Questions I should be asking my well driller

Discussion in 'General Discussions' started by JRBGEO, Jan 14, 2009.


    JRBGEO Member Forum Leader

    Hi I am in the process of doing a proper Heat loss / Heat load analysis for my house to correct a sloppy GEO install done at my house in Connecticut this October. The installer gave me only 2 boreholes at 225 feet for a 4 Ton Envision unit from WF. The EWT for my system is in the mid 20's right now.

    As I go through this process I want to make sure I am asking the right questions to my well driller. Should I be asking for a design plan of the loops? Should I be specifying what EWT I want to see when all is set and done? From feedback I have had from other members in this forum I understand that all the geo wells have to be the same depth, so I will need another 225 borehole, maybe two boreholes. The casing has to be of the same diameter as well the the black poly tubing inside the wells. There are also issues related to the "Reynolds number" or turbulence that I have to address. I guess that I am looking for some checklist of what the proper questions should be. I spent a lot of $$$ for this system and now I am being forced to spend some more to correct a bad situation. Any feedback would be appreaciated. Thanks!
  2. Mark Custis

    Mark Custis Not soon. Industry Professional Forum Leader

    Before I drilled anymore holes

    I would look at two things:

    Size of the pump(s) this is not a one size fits all situation.

    Size or ID of the tubing.

    I would try to lower the speed of the flow to the loops. Have you had any "lockouts" and what was the fault code?

    JRBGEO Member Forum Leader

    I have had multiple "water flow" lockouts they have the freeze limit set at 15 F and the system has been running on Environol since Friday. I think the heat pump was sized correctly (4 tons)...we are getting 68-70 F with not problems sice last Friday. The problem is that we are accepting a low EWT....mid 20's F and that degrades system performace and increases my utility bills. I have to add one more borehole at a minimum, maybe two. If I knew what questions to ask at least I can tell who is BS'ing me and who is not. Thanks!
  4. Mark Custis

    Mark Custis Not soon. Industry Professional Forum Leader

    The heat pump

    sees temperature not water flow as the issue.

    Given the length of the loops but not the pipe size it is difficult to determine the number of BTU we can move through the pipe.

    I am saying if we slowed the flow the loops could pick up more heat from the ground.

    There is the possibility of there being air still in the loop. I pressurize all of my loop systems and equip them with a pressure tank, micro bubbler air eliminator and an auto fill device. The auto fill stays off after commissioning.
  5. Palace GeoThermal

    Palace GeoThermal Well-Known Member Industry Professional Forum Leader

    Are your wells cased with the loop pipe inside the casing?

    If so this would cause problems by interfering with the heat transfer from the ground to the loop.

    Do not lower the flow through the loops, this will decrease the flow needed for good turbulence in the loops.

    Your purpose in doing this is to raise your EWT, so I would focus on that part of it.

    I would ask then for a loop design report that shows what the minimum EWT will be with one extra loop and two extra loops.

    JRBGEO Member Forum Leader

    I have about 40-60 feet of casing (6 ") diameter on each well (where it is going through sand)....after that there is no casing as the borehole keeps it's integrity when it is going through bedrock.

    They tried slowing the flow in the Circulator pump at one point in time but set it back to what it used to be after they realized that was not an issue. Loops have been flushed 3 times already so I don't think that is an issue either. Again when you are running a 4 Ton envision on just 450 feet of borehole there is only so much you can do. Ideally they should have given me 200 feet per ton - 800 total for the system to run efficiently.

    I agree with this:

    I just wonder if they can try to "blow smoke" by me and tell me: "Ohh we don't have a way to predict the one can....blah..blah...blah..."
  7. Palace GeoThermal

    Palace GeoThermal Well-Known Member Industry Professional Forum Leader

    The 40 - 60' feet of casing further reduces the ability of your loop to provide you the heat needed.

    Leaving casing in the ground is not an accepted practice.

    JRBGEO Member Forum Leader

    I think this is total for both boreholes. I believe is 30 feet of casing per borehole....

    Are there any guidelines per state as to what acceptable EWT would be....I have been told the average temperatue in CT is 50 F (add all the daily temps and divide by 365). So if your avg temp is 50 F that is what your ground temp will be....true or not?

    So basically out of the 450 I have 60 feet that are not contributing to the heat transfer right?

    Who will be responsible for addressing the turbulence issue? The well driller or HVAC contractor?
  9. engineer

    engineer Well-Known Member Industry Professional Forum Leader

    Depends upon who has ultimate design responsibility

    A good place to start would be with who pulled the permit to install the system - that individual bears final responsibility for a functioning system.

    HVAC contractor may have subbed out the well drilling only, or the whole loop system (design, drill, plumb, fill, flush, pumps) Doesn't matter - HVAC contractor is primary.

    OTOH if the homeowner contracted with HVAC to provide just the airside installation and promised adequate flow and adequate loop length via an independent well driller, that would be different, assuming it was in writing. I doubt that applies in your case.

    Slowing flow will NOT cause more heat to be transferred from the ground. EWT might temporarily rise, but the lower flow would quickly cause lower LWT (higher delta-T across heat pump) As that lower LWT water reentered and completed a pass through the loop it would result in lower EWT and LESS total heat from the loop.

    It gets worse if loop flow drops below that necessary to maintain turbulent flow. Without adequate turbulence heat transfer into loop fluid drops even further.

    Think of a car heater - running fan on lowest setting results in highest temp at air outlet, but NOT the max heat from the heater - for that we crank the blower up a couple notches - more air a bit less hot gets us warmer faster.
  10. JRBGEO

    JRBGEO Member Forum Leader

    The HVAC contractor from WF subbed the drilling work to a local well driller contractor. They pulled a permit from our town and I have a copy of the completion report as well. My sales contract states "system is tested and set to operate at peak efficiency"....obviously it is not when you have an EWT in the mid 20's and probably getting lower as the artic cold front heads to CT today and the rest of the week...Can you really blame the well drillers if the HVAC contractor tells them to drill 450'? Probably not...they are just following orders...
  11. JRBGEO

    JRBGEO Member Forum Leader

    Another question along these lines....the loop installer and the HVAC contractor are going to tell me: "Well the reason your loops are cold is because they are brand have to go through a summer to really determine what the proper EWT is? Should I buy this line of thought?
  12. Palace GeoThermal

    Palace GeoThermal Well-Known Member Industry Professional Forum Leader

    There is design software that will predict EWT's over the season. Predict is the operative word there.

    I know of some installers who give a guarantee that EWT will not fall below a certain point.

    Your EWT will never match the ground temp, this is impossible.

    Most systems are designed so that the lowest EWT will be 30°.

    By adding more loop, you can get a higher minimum, but the benefit does not justify the cost.

    It is true that your EWT in the winter will be higher after a cooling season has passed. The actual increase is debatable, but there will be some increase.

    Your HVAC guy is the one who should make sure the flow produces turbulence.

    I hope i answered all the questions here
  13. JRBGEO

    JRBGEO Member Forum Leader

    Yes you did. Thanks again.
  14. waterpirate

    waterpirate Well-Known Member Industry Professional Forum Leader

    well casing

    It is quite a common practice and the law in many states. The overburden must be cased off and the casing set 3 feet into the bedrock to prevent contamination present in the overburden from leaching into the aquifer.

    That being said it is a design factor that simply has to be accounted for.

    My question would be the thermal link. Hard rock boreholes have verry poor conductivity unless the entire borehole is grouted, providing the "link" to surrounding strata.
  15. Palace GeoThermal

    Palace GeoThermal Well-Known Member Industry Professional Forum Leader

    Thanks for the info
  16. waterpirate

    waterpirate Well-Known Member Industry Professional Forum Leader

    questions for the welldriller

    I would ask the folllowing:

    Have you drilled closed loops before in my area?

    If so what was the average depth per ton of load that you drilled?

    What did you base your footage per ton on?

    Do you grout the entire borehole from bottom to top to provide a "link"

    Do you have a list of hvac contractors that you work with frequently?

    I am allways happy to dispense this information. If the driller you have contacted is not. Move on to another driller.
  17. Ok, I will bite. What would slowing the water flow do? How could this possibly help?
  18. Mark Custis

    Mark Custis Not soon. Industry Professional Forum Leader

    I do

    hydronics all the time.

    I thought given the cost of making holes in the ground, it might be time to look at flow.

    I do not see pump curve numbers here.

    A tuned system can make the heat pump happy.
  19. OK, But how would slowing down the loop flow help?

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