to heat and cool or homes as efficiently and inexpensively as possible. This is not about personal preference. It is about making the right choice. What do you think??

Thank you.
NickB

Listen everyone is entitled to there own opinion. Ive also installed both. Hey maybe copper ism fine in the ground its used for water maines. Yes DX will be SLIGHTLY more efficiant to run. But I do not like refrigerant in the ground....PERIOD. Dont tell me R-22 will not harm the soil what so ever. We use glycole and water. To me thats more natural than oily refrigerant. Theres a reason why oil tanks are not allowed under ground anymore.  No one has banned water under ground! Hey to each is own......My house is getting done this year in Geo Comfort closed water loop thank you.

I've stayed out of this debate since I don't really have strong feelings one way or the other, but I can't resist jumping in. I think someone on another forum referred to DX as the "Apple Macintosh of the Geothermal Industry" which seems very apt! Proponents seem to be very enthusiastic, almost evangelical while detractors are equally eager to point out the flaws. I think the discussions I've seen here have been very informative and both "sides" are being open-minded and avoiding rhetoric - very refreshing to see on an internet forum!

First, let's get open-loop vs closed loop/DX out of the way so we're comparing apples to apples. Never having owned or installed one, I'm going to play the armchair engineer and say that IF you have a very abundant water supply close to the surface and IF you can easily dispose of it, and IF the water isn't really nasty with minerals etc open loop will have lower install and running costs than either closed-loop or DX. Those are some big ifs, though! Maintenance may be an issue depending on water quality and design.

Now comparing closed loop and DX, it is clear that either system will work efficiently and reliably when installed correctly. Conversely either system will fail miserably if poorly designed or installed. In my mind there are 2 questions - which one is better when both are installed optimally, and which one is easier/more susceptible to screw-ups in design and installation? Let's look at some of the differences.

1. Copper refrigerant lines vs. HDPE water/antifreeze lines. This seems like a non-issue to me, although it gets a lot of attention. Yes there are a few areas where soil conditions will corrode copper, but in the vast majority of the country copper has a very long life span when buried underground. Similarly, unless you drop lots of very sharp boulders on it when backfilling, HDPE will probably outlast the heating system, house, and owner. So on the whole I think longevity is a wash. The much higher conductivity (something like 1000x higher) of copper is frequently mentioned, but in ground loop design I believe it is not terribly relevant. The reason for this is that the soil conductivity is usually far more of a limiting factor than the pipe conductivity. Just for fun, I calculated my required loop length using copper instead of HDPE – it reduced the required length from 3600 to 3200 feet, not a huge difference (if anyone wants to donate 3200 feet of ¾” copper pipe, I’ll try to verify this). Yes, DX systems are generally designed with shorter loop lengths, but this is not primarily due to the conductivity benefit of copper over plastic.
2. Refrigerant in the ground vs methanol/ethanol/glycol/etc in the ground. This also seems like a wash to me – both are unlikely to leak and if they do leak are unlikely to turn your yard into a superfund site. Maybe a conventional system has a very slight edge here because if you want to you can specify a food-grade antifreeze.
3. System cost – this is a tough one since there are so many factors. In terms of equipment I don’t see a lot of difference driving the cost – a DX pump eliminates a heat exchanger but adds a “charge control”. Closed loop systems require one or more pumps and associated plumbing which can really add up for valves, fittings, etc. DX systems obviously tend to use less pipe, but with the price of copper I would imagine that the pipe costs are still higher for DX. DX uses more refrigerant which seems to be going up in price. I think the biggest potential cost difference is in the drilling – if a DX system can get equivalent performance with the bore lengths I’ve seen quoted (and at a smaller diameter) the drilling savings must be substantial. I wouldn’t think there would be much in the way of savings on a horizontal field, though. All in all it’s not surprising that DX is cheaper in some cases and water-based systems are cheaper in others. Too hard to make a generalization here.
4. Installation – Another tough one. Somewhat different skill sets are required – brazing and refrigerant charging for DX, fusion welding (usually), plumbing, and loop purging for closed-loop. I think if the installer for each is skilled and experienced it is another draw. Closed loop systems are DIY-able, though it’s not a good idea for most people to attempt them. Going back to the drilling from what I’ve seen the drilling rigs for DX systems are much less invasive I’m guessing due to the smaller bore required? I guess for a retrofit using a vertical system I’d have to give DX the nod here for this reason.
5. Reliability – I’ve heard lots of horror stories about both types of systems, but if installed correctly both seem very reliable. Eliminating the loop pump and associated plumbing is directionally correct from a reliability standpoint. I think the geothermal industry has a lot to learn in terms of loop field plumbing in general. Pumps tend to be oversized and inefficient and I don’t like the practice of using the loops field as its own expansion tank. It only saves about $100 worth of parts and requires loop pressures to be set much higher than they would otherwise need to be. Bronze pumps should probably be used for longevity since HDPE and PVC are permeable to oxygen, so an iron pump will rust. Maybe one of you guys with field experience can shed some light on specifically what tends to fail on ground loops. I guess I’ll go with DX here as well with the caveat that I think a properly executed closed-loop system will generally be just as reliable.
6. Performance – here’s the big one and I came up with more questions than answers once I started thinking about it. In theory, a DX system should have the edge because as DXers are so fond of saying the refrigerant picks up heat from the ground directly rather than through an intermediate fluid. This should lead to higher evaporating temperatures (I always think in heating mode being in the Northeast) and therefore better efficiencies. I’ll use my system for the sake of argument. My average incoming loop temp in the cold months was in the mid-30s, lets say 35F. The efficiency loss in the water-refrigerant heat exchanger meant that my evaporating temperature was about 21F. The difference between an evaporating temp of 35F and 21F changes the COP from 3.7 to 4.9 at 100F condensing temp for my compressor – that’s pretty damn good.

The other efficiency difference is the elimination of the loop pump. In a properly sized, closed loop system this shouldn’t be a big deal – my loop pump draws less than 4% of the power of the compressor. Given that many closed-loop systems are over-pumped, this may be bigger for an average system.

Now here’s where I get frustrated by the lack of info and case studies available for DX systems. Virtually all the conventional geo companies publish performance specs over a wide range of loop and indoor temps and flows – these are necessary to design the system. I have not been able to find any performance data on the DX systems other than the ARI ratings which are only at a few select conditions. Similarly I haven’t found any case studies where refrigerant temperature was recorded over the course of a season. The literature tends to imply that the refrigerant will be at the undisturbed ground temperature all the time, but that is obviously not the case. The refrigerant temp will vary much as the fluid temp in a closed loop system varies depending on lead, weather, and soil conductivity. Given the dramatically shorter loop lengths being quoted, I assume that DX systems are generally designed to minimize loop length rather than to maximize efficiency. Not that there’s anything wrong with that, but I’d like to see some data agreeing with this or refuting it.

In conclusion, sorry NickB, but I think it really does come down to personal preference and how comfortable you are with the contractors involved. Both systems properly installed should work well. DX systems have a potential inherent efficiency advantage but seem not to exploit it to the fullest in most installations (I’m basing this on the very limited information available), choosing instead to lower install costs with shorter loop lengths. My own preference for now is to stick with conventional systems until I see more data and design information on DX systems. I’m far from the typical consumer, but I want to see the tradeoffs between loop length and efficiency and understand what the performance will be over the course of a season.

Wow, I didn't realize how long this was getting. Time to go to bed!

Wow... my eyes started glazing over while reading this:) Probably more from the lateness of the hour than anything.

My hat goes off to you cnygeo!! You have done an excellent job of adding a lot of clarity to the DX vs WaterLoop discussion. Thank you.

I also have been impressed with the civility of the posters on this board.

cnygeo,

Great Post!

On the availability of DX design info, you can get that at an EarthLinked training. I'm going to send them your post in my efforts (I've been trying) to get them to make it readily available on their website.

They do have that info already. They have (in 5 deg. F. increments) the info for 6 different types of loop installations, showing the difference in efficiencies and capacities when different amounts of loop are installed. You're right. They typically get installed for the least price, choosing the smallest loop possible for the system to work well. That said, there is not a whole lot of efficiency difference between the smallest to largest loop. e.g., the 100' per ton drilled loop is chosen the most. It at 50 deg. ground on a 4 ton has a COP rating of 4.2 when the system is at full capacity. With the horizontal pit loop, that same system has a 4.5 COP. While this is a measurable difference, it's not a huge difference.

Thanks for your post, though.

Nick:

For that decision, I'd need to know what type of COP the open loop system tests at when the outdoor temp is at design temp. I'd personally suggest the system that has a higher efficiency throughout the year.

You can put the numbers into the Elite Audit software and should find that out. Your EarthLinked dealer hopefully can do that for you. If not, his sales rep can. If not, let me know, and I'll get the info from you to do it myself for you.

Keep us informed.

Answers:

#1 sorry no way to answer this question

#4 Yes the return temp can get below 32° F

Observations:

Two slinky trenches with 700' of pipe each is not even close to enough pipe for a 76,000  btu heat pump

Slinkies are 3' wide so I am  not sure how you get it in 2' wide trench.

How do vertical DX systems prevent refrigeration oil from accumulating down in the bottoms of the U-tubes? Basic refrigeration principles suggest the only way to do this is to spec thin enough tubing to keep refrigerant velocity high enough to carry the oil straight up, but the increased velocity would seem to me to reduce efficiency.

This is a pretty basic consideration in the design of refrigeration systems, but I don't know enough to be certain of the answer...

Hi Engineer,

Goto ecrtech.com goto products goto flowcontrols, and that will explain how they do it.