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Trane Geothermal Heat Pump - compressor intermittently locking out

Discussion in 'Maintenance and Troubleshooting' started by sherry999, Mar 9, 2009.

  1. sherry999

    sherry999 New Member

    I have a Trane model GSUJ heat pump. It was installed during the construction of my home which is about six years old. It has NEVER worked right in the winter. The first few winters I couldn’t figure out why my electric bills were five times higher than they are in the summer. Finally, I realized that I was running primarily on auxiliary heat. I called my installer out several times over the first few winters. All they ever did was purge the lines and tell me that they couldn’t find anything wrong.
    I live in Maryland. The winters are cold, but not frigid. Average winter temps are lows in the mid-20s and highs in the mid-40s. This year, however, has been extremely cold. We hit single digit temps on more than a few days this year. Unfortunately, this has meant that the problems with the geo have been even worse. By late January, we finally realized what was happening. I noticed that the system was running almost constantly. It was blowing cold air and then kicking the aux heat on to warm the house back up; a vicious cycle that never ended! I was finally able to get the installer out one night when this was happening and they determined that the compressor was locking out. When it locked out, the refrigerant pressures dropped in half. The compressor stopped but the fan kept blowing. I’m not sure if this has been the problem all six years or if this is new. I’ve never noticed cold air blowing out the vents before this winter. However, this winter has been much colder than normal.
    I’ve had several people come out to diagnose the problem and they all have different theories on what is wrong. My installer thinks that the refrigerant has a particle in it that is intermittently clogging the TXV valve so they want to come out and filter the refrigerant. Another company came out and they determined that it could be due to a slightly low refrigerant pressure. My suction pressures run about 50 and my discharge pressures run about 225 in heating mode with a EWT of around 40-45 F. The suction pressure is just below the specs (within one or two PSIG) of the chart provided by Trane. I’m not sure if this is enough to be causing this problem??
    I’ve been doing a lot of research and think that part of the problem could be the length of my loop. I have a horizontal, closed loop system that is 1,000 foot long. About half is buried at 6 feet and the other half at three feet. In talking with a few local companies, they have all told me that I should have at least 2,000 feet of loop. My Trane is a 4-ton system (48,000 BTUs). My house is a single story rambler on a basement. The ground level is about 2300 square feet and the basement is about 1700 square feet. The basement is currently unfinished so the floor is still exposed concrete. I heat everything, including the basement.
    I’ve also contacted Trane directly to obtain some guidance. Of the two techs I talked with, one said that since it only happens when it gets really cold outside, it could be that I don’t have enough methanol in the loop and this is causing ice crystals to form in the heat exchanger. The second tech suggested that the heat exchanger may have some calcium buildup that needs to be flushed out. Do either of these make sense? I thought calcium buildup was more of a problem with an open loop system, but my installer did fill my loop up with well water and I know my water is hard.
    We bought some digital thermometers this weekend and tried to monitor the EWT and LWT. Of course, right now, the air temps are back up in the 50s so the system is working. What we’ve noticed is that after about 30 minutes running the geo, the EWT decreases by about 10 degrees; is this normal? It seems like a huge drop in only 30 minutes. Right now, we have a good differential between the EWT and LWT. This doesn’t surprise me though. The system has always worked fine in moderate temperatures. It is only when it gets real cold that we seem to have a problem.
    Sorry for the long story but we are desperate for any guidance!! We’re almost to the point of giving up on the geo and swapping out for an air source heat pump with oil backup. If there is anything that anyone can suggest to help us pinpoint the problem, we would greatly appreciate it!
  2. geo fan

    geo fan Member

    when your system was locking out was there ice on the entering water line?
    testing how much anti-freeze is in the system is a very easy test takes about 30 seconds
    was that length the trench or the pipe ? how many tons is it ?
    filter and the evap coil clean ?
  3. jrh

    jrh Member

    dont give up!

    It sounds like you might be short looped!Can you verify loop length and diameter? you said you purchased 2 digital thermometers,try to log as much info as you can regarding ewt&lwt ,if you are short looped your ewt will show it.
  4. sherry999

    sherry999 New Member

    Hi and thanks for the quick replies! I didn't see any ice on the entering water line when the compressor locked out, but the compressor itself was covered with frost. The filters and the coil are all clean. How do I test for antifreeze level? If it's easy enough, I'll do this right away. It would be great if this was the problem!

    There are two trenches each 250 feet long. There is one pipe that runs the length of the trench at 6 feet deep and then loops back at three feet deep. This pipe is connected in series to the second trench, for a total pipe length of 1,000 feet. I've called my installer to find out if they used 3/4 inch or 1 inch pipe but he hasn't returned my call yet.

    My system is a 4-ton unit. Our weather outlook for next week shows lower temperatures again, so if this happens, I will definitely monitor the entering and leaving water temps as much as possible and provide this information asap!

    Thanks!
  5. geo fan

    geo fan Member

    I should quilify my statement
    it takes 1 min if you have test strips on you ( which every tech should )
    Im sure you could go to an auto parts store and they will have some way to test freeze protection . might not be perfect if its a different type of antifeeze so if they have multiple tests pick them up to

    If you where short looped I would expect to see ice on both water lines at most times but definitly when it locked out
    ( hinting that your ewt is above or close to 32 which is good )

    I know its a long shot but could it possibly be a 4 year old
    open loop /closed loop dip switch
  6. sherry999

    sherry999 New Member

    Based on your question about the dip switch, I made a phone call to Trane today. They said that my model was not shipped with a freeze protection switch. They said so many people complained about that, they now have an add-on that can be placed on the line to add freeze protection. When I described the problem, the guy said that I could change the low pressure switch so that it won't cut off until the pressure reaches 8. The default switch setting cuts it off at 20. So I'm going to have a local geo company come out (not my installer!!!!) and check this switch. I'm assuming if this is an option they offer, that it will not harm the system to change this setting. I will also ask him to check the antifreeze level while he's here. Hopefully he will have the strips. They are coming out tomorrow morning.

    In the meantime, temps are still up in the 50's so my unit is running fine right now. I will plan to monitor the EWT and LWT this weekend when it's supposed to be a little colder outside.

    Thank you very much!
  7. Mark Custis

    Mark Custis Active Member Forum Leader

    Good Job

    not everyone making or selling and installing geo systems is as sharp as the group here.

    I am GLAD we found YOU.
  8. Geotech

    Geotech Member

    Short

    Your loop is short and I'm surprized that you do not have problems even in the summer. You may also have a problem with your flow center pumps, but the problem with a short loop is that the problem will always show up in the winter.
  9. clarkjo

    clarkjo New Member

    Loop information

    I have a 3 ton in Maryland with 2400 ft of 1" loop. The outbound loop is 8 ft and the retrun is 6 ft. The set up is 4 loops in two 300 ft trenches.

    Only problem I ever had was the thermostat set up cut me off when the outdoor air temp was below 50 deg. This was quickly corrected to eliminat the air temp cutoff.

    best...

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