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  1. #14
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    Jul 2009
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    new york
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    That is what I read in my system diagnostics and troubleshooting manula than after reading the info on http://www.supco.com/images/pdfs/Man...g%20Manual.pdf website they are saying too much restriction resluts in excessive pressure. But what you are saying is what I was taught so why is supco saying differeant where are they getting all the referigant from

  2. #15
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    Jul 2011
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    Nanaimo,BC, Canada!
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    Effects of capillary tube plugged

    Not sure where supco would be getting their information, nor have I read it. However my statement is based on 20 years experience in the industry.

  3. #16
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    Nov 2006
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    Southeastern Pa
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    The condenser on cap tube systems is small compared to air conditioning systems, so once all the refrigerant backs up in there you could run out of room and have higher pressures.
    [Avatar photo from a Florida training accident. Everyone walked away.]
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  4. #17
    Join Date
    Jul 2013
    Location
    Harrisburg, PA
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    295
    Quote Originally Posted by timebuilder View Post
    The condenser on cap tube systems is small compared to air conditioning systems, so once all the refrigerant backs up in there you could run out of room and have higher pressures.
    That was my original thinking when I made my first reply. So I'm not crazy!

  5. #18
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    Oct 2009
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    Raleigh, NC
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    Quote Originally Posted by timebuilder View Post
    The condenser on cap tube systems is small compared to air conditioning systems, so once all the refrigerant backs up in there you could run out of room and have higher pressures.
    I guess you COULD, but I only see higher than normal head pressure in systems with clogged capillary tubes when someone has added additional refrigerant to attempt to raise suction. If I approach a system that has never had service stubs added, I can usually accurately diagnose a competely clogged cap tube based on temperature of various places. If there ARE service stubs added, all bets are off. It is hard to determine if (most of the time, how much) the charge is off.

  6. #19
    Join Date
    Jul 2013
    Posts
    63
    Any restriction causes high head low suction. It's pumping but can't pull anything back. It's building up head but not bringing it back. To the guy who won't read an article but has the experience, maybe you should read.

  7. #20
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    Jul 2011
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    Nanaimo,BC, Canada!
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    I'd like for you to explain to me how a positive displacement compressor develops head pressure if its not pumping?
    And FYI I read lots but I don't read every piece of literature produced by every manufacturer . Do you?? Didn't think so!

  8. #21
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    Oct 2009
    Location
    Raleigh, NC
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    794
    Quote Originally Posted by Tommyz23 View Post
    Any restriction causes high head low suction. It's pumping but can't pull anything back. It's building up head but not bringing it back. To the guy who won't read an article but has the experience, maybe you should read.
    Nope.

    Can't build up much head with nothing to compress.

  9. #22
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    Jul 2009
    Location
    new york
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    Quote Originally Posted by Frostmonkey74 View Post
    I'd like for you to explain to me how a positive displacement compressor develops head pressure if its not pumping?
    And FYI I read lots but I don't read every piece of literature produced by every manufacturer . Do you?? Didn't think so!
    I with you on this because if refrigerant is backed up in the condenser the high side is feed through the low side if lowside is backed up where is highside getting refer to discharge at higher pressure. I could see higher temp the overload tripping. So question is where is highside getting refer to discharge at higher pressure.

  10. #23
    Join Date
    Sep 2002
    Location
    Virginia
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    Its rare , but you can see higher head pressure with a restriction. Normally , its low , along with the low side being low.

  11. #24
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    Jul 2011
    Location
    Lehigh Valley, PA
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    447
    Quote Originally Posted by Tommyz23 View Post
    Any restriction causes high head low suction. It's pumping but can't pull anything back. It's building up head but not bringing it back. To the guy who won't read an article but has the experience, maybe you should read.
    So...you are the guy before me who overcharged that clogged cap tube system...

  12. #25
    Join Date
    Jul 2013
    Posts
    63
    Quote Originally Posted by Capz View Post
    So...you are the guy before me who overcharged that clogged cap tube system...
    Negative. There are many tests. Are you saying a restriction doesn't cause high head? What happens when a txv slams shut?

  13. #26
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    Jul 2011
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    Nanaimo,BC, Canada!
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    Quote Originally Posted by Tommyz23 View Post
    Negative. There are many tests. Are you saying a restriction doesn't cause high head? What happens when a txv slams shut?
    The same result as when a cap tube plugs.... While the compressor is pumping out the refrigerant in the low side of the system, the head pressure will climb " momentarily" how ever if you were to leave it to run in a vacuum, as you would see with any system with a plugged capillary tube, you wild find the high side pressure would drop as well.. Next time you pump down a system watch your gauges, next time you're working on a ref system set up for pump down watch how it works ... Same principle ... If the compressor isn't moving any refrigerant it cannot develop head pressure!

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