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  1. #1
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    -80 freezers question

    Hi all,

    Can someone explain to me about the problem with oil circulation for the -80 freezers? I believe its called oil logging. I get several calls a year about a -80 freezer not maintaining temperature and will hover around -65 to -70. Shutting it down for a good 24 hrs seems to usually fix it. Just wondering why this is a problem that cannot be corrected by any other means.

    Thanks

  2. #2
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    Usually those systems have oil separators to keep the oil out of the evap coil to help with this issue but no oil separator is 100% effective.

    Oil will still travel with the refrigerant and go in the evap coil.
    Since the evap temps are so incredibly low on these systems, the oil can become very thick/wax like and basically cause poor heat transfer.
    Unplugging it for 24 hours allows the oil to flow better and upon restart it gets pulled back into the compressor.

    Sent from my SM-G975U using Tapatalk

  3. #3
    Join Date
    Mar 2015
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    Medford, N.Y.
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    Cascade?

  4. #4
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    Aug 2002
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    Southold, NY
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    A few Oz Pentine

  5. #5
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    Dec 2018
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    Thread Starter
    Quote Originally Posted by TechmanTerry View Post
    Cascade?
    Hi Terry, Yes. All -80 freezers are typically cascade.

  6. #6
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    Thread Starter
    Quote Originally Posted by UmmScott View Post
    Usually those systems have oil separators to keep the oil out of the evap coil to help with this issue but no oil separator is 100% effective.

    Oil will still travel with the refrigerant and go in the evap coil.
    Since the evap temps are so incredibly low on these systems, the oil can become very thick/wax like and basically cause poor heat transfer.
    Unplugging it for 24 hours allows the oil to flow better and upon restart it gets pulled back into the compressor.

    Sent from my SM-G975U using Tapatalk
    Ok Thanks. That was what my understanding as well. Just seems like a real problem if the lab doesnt have a spare freezer to transfer everything over temporarily. Would shutting it down and loading it up with dry ice to keep the temp down still allow the oil to thin out again?

    Thanks so much

  7. #7
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    Jan 2008
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    You may see Pentane or Ethane as part of the refrigerant charge . think of the P or E , as an oil additive and not a refrigerant . Still manufacturers want a warm up every so often , to fully bring oil back from the evap.

  8. #8
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    Mar 2015
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    Quote Originally Posted by navyguy1 View Post
    Hi Terry, Yes. All -80 freezers are typically cascade.
    2 stage or 3 stage?

  9. #9
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    Dec 2018
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    Thread Starter
    Quote Originally Posted by TechmanTerry View Post
    2 stage or 3 stage?
    Typical 2 stage. High side, low side. Some older and many newer units. Seems like the newer ones are having the most trouble with oil logging.

    Thanks

  10. #10
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    Dec 2018
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    Thread Starter
    Quote Originally Posted by COOLJIM View Post
    You may see Pentane or Ethane as part of the refrigerant charge . think of the P or E , as an oil additive and not a refrigerant . Still manufacturers want a warm up every so often , to fully bring oil back from the evap.
    Thanks for your input. Does the newer refrigerant blends have anything to do with it? Seems to be more problematic with the newer units less than 5 years old.

  11. #11
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    Jan 2008
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    LEHIGH VALLEY, PA
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    Always the oil . Back when r503, r13 r14 r13b1, were in use , POE was not used .

  12. #12
    Join Date
    Feb 2010
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    If the same specific unit is going down because of oil logging more often than once a year, I would call that a problem. But usually they run for several years after letting them warm up.

    If a facility can afford to buy these things they can afford an extra to put the product in. But inevitably they start using the spare also.

    Per most manufacturer instructions they need to be warmed up once per year for this reason.

  13. #13
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    Jan 2010
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    If they don't have a spare freezer then their product is obviously not that important.....
    Quote Originally Posted by navyguy1 View Post
    Ok Thanks. That was what my understanding as well. Just seems like a real problem if the lab doesnt have a spare freezer to transfer everything over temporarily. Would shutting it down and loading it up with dry ice to keep the temp down still allow the oil to thin out again?

    Thanks so much
    Sent from my SM-G965W using Tapatalk

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