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  1. #1
    Join Date
    Jul 2010
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    Trinidad
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    3

    YCAS Slide valve problem?

    Hi guys. I'm also looking into some problems on a YCAS300 unit...like others I'm having trouble with the slide valve, yet unlike the pointers in the bulletin my problem is slightly different.

    The SV = 0 ( hence closed) yet the %FLA is 91%, thus I would assume the compressor is working at full load. At the same time we are still having issues with cooling.

    Could this infact mean the valve is fully open?

    Thanks for your help.

  2. #2
    Join Date
    Sep 2008
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    Western PA
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    25,671

  3. #3
    Join Date
    Mar 2011
    Location
    East Coast FL
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    1,058
    SV = 0 simply means the micro control is calling for an unloaded compressor.

    The actual position of the valve and loading of the compressor should be determined by a qualified technician.

    A micro reading of 91% FLA could indicate a fully loaded compressor.

  4. #4
    Join Date
    Jul 2010
    Location
    Trinidad
    Posts
    3
    Thanks for your input AiResearch...

    I have called the Technicans yet they are yet to solve my problems (he looked at the %FLA and said it's at full load, yet the unit is still not pulling down to 44-46*F, which could normally be achieved with what is running i.e.253 tons of cooling)

    If the temperature error is +ve, and the rate of cooling is either zero or +ve, then the micro controller is suppose to increase the current to the slide valve, thus it increases from 0 to eventually 75.

    At the same time, it is also noted that the suction superheat is very low (-1*F - 1*F). Wouldn't the a low superheat value occur if the refrigerant flow to the TXV is reduced (I'm assuming that the slide valve, restricts the flow as well?)

    I'm not a york/chiller specialist, just a young AC engineer trying to get a building cooled.

    Thanks for your help guys

  5. #5
    Join Date
    Jun 2006
    Location
    New Jersey
    Posts
    4,337
    Quote Originally Posted by CJ868 View Post
    Thanks for your input AiResearch...

    I have called the Technicans yet they are yet to solve my problems (he looked at the %FLA and said it's at full load, yet the unit is still not pulling down to 44-46*F, which could normally be achieved with what is running i.e.253 tons of cooling)

    If the temperature error is +ve, and the rate of cooling is either zero or +ve, then the micro controller is suppose to increase the current to the slide valve, thus it increases from 0 to eventually 75.

    At the same time, it is also noted that the suction superheat is very low (-1*F - 1*F). Wouldn't the a low superheat value occur if the refrigerant flow to the TXV is reduced (I'm assuming that the slide valve, restricts the flow as well?)

    I'm not a york/chiller specialist, just a young AC engineer trying to get a building cooled.

    Thanks for your help guys
    This just one compressor? What are the other two doing? What vintage machine......TXV's or EEV's? What is your LWT and EWT? Refrigerant flow reduction, increases SH.

    Also, when diagnosing always verify pressures, temperatures, voltages, and amperages with your tools........don't rely on the micropanel readings.

  6. #6
    Join Date
    Jan 2009
    Location
    Jersey
    Posts
    126
    was the %fla verified with a meter, some of the old YCAS weren't set up correctly with the ct's and the calculations.

  7. #7
    Join Date
    Jul 2010
    Location
    Trinidad
    Posts
    3
    Hey guys thanks for the input...had a quick glace at the system today after going through the IOM, and realise it is not a problem with the valve at all! The system is doing what it's been programmed to do, that is to safe guard the compressors when conditions are not right.

    The discharge cut off pressure is 350psi, but the unload pressure is 285...the system was running at 275 - 290, thus it would never load no matter how high the CHLT was ( which was evidently 60*F ). On another compressor the %FLA was too high , 97%, the SV unloads to zero at 100%FLA.

    Seems the unit needs a well deserved servicing (its 1 mth overdue) and for some other issues to be checked.

    I will meet with the technicians and update you guys on the progress.

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