Tennessee New Geothermal Not keeping up/High Cost

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

  1. gorilla33

    gorilla33 Member

    I'm with you now. Thank you for the explanation. Sounds like the Sense Energy might be the right solution to my problem. The remaining portion of electrical usage attributed to the cost to cool my home seems more reasonable. Hopefully the Sense Energy monitor can help me figure out what's going on. I can't imagine what would be using that amount of electricity. Brand new home, LED bulbs, Gas Range, "free" hot water from the geo.

    I don't have day by day breakdown for earlier months before i was in "cooling" mode, but i do know my monthly usage for January, February, March time. Could that data be further used to validate this "base load" of usage?
     
  2. SShaw

    SShaw Member

    Yes. You can use the regression tool on degreedays to estimate heating and cooling, and you can do it by month, week, or day. You'd need to read the instructions to see if you can mix daily and monthly data, but you probably can.

    Keep in mind that if you had some problem with your geo that was causing high usage regardless of the outside temp, the degree day analysis wouldn't be able to separate that out. You could tell that by doing the basic efficiency and power measurements I mentioned already. You can download the "submittal data" for your unit and look up the power usage to compare against actual consumption of the running system.

    Looks like the SM060 uses about 4.5 kWh in high cooling with a 90-deg EWT. If it ran on high for 12-hours per day, that would be about 1,600 kWh per month, which I believe is somewhat consistent with the degree day analysis.

    I've looked at energy monitors. One should help you figure out what's using the power. I will likely buy the eGauge when I get around to buying one.
     
  3. gorilla33

    gorilla33 Member

    Looking back at my usage on a monthly basis and doing a regression from the aforementioned website, I get a baseload of 72kWh/day. Obviously, with less data points(6 vs 62), this is a less accurate prediction, but stills shows I have a significant energy user somewhere that I am unaware of. I really appreciate this input.

    Now that I seem to be maintaining temps(although I'm certainly not as efficient as I could be), I might need to shift my focus for a bit.

    This also explains why I was scratching my head saying, "even if my unit runs all the time, it shouldn't be using this much electricity".
     
  4. Stickman

    Stickman Member Forum Leader

    I’m in downstate NY and just got my electric bill for usage during the past month. It’s been somewhat hot and humid here - high 80’s to low 90’s air temp. I’ve got a 4 ton 2 stage GSHP in a fairly leaky 1954 house. I keep the stat set to 72 all day every day. My average daily whole house electric usage was 68 kWh per day.
     
  5. gorilla33

    gorilla33 Member

    I received and installed the Sense Energy Monitor last night. I have already found something that I think may be the smoking gun, but I'm not sure what it is. When my HVAC kicks on, I see an approximate increase in instantaneous usage of approximately 4000Watts. This seems reasonable based on what @SShaw listed above. However, when it is running continuously you can see a trend where it kicks up much higher for a period of several minutes. The load typically spikes to over 9000Watts. These spikes seem to last in 6 minutes, with 10 minutes between spikes. This happened all night long.
     

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  6. gorilla33

    gorilla33 Member

    Found it! It is the Water Heater. I was able to pick out the trend, it runs for about 30 minutes an hour, in 6 or 7 minute increments. It is a 4-4.5kW user. That's over half of my electric bill.
     
  7. SShaw

    SShaw Member

    That's typical power usage for a WH, but it should not come on that often, especially if the geo is supplementing the water heating. With a 90+ EWT your geo unit should supply most of your hot water.

    You indicated your geo has the hot water option. Is it configured correctly? You need to have the hot water option plumbed into an unpowered buffer tank, with the buffer tank supplying the normal WH.

    Are you really using hot water in the middle of the night such that the WH comes on several times per hour?

    Perhaps things are plumbed incorrectly, and the water heater is somehow adding heat to your ground loop, instead of extracting waste heat from the compressor.
     
  8. gorilla33

    gorilla33 Member

    yes i have a separate tank...would a picture help? I dont know if everything is correct or not.
     
  9. SShaw

    SShaw Member

    It should be plumbed something like this.
     

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  10. gorilla33

    gorilla33 Member

    Here is the picture of the unit. It looks similar. I have a circulation pump, and that might be confusing it. I'll be honest, I'm a little confused by some of it.
     

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  11. SShaw

    SShaw Member

    I'm not familiar with recirc pumps, but it look odd to me, and might be causing some issues.
    1) The recirc pump will increase energy usage when installed correctly, so you should expect that.
    2) I believe that normally the pump would be installed at the outlet of the water heater with an added return line tied into the drain of the water heater. This keeps the water circulating through the water heater. Your pump looks to be installed on the inlet to the water heater, tied into the output of the buffer tank. Installed like that it will be pulling cold water out of the bottom of the water heater tank, not hot water from the top of the tank. I don't see where the return pipe is, but it doesn't look like it ties into the bottom of the water heater.
    3) Installed like that, it seems like the pump might pull water from the buffer tank. I don't think you don't want the recirc pump to be circulating water through the buffer tank.

    I'd turn off the recirc pump (and isolate it using the valves if you can) and see what that does to your electric usage.
     
  12. gorilla33

    gorilla33 Member

    I did do that with the recirc pump...results are that it is using about 60W, all the time. So, not great, not the end of the world. How could this plumbing, if wrong, impact my ewt?
     
  13. gorilla33

    gorilla33 Member

    also, the recirc pump is pumping into the heater tank, not out of it. Which also doesn't make sense to me.
     
  14. ChrisJ

    ChrisJ Active Member Forum Leader

    Here is a picture of the way SShaw remarked about recirc pumps location.
     

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  15. ChrisJ

    ChrisJ Active Member Forum Leader

    Double check the DSH in and out plumbing, make sure the out is connected to the drain on the non-powered tank.

    Also the check valve (little rubber flap) inside the cold water nipple has been removed on the top of the non-powered tank.
     
  16. gorilla33

    gorilla33 Member

    I dont want to mess up the lingo, so i'll try to explain.

    The Hot water coming from my Geo unit goes into the top of the non-powered tank. The drain from the non powered tank goes to the "in" of the geo unit.
     
  17. SShaw

    SShaw Member

    Thanks, @ChrisJ. For @gorilla33 setup to work, the line going into the top of the pump would need to be the recirc return line.

    I believe the reason recirc pumps use more energy is not from the 60W pump power, but from circulating hot water throughout the piping, which loses heat to the home, returns colder and needs to be re-heated by the water heater. I'd shut the pump off and see if the WH is still coming on in the middle of the night when no water is being used.

    I'd also note that you are supposed to use copper lines coming off the hot water generator. It looks like you might have PEX. The lines can get hot enough to burst PEX or PVC, so copper is supposed to be used to prevent a flooded basement.

    That would be backwards. You want the heated water going into the bottom of the tank, so it rises and maximizes mixing in the buffer tank.
     
  18. gorilla33

    gorilla33 Member

    I turned the WH back on and the recirc pump off. WH ran for 50 minutes. I’m assuming it’s heating the tank back up.
     
  19. gorilla33

    gorilla33 Member

    @SShaw @ChrisJ can either of you explain how this plumbing issue would make my WH come on do frequently? I’m honestly not seeing what the motive force is to even her the hot water from the geo over time the WH. Also, pretend I don’t even have the geo unit, this WH still shouldn’t come on so frequently, right?
     
  20. SShaw

    SShaw Member

    It might be the recirc that causes the WH to come on often. Leave the pump off and see what happens.

    If connected correctly, the geo heat pump HW generator will make it so the WH rarely comes on. Is you hot water generator pump turned on? I believe there's a switch on the outside of the heat pump.

    In the summer the geo uses waste heat to heat the water, which means it's free. That also keeps that heat out of your ground loop, which increases efficiency of the geo and saves more money. In the winter the geo heats water at the efficiency of the geo heat pump, which is far cheaper than using electric elements. The average efficiency should be over 400% versus 98% for an electric WH alone.
     

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