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  1. #1
    Join Date
    Jun 2009
    Location
    missouri
    Posts
    19

    Carrier lock out problem

    I am hving issues with a Carrier M.N. 38ah124a621da.
    When it comes out of unoccupied, or free cooling, Unit will restart, then lock out. I have traced the problem to the oil pressure relay. I have checked my refrigerant levels, and all is well. I have discovered the oil pressure relay is locking the unit out. If I reset unit, and jumper across the relay for a minute, I then get control voltage, and am able to remove jumper. Unit then runs the rest of the day, cyclilng as it should until it goes into unoccupied, or free cooling. This is happening on both circuits. I have checked my oil pressure, and found it to be approx. 20 lbs. This is adequate according to my data sheet. I am wondering if I have an oil switch problem, or if the problem is in the timer motor. Any advice or help would be appreciated.

  2. #2
    Join Date
    Apr 2006
    Location
    mechanical room
    Posts
    1,266
    are crankcase heaters working ?

  3. #3
    Join Date
    Jun 2009
    Location
    missouri
    Posts
    19

    Carrier lock out problem

    The crankcase heaters are working. Thanks for responding. This has been an ongoing problem. Any suggestions are appreciated.

  4. #4
    Join Date
    Jul 2007
    Location
    Mount Airy, MD
    Posts
    7,281
    The OD temps in the morning are when firing up for the day is?

    It is more then likely a flood back on start up causing the lockout, you need to insure that anything that could cause this is addressed.... and

    Should all those basis be covered, then consider adding a delay on make timer to the OP switch and give it another few minutes to get the ball rolling again.

    Those Carlye compressors will be just fine with low oil pressure for a few minutes, them things are tough.

  5. #5
    Join Date
    Jun 2009
    Location
    missouri
    Posts
    19
    The OD temp. varies. This has happened when free cooling is disabled at 60 degrees. It has also occurred when the unit is shut down for load shedding. 100 degrees. It doesn't normally happen on free cooling. It seems frequent when the unit goes into unoccupied, or is shut down for any reason. This past winter, when weather began warming, unit was fluctuating between free cooling and normal operation, it transitioned as it should have. In order to avoild the problem, I leave the unit in occupied mode. It operates as it should when in this mode.

  6. #6
    Join Date
    Jul 2007
    Location
    Mount Airy, MD
    Posts
    7,281
    It would seem that you liquid refrigerant is piling up in evaporator and causing the flood back on start up. Assuming that this has been a long time issue....

    and

    "If" what you say is true, one minute bypassed and as is swell, then I would consider up'ing the timing as previously suggested for your OP.

    It's either that or your looking at major surgery to correct/prevent the momentary flood back.

  7. #7
    Join Date
    Jun 2009
    Location
    missouri
    Posts
    19
    Thanks to all for the information! This has been a big help. I will exhaust all of these possibilities, and see if this makes the difference. Thanks again. Zorrithod

  8. #8
    Join Date
    Apr 2006
    Location
    mechanical room
    Posts
    1,266
    can you varify that the outside air dampers are closed when the compressors come on line

  9. #9
    Join Date
    Aug 2009
    Location
    Michigan
    Posts
    88
    I just had the Carrier class on the new veriable speed compressor today. The instructor mentioned somthing about this today. He said when it comes out of unoccupied, it will lock itself out (I think he said for 2 hours) to ensure the crank case oil is heated.

    I hope this helps.

    Maybe someone who was paying attention in the class will come along and clean this up for me.

  10. #10
    Join Date
    Jun 2009
    Location
    missouri
    Posts
    19
    I have verified that the dampers are closed when unit comes online.
    When it locks out... It stays locked out until unit is reset by toggling the condenser fan circuit, or interrupting power.
    I appreciate all the info.

  11. #11
    Join Date
    Jul 2007
    Location
    New Jersey
    Posts
    3,031
    i wonder if you may be loosing oil pressure at night time when it colder out and the refrigerant velocity is at it's lowest

    make sure the ambient temp fan cycle control is working if equipped with one
    “If I have seen further than others, it is by standing upon the shoulders of giants.” ~ Sir Isaac Newton


    I'm learning all the time, the tombstone will be my diploma!!!


    Did you ever stop to think, and forget to start again?

  12. #12
    Join Date
    Jun 2009
    Location
    missouri
    Posts
    19
    Tommy1010
    My fan cycling switches are operating normally. The unit doesn't shut down when it's running. Only when it shuts itself down for free cooling, or if it goes into unoccupied, or we load shed. OD temp. doesn't seem to enter into the equation.
    I thank you for your interest in helping me solve this problem.

    Zorrithod

  13. #13
    Join Date
    Jan 2007
    Posts
    60
    Is the outdoor unit above the indoor and if it is are there traps installed in the line set?

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