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  1. #14
    Join Date
    Feb 2010
    Location
    In a boiler room
    Posts
    7,067
    Bernoulli's Principle only applies if the velocity inside the pipe that has a small hole is so high that it starts drawing air into the hole and not letting any refrigerant out.

    Lets just take a low temp running R404a with a -15 evap temp, 20 psig, and a small hole in the suction pipe. The velocity would have to be extremely high to ever reverse the 20 psi gas leaving the pipe and start drawing in air.

    For a leak to leak gas out and suck gas in at the same time is completely impossible. You either have to take the pressure inside the pipe down to negative, or get the velocity so high it would create a slight vacuum at the leak(not gonna happen in a refrigeration system, velocity would never get that high). Maybe if you got the pressure down to .5psig you might have enough velocity to suck a little air in, maybe.

    Urban Legend.

    The more likely cause of getting moisture into a system would be having a leak in the low side and some intermittent restriction causing negative pressures at times, or a pump down system that is pulling down into a vacuum due to pressure switch set wrong.

  2. #15
    Join Date
    Sep 2008
    Location
    Western PA
    Posts
    25,546
    Quote Originally Posted by chuckcrj
    Bernoulli's Principle only applies if the velocity inside the pipe that has a small hole is so high that it starts drawing air into the hole and not letting any refrigerant out.

    Lets just take a low temp running R404a with a -15 evap temp, 20 psig, and a small hole in the suction pipe. The velocity would have to be extremely high to ever reverse the 20 psi gas leaving the pipe and start drawing in air.

    For a leak to leak gas out and suck gas in at the same time is completely impossible. You either have to take the pressure inside the pipe down to negative, or get the velocity so high it would create a slight vacuum at the leak(not gonna happen in a refrigeration system, velocity would never get that high). Maybe if you got the pressure down to .5psig you might have enough velocity to suck a little air in, maybe.

    Urban Legend.

    The more likely cause of getting moisture into a system would be having a leak in the low side and some intermittent restriction causing negative pressures at times, or a pump down system that is pulling down into a vacuum due to pressure switch set wrong.
    We need the Mythbusters!!


  3. #16
    Join Date
    Nov 2010
    Location
    MN
    Posts
    144
    Check out this video on YouTube of a guy pulling a vacuum on a clear bottle of POE that came out of a new scroll compressor. http://www.youtube.com/watch?v=NzXO8...e_gdata_player

  4. #17
    Join Date
    Sep 2008
    Location
    Western PA
    Posts
    25,546
    Quote Originally Posted by PMARS2345
    Check out this video on YouTube of a guy pulling a vacuum on a clear bottle of POE that came out of a new scroll compressor. http://www.youtube.com/watch?v=NzXO8...e_gdata_player
    Means nothing.

    Yes, some moisture came out of the oil.


    After he's done, send that stuff out for an analysis and see what the moisture content is.

    You'll be in for a surprise.

  5. #18
    Join Date
    Nov 2010
    Location
    MN
    Posts
    144
    Quite a few statements on Poe oil here, any references to back then up? I'm nottt doubting what is said would like more info for learning?

  6. #19
    Join Date
    Sep 2008
    Location
    Western PA
    Posts
    25,546

  7. #20
    Join Date
    Nov 2010
    Location
    MN
    Posts
    144
    Thanks

  8. #21
    Join Date
    Feb 2012
    Location
    PA
    Posts
    27
    POE is definitely a cock sucker.. Had a bad burnout years ago and tried for days to clean it up. The only thing that seemed to work was heating and agitating the areas of the system with oil laying in them(crank case, seperator, suc line trap, and accumulator). After 2 days of runing, the oil tested ok in the field, but im sure a lab analysis would probably show that some moisture content was still there.

  9. #22
    Join Date
    Nov 2006
    Location
    Southeastern Pa
    Posts
    18,232
    Quote Originally Posted by PMARS2345 View Post
    Check out this video on YouTube of a guy pulling a vacuum on a clear bottle of POE that came out of a new scroll compressor. http://www.youtube.com/watch?v=NzXO8...e_gdata_player
    I think he is drawing the wrong conclusion form his experiment.

    It looks to me like he is able to pull gasses from the oil, not moisture.
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  10. #23
    Join Date
    Dec 2011
    Location
    bedford ind
    Posts
    1,088
    maybe he had too much water in the bottle for such a short time it couldn't all be absorbed.

  11. #24
    Join Date
    Nov 2010
    Location
    MN
    Posts
    144
    Quote Originally Posted by timebuilder View Post
    I think he is drawing the wrong conclusion form his experiment.

    It looks to me like he is able to pull gasses from the oil, not moisture.
    How do you know its not moisture? What do you think it could it be then?

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