McQuay Novice
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Thread: McQuay Novice

  1. #1
    Join Date
    Oct 2003
    Location
    tidewater, va
    Posts
    2,131

    McQuay Novice

    Techs,
    I have a couple of questions concerning a McQuay chiller, Model# PEH087, Ser#5ya0103500, with a Microtech panel, R134a. The password for the microtech is not recorded on the machine, is there a standard password? The machine is 480 volt 3-phase, 60 hertz. The starter module is an IQ 1000 II.
    I have not had many calls on these McQuay machines so these questions may seem basic. Sorry for the length of the questions. The chiller originally experienced an IOC starter fault, but has also had transition failures. I am scheduling a time to clean and inspect the starter and auxiliary switches.
    Upon checking the starter trip of Instantaneous Over Current (IOC) I megged the motor and with the protective capacitor removed from the motor circuit, got good megger readings, all infinite to ground and between phases. The protective capacitor is rated at 1 mfd and 650 vac. I understand that it is provided for surge protection, but how does it provide that protection?
    Also, does the IOC trip occur only at start up? Or is it anytime over current is experienced? I checked amperage at start up to be sure that the guide vanes were not stuck open and the start up is smooth and transitions rapidly.
    By the time I arrived today, the chiller pump had been running for quite a while with a hot building and I had almost 90 degree evap water temp. The chiller would start but after a minute or so, the chiller would trip on low oil temp, and as I understand it, because the suction saturated temp was so high that it couldn’t maintain the 40 degree differential to oil sump temp. This machine has also been known in the past to fault on high suction temperature during similar HOT pulldown. Is there a way to temporarily bypass these safeties during hot pulldown?
    And finally, a basic mechanical question. It looks like the oil sump vents directly to low stage compressor pressure, after the inlet guide vanes at impeller inlet. How does this allow oil to stay in the sump at start up without a valve in the vent line, at start up?
    Thank you for the time.

    r404a

  2. #2
    Join Date
    Feb 2006
    Location
    SouthEastern Virginia
    Posts
    1,075
    Good grief that's a lot of questions
    It might get loud!

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