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  1. #1
    Join Date
    Feb 2004
    Location
    KY
    Posts
    108

    Confused

    Yesterday our install crew put in a Trane HP Model# 2TWA0060A4000AB tied to a Trane A/H # TWE060A4000EL. They said it was cooling well when they left,
    Today I get the call that it's short cycling and the occupant shut it off. Of course Im thinking its leaking but I get there and see equalized pressures of 150 PSI. I start it up and the head pressure never rises, but the suction drops to less than 10 and shuts off on LPS. This drop takes about 20 seconds. Service valves are open, I moved my gauges to the ports near the Rev Valve and get the same readings. There is nothing beween the comp dischage and the rev valve gauge port except for a muffler. I was thinking restriction at the txv but wouldnt that raise the discharge pressure as the suction drops? Again I get no pressure rise on the discharge. Its almost like the compressor is pulling in the gas but not discharging. Is this possible? I had to leave today to go to another appointment, but Im sure Ill be back tomarrow. Compressor pulls 5 amps (rated for 9.4 RLA) during its short run time ....ANY SUGGESTIONS?

  2. #2
    Join Date
    Aug 2002
    Location
    Greenville SC
    Posts
    436
    Sounds like a restriction at the TXV. If it is cool enough outside you might not see the head pressure go up as the unit pumps down. Did your guys install a filter drier in the liquid line?

  3. #3
    put a thermometer on the suction and liquid line and check subcooling and superheat. now if you have normal to high subcooling that means charge is ok or overcharged and if superheat is high then you have a restriction. if subooling is low and superheat is high then you have low charge.

  4. #4
    Join Date
    Jun 2004
    Location
    Clayton,NC
    Posts
    407
    I had one I did in January. Charged it in heating and it worked great. A month and a half later when things got warm I got a no cool call. In cooling it ran a 30/ 200. When I switched the reversing valve and it went to heat mode the pressures were fine. Turned out that the orfice in the AHU was bad. It was never drilled all the way through at the factory. It had a hole on the inlet but was close off at the outlet. $2.50 and 3 hours later it was cooling fine. TXV's are more fun to change but thats probably what it is.

  5. #5
    Join Date
    Nov 2003
    Location
    Boston
    Posts
    600
    See my username for my guess.

  6. #6
    Join Date
    Dec 2002
    Location
    davenport, iowa
    Posts
    778
    you are not gonna get SH and SC in 20 secs. !!!
    Da Threadkilla

  7. #7
    Join Date
    Feb 2004
    Posts
    534
    Just my two cents here but is your reversing valve changing over? you need system pressure to switch over valve are you taking true suction reading? I could be way off base here but just wanted to ask!

  8. #8
    Join Date
    Dec 2002
    Location
    Tampa, Florida
    Posts
    706

    Arrow sounds like...

    sounds like a bad txv at the evap. - would the head pressure rise, no. if the txv was restricting or closed, in essence, it would do & act the same way as if you were pumping down the system. suction drops and head stays the same or lowers a bit.about 5 years ago, had a trane twe065, variable speed do something similar. but the txv didn't close all the way down, just enough to keep unit from going off on lps. take sub-cooling and superheat readings. they will tell you what's going on with the refrigerant flow.

  9. #9
    Join Date
    Feb 2004
    Location
    KY
    Posts
    108
    an update this situation, This system is one of 6 identical set ups in a storage warehouse and this one is the only one having problems... Anyway I went back the next day and with out a txv in my hands, decided to try to blow out the system. I recovered, then cut loose the A/H and blew nitogen in/out, back/forth. I put it all back together with a new filter drier, evac and rechage, and IT WORKS. I didnt actually see any debris come out, so only time will tell if I actually removed the restriction or just relocated it to come back and haunt me later.

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