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hvac tech

I have one thats giving me some problems. Have an existing r-22 system with a txv external install. Outside unit is heil derivitive inside is a carrier air handler. Outside unit was installed last year by someone else, i replaced air handler two years ago. Last month tested system, was working fine for about 15 min, presures normal superheat amd subcool good, then head would slowly climb and continue to climb untill cut out on interal limit. Talked to local tech support he said posible restriction in filter dryer or the txv was shuting prematurely. Txv was still under warrantee so replaced both filter dryer and txv charged back and tested seam to work well. Customer called back today and went to test, found compressor out on limit, cooled to reset, and tested and systemnisnworking well, outside temps were only 68 and inside was 67 so no load on unit today, most likely will go back to test again once it gets hot. Anything you could suggest to help me track down problem would be great.


  • Mac_R
    Mac_R Member Posts: 117

    I am assuming that you use nitrogen when brazing in the new line dryer and TXV.  If you did not then the oxidation could break off and clog the TXV.  What were your sub cool and super heat readings?  What were your pressures?  What were your line temps?  What was the temp drop across the coil?  What were your supply and return temps?  Need lots of info.  No load could slug the compressor and make it not work so good.  
  • Techman
    Techman Member Posts: 2,144

    This system worked good last summer? What is going off on the comp ,the internal overload ( electrical) or the  internal hi press relief?With a restricted TXV ,I think both pressurers would go down. What were the press's?. Cond fan motor slowing down after awhile?
  • FitterFreds
    FitterFreds Member Posts: 15
    restricted LL

    Chunk of solder rolling around in the LL. Install a High & Low Pressure safety w/ a tattletale. TXV bulb lost charge? Remove sensing bulb and hold it in your hand to see if that changes the pressures at all
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