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residential split system shuts down due to overheating

have an older split system and when its humid and very hot, the compressor shuts off, and then after awhile it will start back up; have learned it may be due to a thermal switch that is protecting the compressor

could the overheating be due to dirty condenser coils that havent been cleaned for quite awhile?

would use of foaming coil cleaner be good to use?



  • icesailor
    icesailor Member Posts: 7,265

    Well, lets see.

    If you had a tribe of pets, and they were shedding like crazy, and the house was cold in the winter, and you called someone to look at the problem, what would you do if they told you that the pet hair and dander was stopping the flow of cooling air through the elements because of the animal hair? Because it was covering the tops of the fins on the elements?
  • elfie
    elfie Member Posts: 266
    its a central ac system - no heat

    its about dirty condenser fin impact on overheated compressor shutdown

    also, could the condenser fan motor/speed cause compressor overheating
  • icesailor
    icesailor Member Posts: 7,265
    Its the same:

    Its the same issue.

    If you found the compressor housing filled with leaves and no cooling air could get through to the fins, the compressed liquid would be way too hot and you wouldn't get the designed cooling.

    What's the outlet liquid temperature? Is it within the parameters?

    When you put your gauges on the lines, does the outlet temperature coincide with the type of liquid (R-22, R 410A) the pressure and temperature shown on the gauge?

    I was trying to say that I would start by cleaning the outside coils. The inside one may be dirty because no one ever changes or cleans the inside filter. Which will wreck the system. Like it did on a customer of mine.
  • unclejohn
    unclejohn Member Posts: 1,833
    Yes it

    Could be a dirty condenser coil. It may also be low on refrigerant. Most newer outdoor unit 10 years or so have single row condenser coil and all you need is hose pressure and no chems are needed. Some older units have a split cond. coil and you need to remove the top of the unit and clean between the coils.
  • elfie
    elfie Member Posts: 266
    dirty coils

    the unit is about 20 yrs old and i hear the foaming coil cleaner would be good to use?

    make sense?
  • icesailor
    icesailor Member Posts: 7,265
    edited March 2014
    Cleaning Coils:

    I'm not a expert AC person but I have installed a few of the Mini-Splits.

    As I understand it, or at least on the ones I installed, they do not have liquid pumped to the inside coil, only gas. The expansion valve is in the outside compressor. If that's true. But if the unit hasn't been routinely maintained, and the inside filter isn't cleaned, the inside coil could be blocked up. Is there any form of Delta T temperature inside?

    The outside compressor unit. Is the coil clean? Is there any hot liquid leaving the compressor going to the coil and is there hot anything going back?

    If the inside coil is dirty and not allowing the free flow of air, the refrigerant can overheat and be ruined and not work.

    If you're a homeowner, you really need a qualified AC technician to check out your problem. 20 years is a long time running for one of these Mini-Splits. 1994 is around the beginning of Mini-Splits in the USA. New ones are far better than the early ones. A competent AC technician will put his gauges on the system and know immediately what is wrong.

    Call a Pro.

    That's what I do when it comes to AC. Its a whole other complete profession with its own set of rules.
  • clammy
    clammy Member Posts: 2,983

    Yes use a foam cleaner and clean your outdoor coil also check your condenser contacts for carbon build up and pitting if so replace chk refregerant charge ,and capactors for  proper mfd .other thing to chk beside amp draw off compressor and outdoor cond fan .Then while operating chk temp difference on indoor coil and sub cooling and super heat on your ref charge ,also chk your compressor leads and termimals for loose connections this can also lead to hi amp draw and over heating of motor winding leading to thermal over load .hope this helps peace and good luck clammy
    R.A. Calmbacher L.L.C. HVAC
    NJ Master HVAC Lic.
    Mahwah, NJ
    Specializing in steam and hydronic heating