Why doesn\'t everyone go with Open Loops?

Discussion in 'Open Loop' started by eisensms, Jan 16, 2009.

  1. eisensms

    eisensms Member

    It appears that open loops are more efficient because they have a constant supply of unadulterated water at a constant temperature. They can extract considerably more heat from the water (or put considerably more heat into the water in chilling mode) because they don’t have to be concerned about the water synchronizing back to a desired temperature when it comes back to the heatpump. Since, they require far less volume of water, less water pressure, and can run with colder supply water when necessary, I don't
    see why they wouldn't be the preferred first choice. Many of the problems which I have read about in this forum seem to be related to Closed Loops.
  2. urthbuoy

    urthbuoy Well-Known Member Industry Professional Forum Leader

    Open Loops

    • Not everyone has a source of water or a place to dispose of it.[/*:m:t6spthtj]
    • They require more maintenance[/*:m:t6spthtj]
    • Water may not be suitable (temperature, hardness) or in the volumes required.[/*:m:t6spthtj]
    • No freeze protection (not an issue with design)[/*:m:t6spthtj]
    • Permit limitations[/*:m:t6spthtj]
  3. engineer

    engineer Well-Known Member Industry Professional Forum Leader

    All that urthbuoy said and

    Well pump power may be much higher. Unit needs water at 5 psi or so. Supplying it with well water at 40 or so from deep down may use much more power than circulating closed loop water.
  4. waterpirate

    waterpirate Well-Known Member Industry Professional Forum Leader


    An open loop can run on aproximately half the volume of water is true. But with an open loop you pump it and throw it away. With a closed loop you recirculate the same volume.

    Because you only circulate the water, less energy is consumed. A typical circulator pump is 1/25 of a hp. Volume of water circulated is a function of feet of head vs. friction loss.

    In a well designed loop field the water does not reset to to the beginning temp. It slowly cools as the winter continues, giving you exceptional efficency in the early summer when the ewt is lower than normal, over the summer you build heat in the field and get higher than normal ewt for the fall = higher eficency.
    We call these the shoulder months.

    Any time you do a open loop you can not garauntee the results for an extended period of time. ie the aquifer is a living thing, it gives and rejects on it's terms not ours.

    Hope this clears it up
  5. Looby

    Looby Member Forum Leader

    Reliability & low maintenance! I have lots of water, a high water table (less
    than 10 feet below the surface), and a handy stream that could be used for
    discharge -- but after weighing all the factors, I decided to go closed loop.

    The big concern is water quality -- pH, hardness, suspended solids, iron, etc.
    that can cause long-term reliability problems.

    Before going open loop, be sure to have your water quality tested thoroughly,
    and be very conservitave regarding the yield of the source well and capacity
    of the discharge location. Also, pony-up for the copper-nickel heat exchanger

    ...Murphy was an optimist,

  6. dbelisle

    dbelisle New Member

    Open loops are very popular here in the North East ... You don't have to
    go down very far and your into Granite and most of the time there is plenty of water.....

    The down side to that it is expensive to drill through granite.....
    and the quality of water could also be a problem ......

    There can be a lot on minerals or bacterial iron in the water that could
    give you higher maintenance cost of the system.....

    But if your going to drill a water well for your domestic anyway and understand there could be have higher maintenance cost it makes a lot of sense......

    I have open loop at my house....

    Dave in NH
  7. eisensms

    eisensms Member

    Problems with closed loops

    Waterpirate writes:
    "It slowly cools as the winter continues, giving you exceptional efficiency in the early summer when the ewt is lower than normal, over the summer you build heat in the field and get higher than normal ewt for the fall = higher efficiency."

    Could that be stated another way?
    Over the summer, as outdoor temperatures get higher and higher, it
    gets harder and harder to cool your house due to the heat buildup in
    the closed loop, where during the winter, it becomes more and more difficult to heat your house as the loop becomes colder and colder?
    Moreover, it is -25 here right now, so I doubt any Geo unit can heat
    the house in really severe winter weather, without resorting to
    electrical resistance heating.

    I am not sure that I need exceptional cooling in the early summer when
    the nights are still cool, unlike in late August when the nights are sweltering. Moreover, I would think if I can circulate 50 degree EWT,
    I should be able to cool my hose without running the heat pump compressor.

    For me it is a huge decision on whether to go open or closed loop.
    There is a lot more expense involved in digging 450 feet of vertical loop
    for a 3 ton system, versus me digging one 100 foot water well. I understand that there me be more ongoing pumping cost with the open loop.

    Since I really don't know which way to go, I will end up trusting someone
    who I feel is the most knowledgable.
  8. Looby

    Looby Member Forum Leader

    An adequately large geo unit (open or closed loop) can heat anything in any
    kind of weather (same as any other heat source). However, it's not a design
    flaw if the system needs an electrical resistance "assist" on the coldest few
    days of the year -- it's good engineering. An oversized system costs more to
    install and more to operate on a year-round basis.

    BTW, although there's no argument that open loop is "more efficient," the
    penalty for closed loop isn't all that large. An Envision 038 running closed
    loop at an EWT in the mid 30's has a cop of about 4.1; the same system
    running open loop with an EWT in the low 50's has a COP of about 4.6.


  9. Raye

    Raye New Member

    I've only had my open loop system for a couple months now,but at the
    -20 temps we have had here in ohio my backup heat has never came on.I know people who have had open loop systems for 20 years and have never had any of the problems mentioned here with them.It's like a guy who only likes fords cutting down anyone with a chevy.
  10. Mark Custis

    Mark Custis Not soon. Industry Professional Forum Leader

    Folks in Ohio

    tend to think water is limitless.
  11. TechGromit

    TechGromit Member

    What the hell are you talking about? An Open Loop pump and dump system the water is returned to the ground, even without a return well the amount of water being lost to evaporation is minimal. You talk as if an open loop is going to suck up all the aquifers water leaving it dry.
  12. gabby

    gabby Member Industry Professional Forum Leader

    We have a lot of lakes and ponds which would make one think water will never be a problem. The fact is no area is safe from a drought, or overpopulation in a specific area where water resources get strained to the point of rationing. This could be due to a concentration of homes and families or a process that is water dependent (water bottling plant).
  13. Palace GeoThermal

    Palace GeoThermal Well-Known Member Industry Professional Forum Leader

    Out here in the west, water is scarce. I have never even seen an open loop, I probably never will.
  14. Mark Custis

    Mark Custis Not soon. Industry Professional Forum Leader


    I get the TX ground temp thing. Thanks
  15. Mark Custis

    Mark Custis Not soon. Industry Professional Forum Leader


    Yes it could happen that they are all sucked dry.

    Sorry to offend you but, Ohio thinks it has lots of water, now.
  16. sunnyflies

    sunnyflies Member Forum Leader

    My area has a heavy concentration of iron in our water. I am thinking that a closed loop system might make more sense for me to prevent a build up of iron and minerals from clogging up the machinery. I am searching this forum for more info about hard water problems and geo systems.
  17. Mark Custis

    Mark Custis Not soon. Industry Professional Forum Leader


    my guess is the red stuff out of your discharge is yuck, or iron bacteria.
  18. elifino

    elifino New Member

    Reasonable Cost ?

    We live on country acreage in Alvin, Texas.We are going with a Geothermal, open loop, 4 ton system. The well has been drilled, lines run to the Barndo, pressure tank installed and the discharge will be to our pond.The problem I have is ... what is a reasonable price to pay for the remaining parts of the 4 ton system? Ballpark, all in #'s I have seen run anything from $2,500 - $5,000 / ton. My first quote was for $26,500. ( over 6k per ton! ). I asked the contractor to come out and he saw I had the well + already in. He dropped the price to $21,500. The well, tank & lines cost me $8,000 and I'm told that was a good price for that. I was expecting a quote in the $12 - 14k range to finish installing the unit and ductwork. I certainly want to go with a knowledgable, reliable, reputable installer but I don't want to get skinned either.
    Conventional system quote = $7,000. Twice that seems reasonable but 3 times ?
    Any help .... advice ... comments ... would be greatly appreciated.

  19. Cost for 4 ton geo unit on open well

    The last customer I had two weeks ago in Tomball Texas had an existing well and 6 acre pond. I installed top of the line Waterfurnace for him @ $12000.

    www.alliedairtexas.com for info.
  20. Palace GeoThermal

    Palace GeoThermal Well-Known Member Industry Professional Forum Leader

    Hey allied...

    good info.

    I clicked on the link to your website and this showed up:

    Directory Listing Denied

    This Virtual Directory does not allow contents to be listed.

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