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Thread: 4-stage cascade

  1. #51
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    Re: 4-stage cascade



    Quote Originally Posted by before View Post
    I've repaired few small leaks; repaired the second stage TXV and now trying to get it working properly with a mixture of R23 and R1150.

    Any idea on how much pressure is usually used by manufacturers in a TXV bulb?
    In the bulb is mostly the same refrigerant as the circuit it controls. The pressure is that pressure at the corresponding temperature.


    It's better to keep your mouth shut and give the impression that you're stupid than to open it and remove all doubt.

  2. #52
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    Re: 4-stage cascade

    It makes sense. Interestingly, playing with the bulb pressure allows to play with refrigerant charge of the system. For example, it is possible to achieve the same evap temperature with a moderate refrigerant charge but with a high bulb pressure than with more refrigerant in the circuit but with less pressure in the bulb. I've tested this yesterday and I have been able to run a system with less static pressure.

  3. #53
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    Re: 4-stage cascade

    I've removed the 3rd stage CPU evaporator CPEV because it was leaking by the screw, and replaced it by 1.75m of .8mm captube.

    Evap out = -129.3C; it looks fairly accurate.



    HSP: 1st stage at 10.5 bars, 2nd stage at 5 bars and 3rd stage at 13
    Probes gave -50C for the 1st stage TXV and -85C for the 2nd stage TXV.



    I didn't know why, but 3rd stage evaporator took a very long time to go down to about -117C and then lost nearly 20C within few seconds.... I was a bit puzzled. So I've tried different captube lengths to finally switch back to a CPEV.

    Unfortunately, this new CPEV puts more load on the higher stages. 2nd stage R23 is not enough now. I'm considering doing the following:

    - Replacing 1st stage R507 by R410 which would be better to condensate 2nd stage R1150
    - Replacing 2nd stage R23 by R1150 which is needed in order to condensate 3rd stage R14

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