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Thread: Oil Pressure

  1. #1
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    Oil Pressure

    Technical Systems M# 20A0CS40 460 VOLT Condenser, Dunum Bush Air Handler very old. Copeland compressor model 6DS3R40M0-TSN-800. epr, suction acculator, reciever and hot gas defrost.

    I am running 40 # suction 225# head pressure. 11 sc and 15 sh. 2 unloaders. Room temp to maintain 35 degrees. I have 2 systems and both are doing same thing.

    My problem is loss of oil pressure. Solenoid holds on pump down, compressor valves do not leak by. 1 Unloader unloaded all the time the other unloader loads and unloads. oil foaming slightly when fully unloaded and a lot of foaming when partial unloaded. crankcase hot.

    Any suggestions. Are these comprssors use hot gas bypass can you change to suction cutoff. i am stumped. Oil pressure never gets over 15# net oil pressure then will go to 10 and 5 at various times.

    Any suggestions would be appreciated.

  2. #2
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    Sep 2006
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    Sump screen clean?

  3. #3
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  4. #4
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    How does the oil taste?

  5. #5
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    I think it has to do with the crankcase being to hot and thinning out the oil? I need to know if these compressors use suction cut off unloading or just bypass. I got 2 systems doing the same thing and one compressor is fairly new. But it could be the screen and thats one thing i will check.

  6. #6
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    Quote Originally Posted by HJ Controls View Post
    I think it has to do with the crankcase being to hot and thinning out the oil? I need to know if these compressors use suction cut off unloading or just bypass. I got 2 systems doing the same thing and one compressor is fairly new. But it could be the screen and thats one thing i will check.

    While thinning oil is a possibility, I seriously doubt it.

    Start with the screen. Move to the pump.

  7. #7
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    Quote Originally Posted by Phase Loss View Post
    How does the oil taste?
    With its taste buds, I would suspect.
    "The problem is the average person isnt tuned in to lifelong learning, or going to seminars and so forth. If the information is not on television, and its not in the movies they watch, and its not in the few books that they buy, they dont get it" - Jack Canfield

  8. #8
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    Aug 2010
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    Dearborn MI
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    Copeland hasn't used bypass style unloading for many years. The compressor you are asking about is the new Copeland model number meaning that it can't be very old. What happened to the last failure? The screen probably is plugged, but the contaminants are from the failed connecting rods. The low oil pressure is the result of worn rods caused by oil that is extremely diluted with liquid refrigerant. You need to address the floodback problem and prevent another compressor failure.

  9. #9
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    Jul 2012
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    Western KY
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    Had a TS chiller, believe it has same comp, doing same thing. Comp had been replaced, by different company, previously. Ended up finding oil log was the problem. Pulled 6 gal of oil out of it and cleared rite up.

  10. #10
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    Aug 2010
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    Dearborn MI
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    I don't understand. How could a high oil level cause a low oil pressure problem? Did something else change in addition to you removing the extra oil?

  11. #11
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    I know rite? What we had was oil logged cooler/evap which caused flooding which foamed the sump.

  12. #12
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    Quote Originally Posted by remanworld View Post
    The low oil pressure is the result of worn rods caused by oil that is extremely diluted with liquid refrigerant. You need to address the floodback problem and prevent another compressor failure.
    How could he be having floodback when his SH is 15*F and the crankcase is hot? Do you mean flooded starts?

  13. #13
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    Quote Originally Posted by Push It View Post
    How could he be having floodback when his SH is 15*F and the crankcase is hot? Do you mean flooded starts?
    Didn't say he was. Said I had similar issue and that's what we found.

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