"Shallow rock" affects vertical loop's capacity to heat?

Discussion in 'Vertical and Horizontal Loops' started by Tamar, Dec 12, 2013.

  1. Tamar

    Tamar Member Forum Leader

    For my own education, if on a project you were expecting to hit bedrock at 147 ft, and instead ran into what they report they ran into (in attachment), would that (or how would that) have changed your plan or recommendation on what the loop should consist of? I'm trying to figure out if they ignored important information that they gained access to when drilling, or if they are just going back now and creating this excuse for why the system is underperforming....
  2. Calladrilling

    Calladrilling Member Industry Professional Forum Leader

    I agree that load not equipment dictates loop field size.
    But only to a certain extent.... If the load was incorrect then all goes out the window.
    If the loopfield can not handle the load, then the field is too small... It's really that simple.
    150'/ton with a drill record I'm seeing would be a lot to ask for. I think the .96 recorded on the drill record is pretty close to accurate.
  3. docjenser

    docjenser Well-Known Member Industry Professional Forum Leader

    There are 2 issues here:
    1) The company now says that a 98% load loopfield is not possible and wants to install geo with heavy gas backup, similar to what she now already has, and what has been a completely mis-designed system. She paid a lot to get off gas, and now they want to have 3 tons of geo running with the rest of the load provided by a boiler. The explanation is that the rock is "too shallow" and they are trying to get out of this by giving those kind of BS answers.

    2) While the 67% statement comes from a manual J calculation (e.g.guesstimate), which already assumes a safety factor, to which the engineer added another 15% safety factor, and declared the loopfield too small. Her actual previous gas consumptions data over the last years match with the weather data (e.g. real data) suggests an actual heatloss around 70,000 BTU/h at design temperature. While she has 8 tons of equipment installed, she does not have an 8 ton load, so please do not state here that her loop field is too small and does not support her load without knowing the facts!

    Tamar, they are giving you a BS excuse why the system is not performing. At the end of the day, they are the contractor, and they must ensure performance. They cannot say the loopfield is too small, sorry, now go back to gas. They took your money for it, and were incompetent in the design and installation. There is no reason why they could not have drilled down to 400 ft instead of 200ft if the issue would have been that there is not enough room and her lot is too small.
  4. Tamar

    Tamar Member Forum Leader

    I found this information on the web, do experts here agree with it? It seems to be saying the opposite of what my installer is saying, if I'm reading it right.

    "Soil type affects the necessary loop field size because different types of soil have different abilities to absorb energy. Extremely dense soils, such as rock and clay, have the ability to hold a great deal of heat and can therefore transfer more heat. Sandy soils absorb far less heat and therefore require a larger loop field. As a general rule of thumb, the drier the ground the larger the loop field required."

    reference: http://www.geothermalgenius.org/how-it-works/sizing-a-geothermal-heat-pump-system-design.html
  5. docjenser

    docjenser Well-Known Member Industry Professional Forum Leader

    The denser the rock, the better it works for the purpose of conductivity and as a loopfield. So the more rock they have the better.

    If one does not find what they expect to find then you need to redesign to make thinks works. If they really think the loopfield cannot be established to support what they think is needed, why did they continue with the install and took your money? Why did they not fix the design. For example by drilling deeper. Putting in 300ft boreholes would have increased the capacity by 50%. If within their math, that would have brought up the capacity from 67% to 100%. What would that have to do with the lot size and them now saying that your lot is not big enough?

    The funny thing is that they appear to be off on their load calculations, at least their consulting engineer is. In reality your load is much less, thus I don't see any reason why your loopfield should not support your 70,000 BTU/H max load.

    They have given nothing but BS in the past, and continue to do so. In this case to get he district attorney off their back.
  6. DavidCraig

    DavidCraig Member


    Do you know your EWT? [ If not, please measure it and let us know. ]

    If your EWT is fine (say >30° F), then your system should perform without the gas assistance.

    The next would be the LWT. Knowing EWT and LWT would let us know if loop flow rate is ok (another possible issue).

    In the end, what constitutes a good loop design comes down to EWT in the dead of winter. Whether 500 ft or 5000 ft of pipe, in clay, sand, or potatoes, it is the temp of the water you get from the ground that matters.


    While many posts on the forum seem focused on loop design, a very important issue is load temperature. Since on paper your loop setup seems adequate, then the problem may be elsewhere.

    For water-to-water systems (your 3 ton), to achieve 3+ COP your temperature should not be much above 100° F. If set to 120° F, for example, the efficiency will be significantly lower and the total heat will be somewhat lower. If >120° F, then the total heat will be significantly lower - so the backup would be needed.

    With water-to-air, the air flow would be your 'load temp'. You mentioned a high velocity air handler. Perhaps it isn't getting enough air flow. The amount of air flow needed for a gas system can be significantly less then needed for geothermal. If the flow isn't there, then the system is choked up. What is the temperature of the air coming out of your registers?

    The 67% verses 98% performances discussed above could easily be the equipment inside the house not set up properly. Retrofitting an 1898 Victorian is certainly possible, but it usually takes more work than new construction.
    Last edited: Dec 19, 2013
  7. ChrisJ

    ChrisJ Active Member Forum Leader

  8. Tamar

    Tamar Member Forum Leader

    Welcome, David! Chris, thanks for posting the links; David will see I've had lots of good advice about the issues inside our house. Does anyone have an opinion on this newest piece of info from the installer; that they want to remove our high temp unit and replace it with a high efficiency boiler because of the shallow rock on our lot (which apparently must have been a surprise to them....)?
  9. DavidCraig

    DavidCraig Member

    Wow, lots to sort through. Was going to ask what your therms were in the Januarys prior to installing Geo. But $200 for Feb (gas) verse $615 for Dec (new system) kind of says it all. If a home can be heated for $200 / month, it can be hard to justify Geo in the first place. Let alone a $60,000 system.

    Looks like a lot of bases have been covered. Sorry for your distressing situation.
  10. docjenser

    docjenser Well-Known Member Industry Professional Forum Leader

    Didn't you have gas before, and you paid a lot to get rid of it? Now they want you to go back to gas? I don't get it. Lets put an end to this: They designed your system, entered into a contract, took your money, and now they say that their design cannot work?!
    OK, let them give you your money back and move on.
    Last edited: Dec 19, 2013
  11. Calladrilling

    Calladrilling Member Industry Professional Forum Leader

    That's is exactly the avenue I would take too. They do not seem to willing or able to repair what you have installed.
  12. Tamar

    Tamar Member Forum Leader

    I will be responding to their response to Angie's List (at the top of this thread) on Monday. I had requested my money back in the initial case. Will ask again, and will keep asking....
  13. waterpirate

    waterpirate Well-Known Member Industry Professional Forum Leader

    I will give any contractor/ busines partner/customer/vendor/ the opportunity to make it right. I ask the same grace from them. After exausting any and all options at resolution to make all parties happy, you are left with only one. The legal option, my least favorite.
  14. Tamar

    Tamar Member Forum Leader

    I know I've taken a lot of everyone's time, and I just want to say thanks once more. I'm taking every piece of advice to heart and eventually will have a better geo system because I understand so much more than I did at the beginning of this adventure.

    I am moving forward with a plan of attack, which is how I got the written "offer" to remove our hi-temp W2W and accept gas for 1/3 of our heat load.

    I've filed a dispute on Angie's List suggesting the resolution would be for the installer to refund our money, and after 2 weeks got the response above (plus some other smoke).
    I've filed a complaint with the Minnesota Attorney General, and I suspect/hope there is something in the mail for me regarding that complaint.
    I've contacted MNGHPA and suggested they stop listing this installer under their "find a pro" section as "one of the good guys"
    Next steps....BBB and binding arbitration, unless they admit that they are ill-equipped to resolve the issue and they agree to my request for a refund. I continue to research and ask questions mostly so that I can field any argument that comes up during arbitration, but also to make sure that I'm armed to make the best decisions going forward.
    Last edited: Dec 21, 2013
  15. Tamar

    Tamar Member Forum Leader

    We have been home about an hour. We switched over from emergency heat (gas boiler only) set at 66 degrees, to "regular" call for heat at 69 degrees.

    The split is running, the W2W has the breaker pulled.

    EWT to the split is 47, LWT from the split is 39.

    The gas just kicked back on, as I believe it is set to do if a call for heat isn't satisfied in 45 minutes.
    Last edited: Dec 20, 2013
  16. DavidCraig

    DavidCraig Member

    EWT of 47 in December in Minissota ... the loop is not overtaxed. Delta of 8 degrees is fine - with 47 EWT the furnace should 'move' plenty of heat ... so where is the heat going? 5 tons is 60,000 btuh!

    What happens if you just shut down the gas furnace for a couple days? -- what temp does your home level at after a day or so?
  17. Tamar

    Tamar Member Forum Leader

    Maybe the experts will chime in here, but I am guessing we are not getting the full 60K btuh because the SpacePak is short on return air and has a poorly designed supply air configuration, and also because the loop in the house is undersized which introduces unnecessary restriction.

    I don't believe that with our current control set up we have the option to shut down the gas "boiler" which is actually a 100k btu water heater (Phoenix).
  18. Mark Custis

    Mark Custis Not soon. Industry Professional Forum Leader


    Just turn off the gas to the boiler.

    I agree with David and Joe and Doc, the loop field will carry the house load. I do not like the way your system is piped as I mentioned before in the other thread.

    With Doc's take on the radiators acting like a buffering tank, I think you are trying to heat with the wrong machine. I would have you try running the w 2 w machine to the radiators. Then use the unico system when the radiators can not keep up.

    You can contact me if you need help with the controls.

  19. docjenser

    docjenser Well-Known Member Industry Professional Forum Leader

    EWT in a geosystem which did not run (Tamar had the boiler running) means nothing and should not be used to judge if the loop if capable to work for her or not. 8F delta T is not that great either, given that there are 3 circulation pipes running to overcome the flow restrictions designed and installed in the system. Also the delta t will go up indicating even lesser flow if you have the second heatpump (W2W) running at the same time. It is lesser an issue with the loopfield but indoor flow restrictions, as far as we have been able to tell from our remote locations.
  20. Tamar

    Tamar Member Forum Leader

    Here is pressure drop information from Dec 11 (outside temp was hovering around 0 if that makes any difference). I am unclear on the implication of low numbers for pressure drop. These readings were taken with the loop pumps running but the compressors not running:

    W2W: 25.5 in, 24.5 out
    Split: 27 in, 25.5 out

    These numbers indicate a pressure drop that is less than when the readings were last taken in mid November (at that point the W2W had a pressure drop of 2.5 and the split had a pressure drop of 3, with an EWT of 45 degrees)

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