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  1. #14
    Join Date
    Jul 2007
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    Mount Airy, MD
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    Quote Originally Posted by Heritage MT View Post
    Yes u too
    You have 4 more to go

  2. #15
    Join Date
    Jan 2004
    Location
    Lancaster PA
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    68,058
    Quote Originally Posted by Rcb2875 View Post
    The short answer,
    Systems with TXV's use sub cooling because the TXV tries to keep a constant designed SH.
    You charge fixed, orifice systems by Sh to make sure the liquid line is full of liquid and not boiling off before the orifice.

    Both measurements are very important to a systems health and diagnosis but this is the basics of it.

    Not exactly correct, but getting close.
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  3. #16
    Join Date
    Jan 2004
    Location
    Lancaster PA
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    68,058
    Quote Originally Posted by Chris_Worthington View Post
    You have 4 more to go
    Chris is a very patient person( I think its a requirement to be a good controls guy ), I on the other hand am a very gruppy person.

    Get that post count up fast. LOL
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  4. #17
    Join Date
    Oct 2010
    Location
    oregon
    Posts
    46
    I understand the difference on fixed orfice/ superheat vs txv/ sub cooling now just takes me a minute or two to think about how the refrigeration systems works and the txv and how it affects the system. Thanks for the help guys

  5. #18
    Join Date
    Oct 2010
    Location
    Baton Rouge, LA
    Posts
    1,113
    A Thermostatic Expansion Valve (TXV) is designed to maintain a constant superheat. Over charging a TXV will rise sub-cooling, increases system pressures, and decreases system efficiency. Under charging a TXV will decrease sub-cooling, increases superheat, decrease system capacity, and lower refrigerant velocity leaving oil in the evaporator.

    A/C with a Thermostatic Expansion Valve (TXV) is charged to the sub-cooling of the liquid line leaving the condenser because the superheat is fixed. Sub-cooling is the amount of liquid held back in the condenser. This allows the liquid to give up more heat, below saturated pressure- temperature.

    Do not worry about a few bubbles in the sight glass. Sight glasses will not always be clear with a full charge. The zeotropes refrigerant group is known for their fractionation. It is possible to never have a clear sight glass. If the sight glass is close to the exit of the condenser or if there is very little sub-cooling at the sight glass, bubbles may be present even when the system is properly charged. If a system is charged to full sight glass, overcharging may be the result, decreasing efficiency.

    I am sure I missed something but beenthere will inform me if I have. I want a gold star if I hit it all.
    If you're too "open" minded, your brains will fall out.
    Artificial intelligence is no match for natural stupidity.

  6. #19
    Join Date
    Jun 2011
    Location
    Hammond,La.
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    1,176
    Quote Originally Posted by beenthere View Post
    Not exactly correct, but getting close.
    Didn't think it was necessary to go into refrigerant stacking, evac coil flooding/starvation, oil circulation, and head pressure vs compressor efficiency. Not to mention a small issue of long line sets and improper head/suction pressure plays in oil circulation. liquid vert Trap or no trap..
    If the liquid line doesn't flood the liquid line to the meter you are losing efficiency from boil off in the line vs the evap where the cooling effect of the boil is needed producing wasted e coil space from spent vapor.
    Anything much more and we will rename the thread HVAC theory 101

  7. #20
    Join Date
    Jan 2004
    Location
    Lancaster PA
    Posts
    68,058
    Quote Originally Posted by Rcb2875 View Post
    Didn't think it was necessary to go into refrigerant stacking, evac coil flooding/starvation, oil circulation, and head pressure vs compressor efficiency. Not to mention a small issue of long line sets and improper head/suction pressure plays in oil circulation. liquid vert Trap or no trap..
    If the liquid line doesn't flood the liquid line to the meter you are losing efficiency from boil off in the line vs the evap where the cooling effect of the boil is needed producing wasted e coil space from spent vapor.
    Anything much more and we will rename the thread HVAC theory 101
    if you ever get pro status. we'll go over what you were close to in the other post.
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  8. #21
    Join Date
    Jun 2011
    Location
    Hammond,La.
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    Quote Originally Posted by beenthere View Post
    if you ever get pro status. we'll go over what you were close to in the other post.
    Coming soon...

  9. #22
    Join Date
    Mar 2006
    Location
    Denver/Boulder
    Posts
    2,286
    Waaay too much DIY fodder, IMO.


    School is in session on the other side for some of those posting.
    What lies behind us and what lies before us are small matters compared to what lies within us.


    Two pressures, four temperatures = SUCCESS!


    Boulder Heating Contractor


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    For HVACR Professionals:


  10. #23
    Join Date
    Jun 2011
    Location
    Utah
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    15
    I thought you only needed 15 posts to apply for the pro side. what else is required.

  11. #24
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    Jul 2007
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    Mount Airy, MD
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    Quote Originally Posted by jdaugrefer View Post
    I thought you only needed 15 posts to apply for the pro side. what else is required.
    Perhaps this will help http://hvac-talk.com/vbb/showthread.php?t=703121

  12. #25
    Join Date
    Dec 2002
    Location
    SouthEast NC ICW & Piedmont Foothills
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    7,635
    Quote Originally Posted by jdaugrefer View Post
    I thought you only needed 15 posts to apply for the pro side. what else is required.
    there are several:

    tequila

    $39.99

    i'm forgetting something.............................
    It`s better to be silent and thought the fool; than speak and remove all doubt.

  13. #26
    Join Date
    Jun 2011
    Location
    Utah
    Posts
    15
    was that tequila with or with out the worm?

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