New Hampshire Ground water temperature drop?

Discussion in 'Maintenance and Troubleshooting' started by ddinnsen, Mar 18, 2021.

  1. ddinnsen

    ddinnsen New Member

    I have been running an open-loop geothermal system in southern NH for 9 years. It has an auxiliary drain set to open when the EWT drops to 47. Until recently the aux drain has never opened, but lately it opens a lot. When the system was installed in the Summer of 2012, the EWT was measured at 54 (which seems too high for NH). I'm pumping less heat this year than the past. I verified the EWT is correct using a second probe. Water is pumped to and from an 800' deep well, and the aux drain dumps into the house perimeter drain. It seems like I may have a problem with my well. Any suggestions for how to diagnose?
     
  2. ChrisJ

    ChrisJ Active Member Forum Leader

    What is the EWT at this time?

    Edit: 47
     
  3. ddinnsen

    ddinnsen New Member

    right now it is 48. I have seen it drop to 43
     
  4. SShaw

    SShaw Active Member Forum Leader

    It's not necessarily a problem. The drain is designed to raise the temperature of the water in the well by allowing warmer water to flow in from the aquifer. So, it's doing what it's intended to do.
     
  5. ddinnsen

    ddinnsen New Member

    I realize that, but, of course, it may also indicate an underlying problem. If my anti-lock brakes started operating routinely, I would check both the driving surface and tread - maybe I need to replace the tires? There is no question that my aux drain circuit, as a sub-system, is operating correctly. The question is, what may have changed to cause the temperature drop? Could something have changed in the well that impedes the discharged cold water at the top from mixing with the deeper water even though the well is capped? There is no significant change in flow rate that the well's potential production. Nor is there any change at all in flow rate for the geothermal system: it is locked at stage one only and operating at a constant 7 GPM.

    Another reason I want to solve this is the Bosch CE061 is tripping its breaker after about 7 minutes of operation in 2nd stage (which is why I have disabled the 2nd stage). I suspect that this is a due to a combination of lower EWT and slightly reduced water flow. When installed, it had 16GPM, now it has 13 GPM. If there has been no change in well production, the 3 GPM drop is all due to the addition of a 1.25" Caleffi balancing valve and two elbows. (This is because I staged the water flow so that it gets 7 GPM on a first stage call, and full flow only on a 2nd stage call, I'll post this as a suggestion in another post once I verify that it works for both heating and cooling. The staging worked great all Summer for cooling.) I'd like to finish addressing the EWT possibility first before replumbing to increase the water flow.
     
  6. SShaw

    SShaw Active Member Forum Leader

    A 43 degree EWT should pose no problem for your system, which appears to be rated to operate at EWTs in the 20s (with antifreeze, of course). A 43 degree EWT should not be a problem, nor trip a circuit breaker.

    You wrote that there has been no change at all in the flow rate of 7 GPM, but you also wrote that the staged pumping hasn't been tested in heating. Have you run the system at 7 GPM in the winters before this year, or was it always running at the 13-16 GPM?

    I don't see why staging water flow would be a problem, but I do see the spec sheet for the CE061 shows 14 GPM for both stage 1 and stage 2.
     
  7. ddinnsen

    ddinnsen New Member

    This is an open loop running on well water, so it does have danger of freezing up. I have only run the system with staged waterflow this winter, prior to that it probably ran at 16 GPM (but with no way to measure the flow).

    I think it will be more helpful to the forum to discuss staging design and the over current issue in a separate post, but clearly 13 GPM is less than 14 GPM and could be a problem - especially when the EWT is low. Bosch does not want to get involved in stages water flow, so they offer the same spec for both stages, but 7 GPM is actually what is needed.
     

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