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  1. #27
    Join Date
    Aug 2012
    Location
    Palmyra, Missouri, United States
    Posts
    224
    Key fact that ive learned in charging txv systems and fixed metering. BE PATIENT. .ADD SLOWLY

  2. #28
    Join Date
    Jul 2012
    Location
    Kansas
    Posts
    78
    It's hard to be patient when the sweat is overflowing from your britches because your butt crack can't drain it fast enough.

  3. #29
    Join Date
    Jul 2012
    Location
    Western KY
    Posts
    1,221
    Quote Originally Posted by zxcb View Post
    It's hard to be patient when the sweat is overflowing from your britches because your butt crack can't drain it fast enough.
    Amen!!

  4. #30
    Join Date
    Feb 2008
    Location
    California
    Posts
    2,066
    Guys, this is getting out of control

    Charging a system with a receiver to a certain amount of subcooling is 100% wrong.

    On a system with a receiver it is MUCH more important to maintain a liquid level in the receiver during all operating conditions. The subcooling value is what it is.

    The only way you can manipulate the subcooling to a higher value would be to add enough refrigerant to fill the receiver 100% and overflow into the condenser.

    At which point, you have just grossly overcharged the unit.

  5. #31
    Join Date
    Feb 2008
    Location
    California
    Posts
    2,066
    Since your system has a head pressure control valve.

    You want to charge the system to a clear liquid sight glass.

    Then add the required calculated additional flooding charge.

    It's all about maintaining a liquid level in the receiver during all operating conditions, not subcooling.

    http://www.sporlanonline.com/90-30-1.pdf


  6. #32
    Join Date
    Jul 2000
    Location
    Guayaquil EC
    Posts
    10,392


    If you believe adding refrigerant to a system with a receiver will increase subcooling, then you don't understand why it works for a system without a receiver.

  7. #33
    Join Date
    Aug 2012
    Location
    Palmyra, Missouri, United States
    Posts
    224
    Confused

  8. #34
    Join Date
    Jul 2000
    Location
    Guayaquil EC
    Posts
    10,392
    Quote Originally Posted by icemeister View Post


    If you believe adding refrigerant to a system with a receiver will increase subcooling, then you don't understand why it works for a system without a receiver.
    Quote Originally Posted by drife678 View Post
    Confused
    If you have a typical residential A/C system with a TXV, you already know that if you add refrigerant the subcooling will increase...and similarly, if you remove some the subcooling will decrease.

    But why does this happen? What actually creates subcooling?

    Consider what a condenser coil does. It first desuperheats the discharge gas from the compressor, then it condenses that gas to a liquid at saturation and finally it further cools that saturated liquid to a subcooled state.

    The key to understanding subcooling here is to realize that subcooling is a simple process of heat transfer from liquid refrigerant to the ambient air. How much subcooling you will get is determined by how much of the condenser coil is filled with liquid refrigerant...ie, more liquid/more subcooling and vice versa. This is called stacking liquid in the condenser.

    "OK...So if I add more gas, the subcooling increases because there more liquid stacking up in the condenser coil. What's the difference between that and a what happens in a system with a receiver installed?"

    The receiver is connected in the liquid line leaving the condenser coil. It's purpose is to ensure a steady supply of liquid to the TXV as well as to contain excess refrigerant in the system. It allows the condenser coil to freely drain into it, so no stacking of liquid can occur. Any added refrigerant goes into the receiver. No stacking means no increase in subcooling. The amount of subcooling is fixed at whatever the condenser gives you...which is typically around 5F or so.

    If anyone doubts this, please find a system with a receiver, add some refrigerant and watch what happens to the subcooling as you add it.

  9. #35
    Join Date
    Oct 2011
    Location
    Chicagoland Area
    Posts
    4,639
    Quote Originally Posted by Phase Loss View Post
    Guys, this is getting out of control

    Charging a system with a receiver to a certain amount of subcooling is 100% wrong.

    On a system with a receiver it is MUCH more important to maintain a liquid level in the receiver during all operating conditions. The subcooling value is what it is.

    The only way you can manipulate the subcooling to a higher value would be to add enough refrigerant to fill the receiver 100% and overflow into the condenser.

    At which point, you have just grossly overcharged the unit.
    What level should I maintain the sweat in my buttcrack?
    Officially, Down for the count

    YOU HAVE TO GET OFF YOUR ASS TO GET ON YOUR FEET

    I know enough to know, I don't know enough
    Liberalism-Ideas so good they mandate them

  10. #36
    Join Date
    Feb 2008
    Location
    California
    Posts
    2,066
    I like to run mine around 0% during all conditions.

  11. #37
    Join Date
    Jun 2010
    Location
    Miami
    Posts
    258
    Hey we have all been new and didn't know all the answers at some point. It is tough when your boss throws you the responsibility for something you don't understand. The guy sounds like he knows the basics and is trying to do the right thing. I'm not the most qualified but but I'll try. Plus, being that I'm a maintenance guy, at a hospital, and see truly strange systems, I can relate some.

    So yes, depending on what the system is, a clear sight class under some given condition does not equal a properly charged unit under all conditions. You mention a headmaster and a reciever. That means just subcooling isn't enough and you must do the math and calulate your extra chage per instructions. The only possible short cut would be to revisit the system in winter and add freon to get a clear sight glass.

    That would assume everything is adjusted right and working as it should be. Based on my experience that is the biggest mistake one can make. You never know what those before you have done in an attempt to make something work and please a boss. So (IMHO) this would be a poor way to approach the situation. You have been given a chance to learn something and advance yourself. Grab the bull by the horns and do the right thing. Everyone feels pressured to tell the boss "I can fix it". I can tell you ...from being the boss to the repair guy....it is better to fess up and say "I don't know but I'm going to do everything in my power to learn why".

  12. #38
    Join Date
    Aug 2012
    Posts
    18
    Quote Originally Posted by Russ57 View Post
    Hey we have all been new and didn't know all the answers at some point. It is tough when your boss throws you the responsibility for something you don't understand. The guy sounds like he knows the basics and is trying to do the right thing. I'm not the most qualified but but I'll try. Plus, being that I'm a maintenance guy, at a hospital, and see truly strange systems, I can relate some.

    So yes, depending on what the system is, a clear sight class under some given condition does not equal a properly charged unit under all conditions. You mention a headmaster and a reciever. That means just subcooling isn't enough and you must do the math and calulate your extra chage per instructions. The only possible short cut would be to revisit the system in winter and add freon to get a clear sight glass.

    That would assume everything is adjusted right and working as it should be. Based on my experience that is the biggest mistake one can make. You never know what those before you have done in an attempt to make something work and please a boss. So (IMHO) this would be a poor way to approach the situation. You have been given a chance to learn something and advance yourself. Grab the bull by the horns and do the right thing. Everyone feels pressured to tell the boss "I can fix it". I can tell you ...from being the boss to the repair guy....it is better to fess up and say "I don't know but I'm going to do everything in my power to learn why".
    Thanks that is what I am trying to do at this point. I will read and calculate the additional charge required and go from there. All this assuming there is not a leak I have not found. Be back out there this moring and snoop around again with the UV light before doing anything else.

  13. #39
    Join Date
    Aug 2012
    Location
    willowick ,oh
    Posts
    261
    Any system with a reciever will use signifigantly more refrigerant. Ive made it a habit to recheck when the box is down to temp.

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