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  1. #1
    Join Date
    Jul 2005
    Posts
    24

    Confused

    I have a 3 ton split system I have been working on for a few days It will run fine till the hotest part of the day I cleaned the evaporator, good air flow good amps on fan motor the unit will run 10 min shut down for 10 min and start again I watched this for 1 hr It shud down one time when it restarted the low pressure was 110 and a warm suction line and did not drop I shut it down and restarted it and the low pressure when down to 64 to 66 and ran fine after that beside starting and stoping every 10 mins any idea what would cause the low pressure to stay at 110 once a day ?

  2. #2
    Join Date
    Mar 2005
    Location
    burlington county n.j.
    Posts
    9,642
    what make and model??

  3. #3
    Join Date
    Jul 2005
    Posts
    24
    Rheem RAMB-036JAZ

  4. #4
    Join Date
    Mar 2005
    Location
    burlington county n.j.
    Posts
    9,642
    any idea what is shutting down? are you losing low voltage to unit or is it tripping on a safety in unit

  5. #5
    Join Date
    Jul 2005
    Posts
    24
    it looks like its losing voltage like the theromstate is shuting down the unit

  6. #6
    Join Date
    Sep 2002
    Posts
    510
    It sounds like your internal overload is opening up and shutting the unit down.
    The high suction pressure may be caused by the internal by-pass leaking by.
    listen for the swooshing sound if this is happening.

  7. #7
    Join Date
    Jul 2005
    Posts
    24
    the external contacts are opening

  8. #8
    Join Date
    Sep 2002
    Posts
    510
    I see that your profile says that you are a Maintenance Director.
    So, I don't know how much training you have with Hvac,but if you could get a book on Hvac,it may help you learn what the common components of an air conditioner compressor are.
    with that said,the internal overload opens when the compressor gets too hot, to protect the compressor from any serious damage.It cannot be replaced and is usually located at the compressor terminal location.
    The internal by-pass is inside the compressor and allows hot gas from the high side to bleed over into the low side and is used as a safety device.
    This usually occurs due to extremely high head pressures.

    post some pressure readings along with superheat and subcooling.

  9. #9
    Join Date
    Aug 2004
    Location
    North Richland Hills, Texas
    Posts
    14,914
    Does it have a self reseting high pressure switch, or is it a scroll compressor with the thermister in a well on the top of the compressor, and a liquid line filter drier inside the unit?

    If so, the drier could be partially clogged and the system badly overcharged. Pressures would look normal since the liquid line service port is after the drier, but the actual pressure in the condensor coils would be much higher, possibly tripping a pressure switch (or thermister due to heat in a scroll compressor) and/or causing the internal pressure relief in the compressor to open.
    If more government is the answer, then it's a really stupid question.

  10. #10
    Join Date
    Jul 2005
    Posts
    24
    64 low 215 high 8 sub cooling If the internal overload opens will that open the contacts and shut the whole unit down or just the comp

  11. #11
    Join Date
    Jul 2005
    Posts
    24
    It has a self reseting high pressure switch and two liquid line dryers on it

  12. #12
    Join Date
    Aug 2004
    Location
    North Richland Hills, Texas
    Posts
    14,914
    Originally posted by cjj
    64 low 215 high 8 sub cooling If the internal overload opens will that open the contacts and shut the whole unit down or just the comp
    If it a scroll compressor with the thermister on top of it, the overheating of the compressor when the internal overload opens would cause the thermister to break the control circuit.

    Otherwise, no, the contactor would stay energized.

    Basicly, if the contactor is opening, some control is breaking the control circuit or there is a loose connection somewhere.
    If more government is the answer, then it's a really stupid question.

  13. #13
    Join Date
    Mar 2005
    Location
    Suppy NC
    Posts
    4,509
    do you have one of those power saver switches from the power co. or the power saver t stat from the power co.
    the way you are cycling seems a lot late the way they cycle and only during the heat of the day. if so have it remoned before it ruins your unit

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