What causes a low pressure lockout?

Discussion in 'General Discussions' started by njcturnquist, Nov 10, 2008.

  1. njcturnquist

    njcturnquist New Member

    Considering Open Loop

    We are in Upstate New York, just west of Albany. Our home is a 1900 sq. ft. 175 year old brick farmhouse with a 1200 sq. ft. newly renovated addition. Currently we have oil-hot-air. We use 1500 gallons of oil per year to keep our house at 60-62 degrees in the winter (48 degrees upstairs)! We hated the high cost of not being comfortable and also wanted to explore green technology. So, here we are.

    We had a home energy audit done in August. Based on that, we installed duofold window shades on all our windows, which should have some impact. Based on the energy audit, he recommended an 87,000 BTU/hr groundwater source heat pump with an efficiency of 3.3 COP.

    This information was given to a geothermal heat pump contractor. His estimate/quote is for the following:
    Invision 6 ton (R410A); 2H/1C/1DHW (COP 3.1 @ 32 degrees EWT, (2nd stage), 3.2 @ 41 degrees (1st stage); a/c EER 15.3 @ 70 degrees F). A 10 KW slide-in Electric heater for backup heat. 80 gal. electric HW tank (2" foam). Also modifications to existing ductwork as well as sealing and insulating ductwork. All in all, his estimate (which is on the "high side") is just about $30,000.

    My test of our well (which we use for our water) showed 11 gpm. We do have hard water and use a water softener.

    We understand that the water exiting the system has to go somewhere - there is a small pond on the other side of our driveway, down a hill, which is owned by someone else and is their backup "farm pond" - they have never used it for such. We would probably send the water that way. It would come out of the pipe at a point lower than where our water pipes into the house.

    In general, does all this seem okay?

    How do I know if the system has been oversized?

    Is the hard water a problem - does the water go through the water softener?? Is there something we should do to condition the water before it goes through the system?

    What type of electric expense per month should we expect?

    We live way out in the country, but own only 2/3 of an acre. There is not much room for a closed loop. The only thing (I think) that bothers us about the open loop is the "wasted water" as well as the uncertainty that our well is adequate to the task. Are there other things we should be concerned about?

    Will we be WARM??? 65 degrees would be nice!

    Any feedback would be welcome.

  2. Palace GeoThermal

    Palace GeoThermal Well-Known Member Industry Professional Forum Leader

    Hi Jackie,

    First off, the system will not be oversized. A 6 ton heat pump will give you about 65,000 BTUh, the 10 KW backup will give you another 34,000 when needed.

    Hard water will be a problem. You run the risk of scaling damage to the heat exchanger inside of the heat pump. Running the water through a water softener is not practical.

    You should explore a horizontal loop system. My lot is 1/4 acre and I have horizontal.

    My best guess on cost is a yearly heating bill of $400 - $600.

    You should be able to keep the house at least 70°
  3. njcturnquist

    njcturnquist New Member

    That is very helpful. We are really into the idea of geothermal for both economic and environmental reasons, but are VERY nervous about the size of the investment and the uncertainties.

    Another question is the fact that we would be using our only well. What do I do to ensure that our well won't run dry? Is there a test? Or do people just hope for the best? My husband is now thinking closed loop is really what we should do. Any thoughts?
  4. Palace GeoThermal

    Palace GeoThermal Well-Known Member Industry Professional Forum Leader

    The uncertainties of open loop can loom large. Your unit will need at least 12 GPM when running. If you think of run times of 12 hours / day then you will be pumping close to 9000 gallons per day. If you do that for 4 months then you are over 1 million gallons. If there is any question about your well and the energy required to pump that much water, then you should consider a closed loop.
  5. TCooper4653

    TCooper4653 New Member


    I agree with palacegeo. Unless you have a large number of trees, you can make a horizontal loop viable on your property. This would be very much preferred to an open loop and would have much lower long-term maintenance.
  6. cgreen

    cgreen New Member

    Water taken from a well should be place back into the ground and not allowed to run-off into a stream, etc. Taking 9,000 gallons / day from the ground and allowing it to run-off can be very bad, environmentally speaking, and could effect others who rely on ground water in the area.

    Open Loops can be efficient when run off of shallow wells (say < 100 feet deep or so). If the well gets too deep then it takes too much energy to pump the water out of the well and a closed loop starts to make more sense.

    I also find open loop systems noisy because of the flow control valves, etc. The noise issue can be a significant issue.
  7. alesia

    alesia New Member

    We have a new system that experienced a low pressure lockout a day or two after installation. After this happened, the installer purged the system (with a purge cart) and added anti-freeze. 24 hours later, it once again went into a low pressure lockout. What are the causes of a low pressure lockout and what diagnostic procedures do you recommend?
  8. Mark Custis

    Mark Custis Not soon. Industry Professional Forum Leader

    clip the jumper

    The board need to know you changed fluids.
  9. geoloop

    geoloop Member

    What is the model # of the unit you had installed?
  10. alesia

    alesia New Member

    Model # HP150 1XL.

    Also a couple of other things to note:
    They are using the coolant R-410
    We had the unit retro fitted into a 1960s rambler
    It has been unusually cold (althouth it is supposed to warm up later this week).
  11. teetech

    teetech Member Forum Leader

    Stick shift or automatic? :lol:
  12. sunnyflies

    sunnyflies Member Forum Leader

    Very funny! Good one. :lol:
  13. Bergy

    Bergy Member Industry Professional Forum Leader

    Retrofitted? Is this a "NEW" unit or an old unit moved to another house? What kind of loop field was installed?

  14. alesia

    alesia New Member

    New unit, new field, old house. Its a horizontal field with the "slinky" configuration.
  15. silkowskij

    silkowskij New Member

    We have the same problem yet our system has been in and running for 7 years and this is the first time we have had a problem. Its a new house, new system (7 years ago) with a ground loop slinky configuration. We are running an Econar Geosource 2000 heat pump. The system first locked out on low pressure 3 weeks ago and we have been struggling ever since. Its the home of my mother in law who is 75 and living alone so any help would be great. We have purged the system of air several times. We have changed the Grundfos Geo-flow pumps yesterday. We are maintained a 5 degree loop field differential in and out (23.9 degrees F to 28.9) with an 8-10 degree pressure differential. This week it ran for a week before locking out (locked out yesterday and we changed the pump). We also had "shocked" the transfer plates within the pump to remove scale (minimal results- very clean). We also checked the antifreeze level in the fluid in the ground loop and that was good to zero degrees.
  16. teetech

    teetech Member Forum Leader

    I hope your not using glycol with freeze protection down to zero because it will get thick as molasses.

    Do an accurate HE on the unit as this will tell if the units refrigeration system is working properly.
  17. K cole

    K cole New Member

    One thing no one seems to mention in 'lockouts' is -a DIRTY AIR FILTER / LOW AIR FLOW will cause lockouts, both HIGH and LOW-.
    Deuce likes this.

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