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!