Tennessee New Geothermal Not keeping up/High Cost

Discussion in 'Maintenance and Troubleshooting' started by gorilla33, Jul 30, 2020.

  1. gorilla33

    gorilla33 Member

    Yes the Geo pump is on, the PEX from the GEO to the standby tank is very warm. I just cant figure out how the recirc pump is causing the WH to run 50% of the time.
     
  2. gorilla33

    gorilla33 Member

    Here is my setup after studying all of the routing.
     

    Attached Files:

  3. SShaw

    SShaw Member

    That's how I envisioned it from the photo.

    The piping between the buffer tank and the geo is supposed to be copper.
    The piping between the geo and buffer tank is supposed to be insulated. You will lose heat and efficiency this way, and add to the cooling load.
    The hot line from the geo into the buffer tank is recommended to go into the bottom of the buffer tank. You might lose a little effectiveness the way it's setup.
    The diagram ChrisJ posted shows several check valves. I don't know if you have those, but without them, it's possible the water may flow in unintended directions.

    Hot water recirculating through your home's piping will lose heat and cause the WH to run more often. Who knows whether that can account for 50% run time, but constant recirculators are known to be huge energy wasters. It looks like you have no insulation on any of your piping, so you are probably operating near a worst case scenario.

    With your recirc system running 24/7 it could be wasting $100 - $200 per month, which is likely more than your heat pump uses to cool the house. You should be able to estimate the waste with your Sense system.
     
  4. gorilla33

    gorilla33 Member

    Plumber just left and we did a few different test with nothing conclusive. The plan is tonight before bed, I am going to close the isolation valve between the 2 tanks. This is to attempt to rule out that the re-circulator is pushing flow in the wrong direction. If the WH cycling goes away, its a plumbing issue between the tanks and Geo. If they continue, it something with the WH itself.
     
  5. SShaw

    SShaw Member

    A better plan would be to valve-off the recirculator loop and kill the pump, then see what that does to the WH cycling.

    A 24/7 recirculator is a well-known energy hog. Pumping 130-degree water from your insulated WH out through your uninsulated pipes necessarily will cause the WH to come on more often, and it will cost money. See attached for an analysis of the costs.

    Check valves prevent water from going in the wrong direction. See ChrisJ's diagram for where to place the valves. The plumber could have added the valves for you while he was there.
     

    Attached Files:

  6. gorilla33

    gorilla33 Member

    Understand on the pump and I may add a timer to it. Also understand he could have added the check valves but we wanted to change one thing at a time to find the main issue. I will ultimately add the check valves. I’ll likely also have him swap the goes in/goes out from the geo too. I think he was a little more reluctant to move the recirc location.
     
  7. ChrisJ

    ChrisJ Active Member Forum Leader

    I think when hot water is being circulated by the DSH (desuperheater aka hot water generator) the refrigerant is actually picking up heat from the water because the water is hotter then the refrigerant, hence putting heat into the refrigerant which adds heat to the loop.
     
  8. gorilla33

    gorilla33 Member

    What would be causing this? I to have been wondering is some how the desuperheater is causing my Geo loop to heat up, but i don't understand it.

    I think my test below demonstrates that I have an issue, even if the Geo unit didn't exist.

    Of note, I isolated the communication between the buffer tank and the energized tank last night. This provided no change to the performance of the WH. It came on and off all night long with no water being used. This leads me to believe that the re-circulation is losing that much heat and causing the WH to energize frequently. My understanding is that my setup for recirc is very common, but I cant imagine that it is working appropriately. Here is the data:
    1:12AM-1:23AM On
    1:43AM-1:55AM On
    2:19AM-2:30AM On
    2:50AM-3:00AM On
    3:21AM-3:32 AM On
    3:53AM-4:04AM On
    4:45AM-4:36AM On
    4:59AM-5:11AM On
    5:34AM-5:45AM On
    6:06AM-6:17AM On

    At this rate, I am using 1238kWhrs of Electricity/Month to heat water. And this is the rate when we aren't even using water. Factor in usage and i'd it goes even higher.
     
    Last edited: Aug 6, 2020
  9. Deuce

    Deuce Member

    I have a hot water recirculating pump that is thermostatically controlled. I also insulated my hot water recirculating loop. I have very low energy bills.
     
  10. gorilla33

    gorilla33 Member

    Can you elaborate on the thermostat controlled and the insulation used?
     
  11. Deuce

    Deuce Member

    I originally had one with a timer and had my plumber change out the timer with this one that has a coupling that goes around the hot water pipe leaving my water heater that feeds the loop. I think the thermostat was under $20.
     
  12. gorilla33

    gorilla33 Member

    what type of insulation did you use?
     
  13. ChrisJ

    ChrisJ Active Member Forum Leader

  14. gorilla33

    gorilla33 Member

  15. Deuce

    Deuce Member

    Black foam pipe insulation linked to above.
     
  16. gorilla33

    gorilla33 Member

    @ChrisJ This seems reasonable. What is the solution to this?
     
  17. gorilla33

    gorilla33 Member

    Now that I know what one my main energy users is and it is not related to the geo unit, I need to get my thread back to its original intent. That is the unit struggles to maintain setpoint, but mostly is at this point. What I am curious of now is some of the energy use I see others reporting on here. For instance @SShaw said you used 420kwh for the month of July. I use that in a week.

    Is my unit running that much more than everyone else’s or is it taking more electrical usage for my unit to operate?
     
  18. ChrisJ

    ChrisJ Active Member Forum Leader

    One of the first threads I started on here was about plumbing. A member named Mark Custis (RIP) told me water is Lazy, without check valves it does what it wants, so one of the first things to do Is fix the plumbing.

    If I had a recirculation loop I would try a occupy sensor, motion detector in bathroom furthest from the water heater.
     
    waterpirate likes this.
  19. SShaw

    SShaw Member

    The SM060 will not run the DSH water pump unless the refrigerant is significantly hotter than the water in the buffer tank. So, this will not happen unless water is flowing when it's not supposed to. Check valves should help prevent that.

    Here in VA, 1,238 kWh would cost about $175. So, your experiment confirmed what I wrote Wednesday: "With your recirc system running 24/7 it could be wasting $100 - $200 per month," and, "It looks like you have no insulation on any of your piping, so you are probably operating near a worst case scenario."

    If your recirc loop is wasting 1,238 kWh per month, that means it's dumping 5,900 BTUs/hr of heat into your house. That's heat that your AC must remove. That adds more than 10% to your peak cooling load.

    As I suggested already, valve-off the recirc loop and kill the recirc pump. You should also insulate the piping between your geo unit and buffer tank. Do those steps and see what the water heater usage is. With the recirc pump OFF and the hot water generator pump ON, the WH usage should be very small, even when using hot water. Your AC should maintain set point better as well.
     
  20. gorilla33

    gorilla33 Member

    I agree with your assessment and I have some thing in motion to address. I don’t know if it matters, but 90% of the recirc loop is routed through my floor trusses in the basement, so it’s pretty easily accessible. There is no insulation between the main level floor and the basement, so I’d assume that heat transfer comes through the floor, although there is 2 feet of air gap between the pipes and the sub floor.

    step1-put recirculating pump on a smart plug and schedule it’s run times. It will run very minimally for morning and night shower time. This is first because it’s the easiest.

    step2-insulate recirc line and geo loop(I’m also going to swap the goes in and goes out on the geo loop to flow from bottom to top of tank, and install the appropriate check valves).

    Step3-Because my upstairs continues to be the major issue my HVAC contractor is planning to increase my return size from the upstairs zone.

    curiosity question-how much energy(wattage)does a traditional 5 ton unit use when running? Is it more than my geo uses?
     

Share This Page