Split System Freezing Coil

Discussion in 'Maintenance and Troubleshooting' started by PAGeo, Jan 21, 2009.

  1. PAGeo

    PAGeo Member

    I have a 2 ton FHP split unit freezing up around the evaporator and reversing valve. It's been checked for freon leak and that was negative. The "Correct amount" of freon was measured in and it still froze up. It's a closed loop with EWT = 45 and LWT = 41. Any ideas?

    Additional Info: system runs fine in cooling mode in summer, why?
    Closed Loop is in 300 foot vertical well
    Split is in basement, 2 years old
    Air handler is in attic above second floor, 10 years old
    A packaged unit satisfies first floor
    Last edited by a moderator: Aug 29, 2010
  2. hardchines

    hardchines Member Forum Leader

    Are we talking reversing valve in basement unit or TXV valve (thermal expansion valve located on evap .coil in attic?
  3. PAGeo

    PAGeo Member

    The reversing valve in the basement unit is the one freezing up, along with the evaporator and if it runs long enough the compressor also freezes.

    The air handler in the attic has a piston valve.
  4. Mark Custis

    Mark Custis Not soon. Industry Professional Forum Leader

    It sounds

    like either the reversing valve is not fully seated or a check valve is leaking. That assumes the tech doing the refrigerant work is correct on the charge. I have used a very strong magnet to free up a check valve ball.

    Most if not all reversing valves use refrigerant to move the valve body. The tiny tubes that do this can get plugged.
  5. PAGeo

    PAGeo Member

    If it is the reversing valve, could that be the reason it works during cooling and doesn't during heating?

    Last winter we had problems, but that included a bad board, a leaky valve core and air in the loop. After they fixed those isssues, it seemed to work well. We didn't have any problems during the summer. Now, we are having problems again this winter.
  6. Mark Custis

    Mark Custis Not soon. Industry Professional Forum Leader


    the reversing valve could be leaking through in heat mode and not in cooling.

    When they mated the new heat pump to the old air handler did they clean up or replace the refrigerant lines? Either way the system deserves a filter dryer, to remove contaminants and water. Triple evacuation is also good practice. If they opened the system to weigh in a charge they should have installed a new filter dryer and re-evacuated.

    Junk in the refrigerant system can cause a R/V not to seat or not to move at all.
  7. PAGeo

    PAGeo Member

    When they installed the new FHP, they vac'd out the lines but did not replace them.

    When they tested the lines for leaks, they used nitrogen and it held pressure. Then they vac'd out the lines again and weighed in the new freon.

    No new filter dryers have ever been installed, that I am aware of.
  8. hardchines

    hardchines Member Forum Leader

    I agree with all of above, but I would make sure a gauge set was put on system before anything else, they tell all (ok most), freezing up compressor and line to it is a indicator of a low charge! The attic coil was ten years old, I am surprised a new coil with a TXV valve was not installed , 2 ton high efficiency "A" coil is under 200. and a good TXV about 60., makes big difference in system performance, as they say "been there done that", JMO!:eek:
  9. PAGeo

    PAGeo Member

    Once new freon was measured in, the pressures were checked and were normal.

    The fan and coil are in separate boxes, so would it be worth it to replace the whole thing with a variable speed fan or just replace the coil and txv?

    On the other hand, I was told that the problem lies in the FHP not the air handler.
  10. hardchines

    hardchines Member Forum Leader

    If pressure was checked recently, you have one of the problems mentioned above. I would have replaced coil and installed TXV, you can buy a cased coil with TXV installed so it is easy to replace your separate boxed coil, I am not saying that is the fix. I would not replace blower unit if all is well with air flow, save your money.
  11. Mark Custis

    Mark Custis Not soon. Industry Professional Forum Leader


    I am in favor of a new coil and TXV, and a filter dryer. I would guess this is and R-22 system. If that is not the fix it will make for a better system.

    I am trying to get a handle on weighing in a charge on a split system. Especially a mis-matched set up.
  12. PAGeo

    PAGeo Member

    Well, after 5 hours and tearing the whole thing apart, the tech decided it is the reversing valve. I brought it up at the beginning, put they get paid by the hour. Now we have to wait for it to be shipped from FHP. Also, we may look into replacing the air handler with Frigidaire, but not until we get this FHP working correctly.

    Any thoughts on Frigidaire air handlers?
  13. Mark Custis

    Mark Custis Not soon. Industry Professional Forum Leader


    Keep us posted.

    I have had a few, r/valves be bad. Mostly from gunk in the system.
  14. Geotech

    Geotech Member

    need info

    The piston at the evap. coil meters the refrigerant for cooling. It should slide to allow the refrigerant to flow past it during heating this may or may not be the cause of your problem. When a reversing valve does not completely shift it will either hiss or the pressures will be almost equalized between the high and low sides. During heating the reversing valve has very hot gas going through it and it should not freeze. Sounds like low refrigerant levels to me. Would help to have more info like actual gauge pressures, air temps in and out of the unit, water pressures in and out of the heat exchanger.Also type of refrigerant.
  15. PAGeo

    PAGeo Member

    The tech took the piston valve apart and examined it. He said it looked fine. As he worked on the FHP, the pressures varied from low to high. 2 of the 3 lines on the reversing valve were freezing. The tech actually added more R-22 while working on it to see what pressures would do. In fact, he left it open while running the system to draw it back out, but the system pulled more in. He said this was due to the faulty reversing valve. The return air had temp of 68F and outgoing air was 88F. He said the water pressures looked good, but I did not get numbers.
  16. Geotech

    Geotech Member


    If the tech believes that the reversing valve is not working properly thn let him change it out it should be under warranty, if not and that replacing it does not correct the problem then the expense should be on him.
  17. PAGeo

    PAGeo Member

    The tech came yesterday and changed the reversing valve. Set at 72, it satisfied and seemed to be operating well. This morning it felt cooler and the unit was constantly running, never shutting off. So, I took the cover off of the FHP and found freezing again. It is freezing around the accumulator, reversing valve, and started freezing on the compressor where the pipe enters.

    Any thoughts from the pros?
  18. engineer

    engineer Well-Known Member Industry Professional Forum Leader

    Constant run OK during cold weather.

    I hadn't thought about it until now but I figure that if waterside temperatures are near or below freezing then refrigerant lines on low side, including accumulator, would be at or below freezing, so they could ice up if not insulated.

    I'm not a seasoned tech, though.
  19. Geotech

    Geotech Member

    don't pay

    Don,t pay if the system is doing the same thing reversing valves are very rarely the problem in the heating operation because they do not shift on most units during heating. I'm not sure what the problem could be but this has my intrest and will get back with you.
  20. PAGeo

    PAGeo Member

    Upon starting up in heating mode, the accumulator gets condensation on it. Is this normal?

    The freezing starts at the accumulator and spreads from there. Why would this be? What is the purpose of the accumulator, what does it do exactly?

    Attached is a picture of what it looked like this morning, 10 hours after start-up.

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