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  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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    Sump screen clean?

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  4. #4
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    Sorry working a lot of ot. System was not flooding. the discharge pressure relief was week. The oil screen was plugged up. I didnt believe it as this compressor was changed out a few weeks ago. Not by me. I got to thinking which is dangerous but this system had a hot gas defrost 4 times a day. The hot gas opens liquid line solenoid closes therefore in defrost bypasses liquid driers. So I pulled the screen and YOU WERE RIGHT. Changed the oil and driers. Thanks for the help.

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    Quote Originally Posted by HJ Controls View Post
    Sorry working a lot of ot. System was not flooding. the discharge pressure relief was week. The oil screen was plugged up. I didnt believe it as this compressor was changed out a few weeks ago. Not by me. I got to thinking which is dangerous but this system had a hot gas defrost 4 times a day. The hot gas opens liquid line solenoid closes therefore in defrost bypasses liquid driers. So I pulled the screen and YOU WERE RIGHT. Changed the oil and driers. Thanks for the help.

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    How does the oil taste?

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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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    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.

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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?

  10. #10
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    Thats a good point that I overlokked. The foam in the sight glass is a strong indicator of liquid mixing with the oil however. Also, it sounds as if the compressor is oversized for the system. If one unloader is NEVER loaded and the other cycles often, is it not possible that the TXV is hunting which would allow liquid to pass through into the compressor in varying amounts? That would account for the different amounts of foam (liquid) that is seen in the sight glass?

  11. #11
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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.

  12. #12
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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.

  13. #13
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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.

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