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  1. #27
    Join Date
    Jul 2011
    Location
    Lehigh Valley, PA
    Posts
    427
    The gas condenses to a liquid...pressure collapses and stays that way. The condenser fills with liquid. There is no transfer of heat in the evaporator. Talking single/dual cap tubes & refrigeration circuits.
    Two pages to discuss this, I'm out.

  2. #28
    Join Date
    Jul 2013
    Posts
    63
    Quote Originally Posted by Frostmonkey74 View Post
    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!
    Stand corrected. I guess I was thinking more of a major restriction with a unit with a high pressure switch.

  3. #29
    Join Date
    Jun 2012
    Location
    Wisconsin
    Posts
    118
    if you wanna know if your cap tube is plugged look for frost..... The refrigerant will release its pressure and the temp of the refrig will drop inside of the cap tube. Think a mini cap tube inside of a cap tube

  4. #30
    Join Date
    Oct 2009
    Location
    Raleigh, NC
    Posts
    794
    Quote Originally Posted by Bseliger View Post
    if you wanna know if your cap tube is plugged look for frost..... The refrigerant will release its pressure and the temp of the refrig will drop inside of the cap tube. Think a mini cap tube inside of a cap tube
    Greater than 90% of the time cap tubes become restricted (today) along their entire length with buildup on the walls of the tube. You won't find any frost.

  5. #31
    Join Date
    Sep 2002
    Posts
    2,728
    Next time you pump down a system,watch the high side,does it go up or down?

  6. #32
    Join Date
    Sep 2002
    Posts
    2,728
    Just saw frostmonkes post, I am with him,less heat taken in less to reject! But a high discharge temp,with a restriction, due to high superheat.

  7. #33
    Join Date
    Jun 2013
    Location
    NORTHERN
    Posts
    989

    refer or rfg

    Quote Originally Posted by bwd111 View Post
    ... if refer .. so pressure would ...
    DROP as seen on a beach once in Clearwater; -true! i did not inhale, but they were no i did not spellcheck.


    rfg

  8. #34
    Join Date
    Jun 2013
    Location
    NORTHERN
    Posts
    989
    Quote Originally Posted by coolperfect View Post
    Next time you pump down ...
    if pumping into the cdsr, it changes - higher only a little, enough to fill the cdsr.

    eh?

  9. #35
    Join Date
    Jul 2013
    Posts
    63
    Quote Originally Posted by coolperfect View Post
    Next time you pump down a system,watch the high side,does it go up or down?
    Stupid question. If you're pumping a system down, you close the liquid port and pull in through the suction. Then close your suction. Your head is obviously going to go down because you're reading the pressure in the line set and you're pulling it in. Right? I know I was wrong earlier. I don't get what you're trying to say now.

  10. #36
    Join Date
    Sep 2002
    Posts
    2,728
    Quote Originally Posted by Tommyz23 View Post
    Stupid question. If you're pumping a system down, you close the liquid port and pull in through the suction. Then close your suction. Your head is obviously going to go down because you're reading the pressure in the line set and you're pulling it in. Right? I know I was wrong earlier. I don't get what you're trying to say now.
    High Side would be on the DSV ,no closing of suction,So in effect the king valve is a restriction!

  11. #37
    Join Date
    Jul 2011
    Location
    Nanaimo,BC, Canada!
    Posts
    346
    When you pump a system down by front seating the king vale on the receiver the gauge port on the king valve is still on the high side if the system. ( refrigeration condensing unit not AC/heat pump unit) so there for is still sensing high side pressure..

  12. #38
    Join Date
    Jun 2013
    Location
    NORTHERN
    Posts
    989
    What FM said!

  13. #39
    Join Date
    Oct 2004
    Location
    Central WA
    Posts
    1,497
    So, I heard somewhere that refrigerant has a PT relationship when liquid and vapor is present. So whether you have 1 lb or 30 lbs of R22 in a bottle the pressure at a given temp will be the same, and whether you have a little or a lot of liquid in a condenser coil the pressure at a given temp will be the same as well...

    Also, I had an instructor years ago always saying "heat is pressure." Technically kind of a misnomer, yes, but it takes you back to basics and has always stuck with me. If your metering device is restricted you are starving the evaporator, and thus not picking up heat. If you are not absorbing heat your pressures will be low.

    And.. although you are stacking liquid in the condenser, don't be fooled by a lack of crazy subcooling. Your head pressure (and therefore SCT) is low, remember, and the liquid line temp cannot go below ambient no matter how much refrigerant is behind it.

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