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  1. #1
    Join Date
    Sep 2014
    Location
    NH
    Posts
    15

    The relationship between oil and refrigerant?? Help a new guy.

    Hello all,

    I've just started in HVAC as an install helper, and am currently studying for my EPA test.

    I'm having a hard time understanding how oil fits into a system.

    Is oil mixed with the refrigerant and cycles through the condenser and evaporator back to the compressor? Is the oil separate from the refrigerant? If separate, what keeps the oil at the compressor and not just pool at the lowest point in the system?

    When you recover a system does the oil come out with it? Does it depend on liquid or vapor recovery? If the oil does come out, how is it replaced when you recharge the system?

    Sorry for the rapid fire questions, I just can't seem to get my head around how this works.
    I'm hoping someone can fill in the gap for me.

    Thanks

  2. #2
    Join Date
    Mar 2009
    Location
    Triad - North Carolina
    Posts
    444
    Co-habitation
    Yes, I've seen that before and it doesn't mean I like it.

  3. #3
    Join Date
    Aug 2014
    Location
    Vancouver, Britsh Columbia
    Posts
    16
    http://www.rses.org/assets/serviceap...l/620-1071.pdf

    This is a good resource on how oil behaves in a system, just try not to get caught up in the technical stuff.

  4. #4
    Join Date
    Aug 2012
    Posts
    2,755
    If oil migrates out of the compressor it will be a problem unless you have traps to return it. If recovering you could suck some out if it is just pooling around the connectors. other than that oil will atomized and travel thru the system with the freon. Migration is an issue that needs attention however.
    My name is TooCoolforschool and I am a chronic over charger.

  5. #5
    Join Date
    Nov 2014
    Location
    Socal
    Posts
    3
    Is oil mixed with the refrigerant and cycles through the condenser and evaporator back to the compressor? Is the oil separate from the refrigerant? If separate, what keeps the oil at the compressor and not just pool at the lowest point in the system?

    Oil is miscible with refrigerant, although it is not mixed at the beginning as the system cycles this action naturally happens. Oil will pool at the lowest point of the system, that is where line sizing comes into play. The velocity of the refrigerant has to remain at a certain point to return it to the compressor. A incorrectly sized system will have velocity too low and allow oil to pool at low points in the piping. A system with velocity too high will cause excess noise and strain on the compressor.

    When you recover a system does the oil come out with it? Does it depend on liquid or vapor recovery? If the oil does come out, how is it replaced when you recharge the system?

    Depends on the system. Some of the oil will come out with the refrigerant on recovery, but not usually a substantiation amount. Some compressors have the ability to add oil if it is needed but certainly not seal hermetic compressors.

    Wouldn't life be easier if there was some kind of oil free compressor

  6. #6
    Join Date
    Jan 2010
    Posts
    6,838
    Quote Originally Posted by Dougxfresh View Post
    Wouldn't life be easier if there was some kind of oil free compressor
    Ahhh....that would be the Turbocor Compressor.

  7. #7
    Join Date
    Oct 2014
    Location
    Columbus, Ohio
    Posts
    221
    Quote Originally Posted by VTP99 View Post
    Ahhh....that would be the Turbocor Compressor.
    Yeah too bad that's not available in a smaller size suitable for DX applications. As it is, I would love to see a scroll where the motor is separate so that acid won't damage the windings and kill the motor. But it seems like they only want to make them as a hermetic package, which kind of sucks in my opinion.

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