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  1. #1
    Join Date
    Nov 2015
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    McQuay WDC126 "Low Net Oil Pressure"

    Hi guys, My name is Miguel, Im from Bolivia and Im new in this forum . I have a problem with a Chiller McQuay model WDC 126, its a Chiller with 2 compressors, each compressor works with a independent lubrication system... my problem its just with 1 of them. The problem is the pressure in the system, during the pre lub and post lub the feed pressure is about 134 psi but in the good compressor the same pressure reaches about 234 psi. I changed the filters and tested the sensors but the problem continues. What else can I check? apparently the pump its ok and the lvl oil its ok too.

    Thx in advance, regards.

  2. #2
    Join Date
    Jun 2008
    Location
    Windsor, Ont.
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    Hi Miguel and welcome to the forum. The feed pressure seem a little high assuming this chiller is using R134A, typically McQuay runs a net oil pressure of 100 psi which is the difference between sump pressure and feed pressure. Unless your refrigerant pressure is above 100 psi during prepurge 234 psi is high in my mind. I assume you have verified that the oil pump is actually starting and that the feed pressure rises during prepurge.

    Alternatively there are a number of possibilities I can think of 1. Failed pressure Regulating Valve, 2. Failed oil pressure transducer, 3. Failed Oil Pump, 4. Internal sump leakage at various fittings and 5. Compressor bearing failure.

    As far as how to check for these possibilities I will not make further comments here in the open forum and can only wish you good hunting.

  3. #3
    Join Date
    Apr 2011
    Location
    Southern Indiana
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    Do you know what would cause a Low Oil Delta Pressure?

  4. #4
    Join Date
    Apr 2011
    Location
    Southern Indiana
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    Quote Originally Posted by nyrb View Post
    Hi Miguel and welcome to the forum. The feed pressure seem a little high assuming this chiller is using R134A, typically McQuay runs a net oil pressure of 100 psi which is the difference between sump pressure and feed pressure. Unless your refrigerant pressure is above 100 psi during prepurge 234 psi is high in my mind. I assume you have verified that the oil pump is actually starting and that the feed pressure rises during prepurge.

    Alternatively there are a number of possibilities I can think of 1. Failed pressure Regulating Valve, 2. Failed oil pressure transducer, 3. Failed Oil Pump, 4. Internal sump leakage at various fittings and 5. Compressor bearing failure.

    As far as how to check for these possibilities I will not make further comments here in the open forum and can only wish you good hunting.
    Where is the pressure regulating valve located?

  5. #5
    Join Date
    Aug 2000
    Location
    Under my tree
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    Its on top of the sump.
    Quote Originally Posted by SanchezHVAC View Post
    Where is the pressure regulating valve located?
    To much work with too little time!!!!

  6. #6
    Join Date
    Nov 2004
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    up in the hizzy
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    Quote Originally Posted by SanchezHVAC View Post
    Do you know what would cause a Low Oil Delta Pressure?
    possibly a bad second stage seal
    There is not better place for the working men than the union! 100% UA the only HVAC union!

  7. #7
    Join Date
    Apr 2011
    Location
    Southern Indiana
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    Quote Originally Posted by valdelocc View Post
    possibly a bad second stage seal
    I don't know much about these chillers. A bad second stafe seal on what?

  8. #8
    Join Date
    Aug 2009
    Location
    Prattville, Alabama
    Posts
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    The OP has posted a grand total of ONE time. This one. Almost four years ago...
    In honor of RichardL: "Ain't 'None' of us as smart as 'All' of us".

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