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  1. #1
    Join Date
    Aug 2004
    Posts
    7
    I replaced a 6 cylindes york compressor and now I am having trouble with oil leaving and not coming back.
    No hot gas by-pass, 3 unloaders 6 txvs with solinoid valves, and no oil seperator.
    I have tried most all I could think of.
    CAN YOU GIVE ME SOME IDEAS AS TO WHAT CAN CAUSE THIS?

  2. #2
    Join Date
    Feb 2003
    Location
    Wichita Ks
    Posts
    1,457
    is the system flooding? how much oil are you going through? possible you have a problem with the compressor. if this is hydraulic unloaders then check oil pressure with it fully unloaded and energize each stage one at a time and watch your oil pressure. it should dip some and then go back to where you started fully unloaded. if you have a unloaded leaking you can loose oil.

  3. #3
    Join Date
    Jun 2004
    Location
    Eugene, Oregon
    Posts
    1,018
    Is the condenser above the evaporator coils?
    "The bitterness of poor quality remains long after the sweetness of low price is forgotten". --Benjamin Franklin
    "Don't argue with an idiot, they will drag you down to their level and beat you with experience". --Mark Twain
    http://www.campbellmechanical.com

  4. #4
    Join Date
    Aug 2004
    Posts
    7

    new copressor oil loss

    I have three unloaders controlled by the suction pressure and staged.
    The condenser is above the evap.
    I have verified that it's not my TXV's.
    The problem occurs when the system runs in a partial or unloaded condition.

  5. #5
    Join Date
    Jun 2004
    Location
    Eugene, Oregon
    Posts
    1,018
    If your condenser is above your evaporator and problem occurs during partial load conditions then I would say your oil is in your evaporators. unless you have double risers with traps the refrigerant velocity would not be sufficient to carry the oil back to the compressor.

    The cause of the original compressor failure may have be due to the lack of oil.

    Just a guess but something to consider.
    "The bitterness of poor quality remains long after the sweetness of low price is forgotten". --Benjamin Franklin
    "Don't argue with an idiot, they will drag you down to their level and beat you with experience". --Mark Twain
    http://www.campbellmechanical.com

  6. #6
    Join Date
    Aug 2004
    Posts
    7
    I have double risers with traps.
    I can get oil back when system loads up but when it runs unloaded ( 2 cylinders are always loaded) the level drops and trip oil safety.
    I have fixed and confirmed all 6 txv's are working properly.
    15 deg. super heat.
    I believe this is why orig. fail also but cant figure out why??

  7. #7
    Check the sizing on the risers if the riser is to large for the flow unloaded it still won't bring back the oil until you have sufficient velocity in the riser also how high is the lift on the riser. Is the system short cycling and is the horizontal run after the riser sloped towards the compressors.

    Just some oil return thoughts

  8. #8
    running unloaded for long periods will force oil out of compr. and lay it in evap coil, flooding, low head pressure, unloaders not set properly, pump down system get oil back in crankcase, set subcooling to 10 degrees, superheat at 20 degree and fully loaded then watch oil presure should have 50 lbs net. then watch as compressor unloads and at what pressure, then watch superheat while unloaded, if it is going to low then raise superheat, it come down while unloaded but just dont let it go like below 8 or 10 degrees. unloading should occur at 58 lbs dx and 55 lbs chillwater. also is compressor rebuilt if so then stop buying rebuilts. make sure you dont have suction driers if you do yankem out.

  9. #9
    Join Date
    Aug 2004
    Posts
    7

    oil loss

    Everyone on this site has been extremly helpful. Ihave used this info and have checked this info earlier but sometimes machines have amind of there own.

    I have babysat this thing and have discovered that all controls are set up right.

    I was on site when this problem happened.

    When the control program shut the system down on low Press.
    switch. The pressure would rise slighty (which is normal) but would cause the low press. sw. to pump down at 30psig.

    I have narrowed to the low press. sw. (for sure is bad) and possible the by-pass timer for the oil press. safety (20 yrs old. original.

    Thanks all!!!

  10. #10
    Join Date
    Aug 2000
    Location
    Austell, Ga.
    Posts
    1,294
    If your oil loss is occuring @ periodsof unload & other factors are normal, you simply have a "Velocity" problem..
    Get that Head Pressure up to sayyyy' 150PSI over Suction at minimum and see if the oil loss problem does not just go away...
    Bet Ya' a dollar to a hole in a do-nut it will......
    Ain't "None" of us as smart as "All" of us..

  11. #11
    Do you have two different size risers? A properly installed double riser should have a minimum of 1000 fpm velocity at the minimum load. The larger riser should be sized for normal gas velocity for both pipes at full load. The following references, Trane Reciprocating refrigeration Manual, Copeland's Refrigeration Manual-part 4 system design, and Vilter's Refrigeration Piping Data manual are great resources for this info.

    If you already have properly sized suctions risers, but your load is actually running quite lower than the last stage of unloading, then I would recommend adding hot-gas bypass between the TXV and the refrigerant distributor (if used). This is not neccessarily easily done, but if the oil is trapping out in the evaporator due to low velocity, then this will surely help. Sporlan does a good job of explaining how to apply hot gas to these systems.

  12. #12
    Join Date
    Oct 2000
    Location
    St. Augustine, FL. USA
    Posts
    46
    Do the basics, What was system designed to do? Has load changed?? Proper airflow??? How old is system???? If it ran for years and now has lost a pump, what EMS guru is asking system to do things outside design?????

    I'm assuming this is piped to multiple AHU/Evap's with 2 stage coils?

    Info-Info-Info!!

  13. #13
    what would age have to do with oil pressure. compressor is new.

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