Open loop basics

Discussion in 'Geothermal Loops' started by Shepherd, Jan 6, 2015.

  1. Shepherd

    Shepherd New Member

    Hi all,

    Any info would be very appreciated. We are in the infant stage of this whole geo installation, since our house won't be built until this summer (at the earliest).

    I am currently under the impression that an open-loop system using well water has cheaper start-up costs than installing a closed-loop system, and we just had our well drilled that seems more than adequate for it, but I have a few concerns. I apologize if these are embarrassingly rookie questions.

    My main concerns are what to do with the water after it runs through the geo (seems to me that having to drill a re-injection well would end-up costing much more than just digging a horizontal closed-loop), and what effects water hardness and other well water impurities will having on the life of the geo (I don't yet have any idea what the quality of the water is).

    Thanks very much for any help.
  2. urthbuoy

    urthbuoy Well-Known Member Industry Professional Forum Leader

    I'm biased against open loop except in larger commercial settings. They certainly can be done right, but you really do not end up with any capital savings when they are plumbed right. But they are often plumbed with savings in mind which leads to a bunch of headaches down the road.

    Our area has a history of "my heat pump needs 15gpm" so I'll direct it off my well pump. The very nice thing, is it is an easy concept to grasp and to implement. No real design goes in to it. But then you deal with oversized pumps, air in plumbing, noisy plumbing, and high pressures.

    That beings said, open loop water chemistry certainly has an effect on your system (domestic and heating). This can change over time. And yes, you need some capacity to deal with the very large amount of water volume on the discharge side. This too can be silted up or lead to flooding in crawlspaces, etc.

    But some areas are great for open loop concepts - I'm thinking fractured bedrock with little silt. An area where horizontal would be very expensive to install.
  3. docjenser

    docjenser Well-Known Member Industry Professional Forum Leader

    I too discourage from open systems unless there is a very specific reason for it. Sometimes geology dictates it, or the benefits outweigh the disadvantages, usually in larger systems.
    A closed loop is such a nice controlled environment, it is worth paying for.
  4. waterpirate

    waterpirate Well-Known Member Industry Professional Forum Leader

    I do both. A good indicator would be " does anyone in your immediate locale have a open loop that works well?" Every location has its best form of exchange. The type of exchange is dictated by economics balanced against the expected life span and ease of service. If you look at those 3 things, the right choice for your project will present itself. Hope this helps.
  5. Shepherd

    Shepherd New Member

    Thank you all very much for the expert, helpful replies.

    I talked to a local installer, and, according to him, we have a well that will have enough output for an open loop, but our property has no-where to discharge the water, so we would need to dig an injection well. On the other hand, again according to him, our clay soil is ideal for a closed, horizontal loop. The open loop would be about $8K-9K cheaper, but after drilling an injection well, the costs would be pretty similar.

    So, I am assuming that most of you would opt for the closed-loop, right?

    Thanks again.
  6. waterpirate

    waterpirate Well-Known Member Industry Professional Forum Leader

    If the price differance is that narrow, installing a closed loop is a no brainer in my opinion. Designed properly it will give you years of maintance free service. The loop will outlast your equiptment. I think you have found your answer.
  7. Mark Custis

    Mark Custis Not soon. Industry Professional Forum Leader

    Water runs down hill.

    You could set up the discharge to make ice mountains in the yard.

    I hate winter.

    No creeks or streams down hill?

    Closed loop is better.
    Last edited: Jan 10, 2015
  8. Shepherd

    Shepherd New Member

    Thanks again, guys.

    My only discharge option other than a well would be into the ditch out by the driveway. I'm betting my neighbors down the road wouldn't like the new creek alongside the road.

    Looks like we're probably going with a closed horizontal loop.
  9. Shepherd

    Shepherd New Member

    Hi again.

    Not meaning to argue, because I really have no clue what I'm talking about, but according to the Energy Star website (, most of the heat pumps listed are about one full COP point higher when used in open loop compared to closed loop. I'm assuming that this is because ground water maintains a more consistent temperature year-round than the ground does.

    I'm sure that you guys know this, so I'm assuming that this efficiency increase is still not worth the trade-off?

    Thanks again for all the help.
  10. urthbuoy

    urthbuoy Well-Known Member Industry Professional Forum Leader

    They don't include circulating pumps in these results.

    Your 1-2 hp open loop well pump vs. a 1/8 hp (x2?) circulating pump in a closed loop.
  11. waterpirate

    waterpirate Well-Known Member Industry Professional Forum Leader

    They also do not take the pendulum into the equation. During the shoulder months your entering ewt from the loop will exceed the numbers for the open loop. When you boil it all together, they have the same numbers.
  12. Calladrilling

    Calladrilling Member Industry Professional Forum Leader

    I agree.
    If the price of a open is going to relatively close the price of a installed closed loop, then my choice would be a closed loop.
    Open loops are nice when the water quality is ideal.
  13. Russ

    Russ New Member

    Open loops are asking for problems. Pump motors fail, wells conditions can change and iron manganese tannins and water quality is important. Spoke with someone recently where slightly brackish water was being used throughout his geothermal install - wreaked havoc on his system - go closed loop - more controlled and well worth it now
  14. mtrentw

    mtrentw Active Member Industry Professional Forum Leader

    The one area where I see open loops that makes sense is where you've an artesian well. I think Curt Kinder (engineer) who lives near my folks just south of Jacksonville, FL has more experience in this than many. My dad once knocked the wellhead off with the mower and it reached up a story or more.
  15. engineer

    engineer Well-Known Member Industry Professional Forum Leader

    Closed loop is difficult in FL owing to elevated ground temps (70-75). OTOH we have a sweet aquifer, the Floridan. UB Chris is quite correct, though in calling out pump power as a significant issue with open loop. A poorly designed system can more than eat up the geo savings compared to air source via pumping power. In fact down here it is difficult to make a use case for geo away from beachfront projects where salt air and wind driven sand chew up air source systems.
  16. Mark Custis

    Mark Custis Not soon. Industry Professional Forum Leader

    I just limped up out of the mosquito ridden wilds of Warren County Ohio. I was helping a customer who had spent $20,000.00 not being comfortable. I have never in 66yrs left a job undone. I am looking for an asshole who can add loops to the sheet metal and run the pex. The rest is done.

    I learned the true value of what I know when I could not do the work.

    I chime in because of what happened on this job, not my failed result.

    I close loops. More control. This is open. Not enough water to drink and run the HP in the winter. So someone thought they could move enough BTUH by running the pump and dump through a cistern. Cost $12,000.00 did not help.

    So Steph and I show up with serious mod-con boiler and coils and pipes, and find that both heat pumps are broken. I thought the thing that needed to be done was get what he had going. I did that it cost me three days and re-damaging my left foot. I did not finish my contract, and am now losing money, which I can not afford as disabled/retired doing taxable bit-gigs.

    All you big burly plumber types would be amassed at what a loving 60 year old 125# wife can do in less than a week.

    I am Like McKarther, I will return or send some else.

    My point is this guy spent enough for two sets of closed loop for his home and is freezing. To say nothing of what he sends to Duck Energy.

    Closed the loops, but get someone that know what they are doing not folks that think they know.


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