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  1. #1
    Join Date
    Oct 2003
    Location
    tidewater, va
    Posts
    2,147

    Mcquay bailout needed

    Not for the company...for the tech!

    Mcquay gurus:
    Don't see many of these around here. Got a Mcquay centrifugal, Model PEH087-AAAB, ser#57B81025-00 Style: 9641925010 Appears to be 200 series panel. Trouble with the unit was that it was in alarm, that alarm being "no 5volt DC signal to Sensor #19" Long story short, the Analog input was not seeing 5 volts DC. I pulled and checked the connector at the analog input, pressing in the wire harness and even replaced the connector and was able to get the machine online and it would run for 20, 30 minutes or so and i watched the signal drop to 4.5 volts and it kicked out, same fault. I assume something is dragging it down.
    Couple of questions: first, Why is Sensor 19 listed as the Transducer Power Voltage Ratio? Is sensor 19 just an actual input status? All transducers are feeding back, I just seem to be dragging the power signal down.
    I am lucky enough to have another machine onsite and am probably going to try to swap out the MCB to beggin with. i did monitor this other unit and noted that it had a steady 4.9 vdc signal. Any input on testing these modules? thanks in advance.


    r404a

  2. #2
    Join Date
    Feb 2003
    Location
    Wichita Ks
    Posts
    1,507
    have you checked the connector at the mcb where the 5vdc comes out? also check and trace the wire all the way. if it goes to a terminal strip with factory jumpers pull the jumpers and check condition. check all sensor connections. if you have more than one meter I would connect it in several places and watch it and see where it is dropping.

  3. #3
    Join Date
    Oct 2007
    Location
    Arizona DUH
    Posts
    174
    Yeah I have the SAME problem on a screw chiller. Cant find it anywhere. I even changed out the board and still can't find it. I too would like to know.

  4. #4
    Join Date
    May 2001
    Location
    Western Wa
    Posts
    1,864
    http://www.mcquay.com/mcquaybiz/lite...OM200MICRO.pdf

    Sensor 19 is just a place they measure DC voltage.
    Sometimes you'll see this after a power outage, or when you power up the panel.

    I'd be for trying to figure out if a sensor or wiring is pulling down the DC voltage.
    Like maybe metering the DC while you lift sensor wires pair by pair.
    God Bless our Veterans

    God Bless the USA

  5. #5
    Join Date
    Oct 2003
    Location
    tidewater, va
    Posts
    2,147
    randy and rick

    thanks for the input, you guys always help. I think this one is going to be a B#$%h. But I guess if they were all easy...everyone would be doing it...thanks again


    r404a

  6. #6
    Join Date
    Oct 2003
    Location
    tidewater, va
    Posts
    2,147
    thought I had this earlier, because I could'nt reset the fault until I pulled the cover off the connector at the AI board and depressed the connector further into the knife blade. I evan replaced this connector wih a generic one I had to be sure connection was good. rick, any word on a part number for the original red connectors? i will check these items. Thanks again.

    r404a

  7. #7
    Join Date
    Feb 2003
    Location
    Wichita Ks
    Posts
    1,507
    I have not been able to locate the part number on the parts break down. I gave my office one to locate a couple of weeks ago. I have seen them as generic before. I will need to search again for them.

  8. #8
    Join Date
    Jan 2008
    Location
    windy city
    Posts
    4,444
    had to find my parts breakdown. found no reference to 'connectors' in peh087 rev.g 2/01 form rpl057110700 pg.38. also pg 40 has a breakdown of sensors - no mention of sensor 19, goes from 18 to 20 on up.

  9. #9
    Join Date
    Jun 2009
    Location
    Florida
    Posts
    540
    Sorry to semi-hijack the thread, but I have a PFH063 that I take care of (and which I'm not too familiar with) and haven't seen for a couple months since I did the quarterly on it. The owner called me today and said they are having issues with it restarting after power brownouts, surges, etc. He calls them "power bumps". I asked him to go look at the diagnostic the microtech is giving him and call me back. It is latching on Low Motor Current, which by my understanding, is that it is trying to restart with no line current to the solid state starter. I think it only has power to the controls and times out after not starting for 30 seconds. I don't have a lot of info on what's really going on, but need to get a little better educated on what happens on a McQuay when it goes into low motor current before I walk into a hornets nest. Is it possible that his controls might be on generator power, but not the main to the starter? It's a hospital with one chiller and it's happening early in the morning when no facilities guys are on staff. By the time they catch it and clear the diagnostic, the chiller has been down for a couple hours.

    Any help would be appreciated.

    CW
    Low Pressure Forever!

    If you know heavy metal, you can work anywhere-Dave Andreson

    Anchors Aweigh my boys, Anchors Aweigh!
    Farewell to foreign shores, We sail at break of day. Through our last night on shore, Drink to the foam. Until we meet once more. Here's wishing you a happy voyage home!

  10. #10
    Join Date
    Jan 2008
    Location
    windy city
    Posts
    4,444
    not that familiar on mcquay, but the ones i've been on get their control voltage after the disconnect. dug out the disc - can't open the index. what vintage, which control panel

  11. #11
    Join Date
    Oct 2007
    Location
    california
    Posts
    57
    ChillerWhisperer

    Hey in the process of same failure right now. If its a microtech 100 it could be several things..... it gets it current sensing from dc/dc converter there is a svc. bullitin out stating to install 10mfd capacitor across dc/dc converter for certain vintage, or possibly be bad or failing MCR's or fault or failing Aux contact on M2 contactor. I recently spoke w/ stickerhead about this and he maybe suggested that it could be a faulty or failing relay on relay board for unit start/stop or if it has a phase monitor possibly there..ours is failing intermittently and watch it with no problems and I can not reproduce it when i'm on site. good luck...

    R404 sorry not trying to change subject..

  12. #12
    Join Date
    Oct 2003
    Location
    tidewater, va
    Posts
    2,147
    appreciate the input


    r404a

  13. #13
    Join Date
    Jun 2009
    Location
    Florida
    Posts
    540
    The one I'm working on was started in 95. That would make it a microtech 100, correct?
    Low Pressure Forever!

    If you know heavy metal, you can work anywhere-Dave Andreson

    Anchors Aweigh my boys, Anchors Aweigh!
    Farewell to foreign shores, We sail at break of day. Through our last night on shore, Drink to the foam. Until we meet once more. Here's wishing you a happy voyage home!

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