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  1. #1

    Disastrous and demoralizing day on a low temp R22 rack...

    Always on a Friday of course. this is an R22 low temp rack. Oil issue upon oil issue upon oil issue, after we fixed the last oil issue. Clogged TEV screens every 6 months. Stuck oil floats and so on and so on. I guess it generates a lot of business for the company...but what does one do to fix this on a long term scale? Convert the whole system to something else, right? Is there something we can convert it to relatively easy or no? New compressors, new TEV's in everything? What else?

  2. #2
    Join Date
    Apr 2013
    Location
    In my head
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    296
    Quote Originally Posted by cswenson701 View Post
    Always on a Friday of course. this is an R22 low temp rack. Oil issue upon oil issue upon oil issue, after we fixed the last oil issue. Clogged TEV screens every 6 months. Stuck oil floats and so on and so on. I guess it generates a lot of business for the company...but what does one do to fix this on a long term scale? Convert the whole system to something else, right? Is there something we can convert it to relatively easy or no? New compressors, new TEV's in everything? What else?
    Isn't the cause of this type of thing the high compression ratio inherent to R-22 low temp systems? I'm still learning this trade, but I'm betting the higher ups at that store likely have remodel plans, and that in the future you'll be replacing it with something more LT friendly...but in the meantime "just keep it running" is probably what they're saying/thinking.

  3. #3
    Join Date
    Apr 2010
    Location
    Winnipeg,Manitoba,Canada
    Posts
    128
    Have changed a few racks over to 507. Oil issues with R-22 on low temp racks I must say have seen a few like you explain.
    Converting is something that you could look into.
    Also is the installation fairly new? Or any changes to the system recently? When the new piping was done, did they purge with nitrogen ?

  4. #4
    Join Date
    Mar 2003
    Location
    Cochrane, AB
    Posts
    604
    Quote Originally Posted by cswenson701 View Post
    Always on a Friday of course. this is an R22 low temp rack. Oil issue upon oil issue upon oil issue, after we fixed the last oil issue. Clogged TEV screens every 6 months. Stuck oil floats and so on and so on. I guess it generates a lot of business for the company...but what does one do to fix this on a long term scale? Convert the whole system to something else, right? Is there something we can convert it to relatively easy or no? New compressors, new TEV's in everything? What else?
    Keep the R2 and convert to AB oil. Sounds like the rack still has mineral oil in it.

  5. #5
    Join Date
    Dec 2000
    Location
    Flat Rock, NC
    Posts
    463
    agree with ab or poe conversion and triple check demand cooling on every compressor.

  6. #6
    Join Date
    Mar 2013
    Posts
    44
    Ripp the whole thing out and put in a secondary loop CO2 system in like all the cool super markets do. XD


    No but I'm having the same problem out at a red apple right now with oil level failures on a split head med/low temp 22 rack. Can't get the damn compressors to equal out. I'll have 2 compressor always good and the center two always getting stuck floats or bad valves that end up in flooding and starving the far two, or the first two just run too damn much and one of their pumps go out. The oil separator has been changed A few times and the system has had countless r11 flushes and a poe convert..

    Mind you, this rack is like older than I am. And has a grossly poor design. Oil problems can be a real on going nightmare on old equipment..

  7. #7
    Join Date
    Feb 2008
    Location
    California
    Posts
    2,066
    I would start with this...
    What's your suction pressure?
    What's your discharge pressure?
    What's your rack suction superheat?
    What's each compressors discharge line temperature?
    If it's gas defrost, what's the differential?

    Something must be wrong. And it isn't just because its LT 22.

  8. #8
    Join Date
    Jan 2004
    Posts
    69
    slam wore out compressors with a fair amount of blowby will cause oil problems that seem to be unsoveable

  9. #9
    Join Date
    Sep 2008
    Location
    Western PA
    Posts
    25,567
    Quote Originally Posted by Phase Loss View Post
    I would start with this...
    What's your suction pressure?
    What's your discharge pressure?
    What's your rack suction superheat?
    What's each compressors discharge line temperature?
    If it's gas defrost, what's the differential?

    Something must be wrong. And it isn't just because its LT 22.



    R-22 low temp requires a little TLC, but it isn't as bad as you are describing unless it is horribly maintained.

  10. #10
    Join Date
    Jun 2001
    Location
    Michigan
    Posts
    12,077
    the good news is, you can solve root cause of whats cooking the oil.

  11. #11
    Join Date
    May 2003
    Location
    Utah
    Posts
    721
    It's not the high compression ratio...it's the thermodynamic properties of R-22 the result in high discharge temperatures in LT applications.

    As a few have said, if the system is set up properly you can operate trouble free. The decomposed oil is a sign of high discharge temperatures. Your job is to find out why.

  12. #12
    Join Date
    Sep 2002
    Posts
    12,280
    Why don't you try running a synthetic oil? What are the clogs? Sooty looking yak? Have you ever had a head off? Are the valve plates all black with sooty looking yak?

    Low temp R-22 runs huge DSH and DT numbers. Mineral oil doesn't like it and will coke. Liquid injection will work to some extent but going to a synthetic oil which will take the high temps in the heads would be a better idea I think. POE will run you silly with cleanup and filter changes for a while so maybe that Calgon oil (it pisses me off that I can't remember the name right now) would be for the best. I used to use it all the time on compound compression low temp compressors.

    PHM
    -------






    Quote Originally Posted by cswenson701 View Post
    Always on a Friday of course. this is an R22 low temp rack. Oil issue upon oil issue upon oil issue, after we fixed the last oil issue. Clogged TEV screens every 6 months. Stuck oil floats and so on and so on. I guess it generates a lot of business for the company...but what does one do to fix this on a long term scale? Convert the whole system to something else, right? Is there something we can convert it to relatively easy or no? New compressors, new TEV's in everything? What else?
    PHM
    --------
    The conventional view serves to protect us from the painful job of thinking.

  13. #13
    Join Date
    Jun 2001
    Location
    Michigan
    Posts
    12,077
    Quote Originally Posted by bunny View Post
    It's not the high compression ratio...it's the thermodynamic properties of R-22 the result in high discharge temperatures in LT applications.

    As a few have said, if the system is set up properly you can operate trouble free. The decomposed oil is a sign of high discharge temperatures. Your job is to find out why.
    high compression ratios are so related to high discharge temperatures no matter what gas or temp. Page 3.

    http://www.hvacrinfo.com/cope_ae_bulletins/TAE1268.PDF

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