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Thread: YMC2 york chiller - "evaporator - low pressure" Fault

  1. #1
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    YMC2 york chiller - "evaporator - low pressure" Fault

    Suddenly, i got this fault on YMC2 chiller: "evaporator - low pressure" and system doesn't run anymore.

    2 min after starting it, it surges, shuts down and shows "evaporator - low pressure" fault.

    I haven't found any refrigerant leak.

    Expansion valve is actuating.

    Enough water flow rates. Inlet chilled water and condensing water temperature are correct.

    Any thoughts?

  2. #2
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    Did you verify the transducer is reading correctly?

  3. #3
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    Verify transducer is reading correct.
    Verify your leak detector is working.
    Take your water pressure drops with only one gauge, pressure drop on sales order screen is in feet water column not PSID.
    Could be divider in water box has failed or evaporator tubes are dirty.


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  4. #4
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    Did you check the variable flow actuator and the liquid level sensor

  5. #5
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    Level in condenser? VGD moving?

  6. #6
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    Upload a history log for us to look at ?

  7. #7
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    Thread Starter
    - Pressure transducer reading is good;
    - I've used same manometer for water pressure drop;
    - Leak detector is working
    - There is no variable flow actuator
    - VGD is moving

    But....

    Today i've checked condenser level sensor. No good news.

    I've set level control valve to MANUAL and I was able to start it and get it running. I had stable operation at 30% level control valve command. Anything below 30% and condenser level got high, visor got 100% filled and chiller started to surge.

    However, I have two chillers running in parallel. Parameters below were taken when they both were at 55% input load, 13C CWET, 7C CWLT.

    Chiller A, which is working properly:
    -Active level setpoint = 46%
    -Condenser refrigerant level = 46,8%
    -Condenser refrigerant visor at about 25%
    -Level control valve command = 23% (automatic mode)

    Chiller B, which is the subject of this matter:
    -Active level setpoint = 35%
    -Condenser refrigerant level = 10,1%
    -Condenser refrigerant visor at about 50%
    -Level control valve command = 31,2% (manual mode)

    As we can see, condenser liquid level sensor from chiller B is not reading correctly, as it reads only 10% when actual level is higher than chiller A which has 45% reading.

    I operated chiller B like this for like 2hrs. At the moment i set the valve back to auto, valve was closing and it started to surge and shutdown.

    Anything I can do other before replacing liquid level sensor?

    ive uploaded some pictures.

    PS.: As you can see, march 30th i got low pressure warning as well, but its not related. operator closed chilled water valve with chiller running.
    Attached Thumbnails Attached Thumbnails 20200403_170151.jpg   chiller A.jpg   Chiller B visor.jpg   chiller b.jpg   history log.jpg   chiller B - system.jpg  

  8. #8
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    Aug 2019
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    U can try to recalibrate but I would think it will not work. Replacement should be easy. Just set 0 before u add refrigerant back.

  9. #9
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    Mar 2015
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    I would try to calibrate it first. https://docs.johnsoncontrols.com/chi...YrMgBWZPWVI5Mg

  10. #10
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    If you need the chiller on line drive the liquid level control valve to open and pull the electrical connector off the valve , power loss will but valve back to auto. Other wise get the tech letter on how to calibrate , if it will not calibrate just the head can be replaced and get you on line.


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  11. #11
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    There is a 30 page tech letter that covers all the styles. It has part numbers in it.


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  12. #12
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    Aug 2019
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    I would not pull power from valve actuator, that is a falling film evaporator. If the refrigerant level is to high in evaporator it could cause much worst issues.

  13. #13
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    Let him know why.


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  14. #14
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    Aug 2019
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    Your can cause carry over and loss of liquid seal

  15. #15
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    Loss of liquid seal alarming is now ignored below 40% FLA with the new software. To eliminate false warnings. It was found that the loss of seal at low loads has no ill effect.


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  16. #16
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    Aug 2019
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    LA
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    True but force the refrigerant in to the evaporator and run the condenser dry will have I’ll effects.

  17. #17
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    Mar 2018
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    Thread Starter
    Anybody could share the link to sensor callibration?

    Do I need to change all the sensor or only part of it?

  18. #18
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    I could email you the document but your email is not in your profile

  19. #19
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    Thread Starter
    i've attached a photo of the sensor board.
    Attached Thumbnails Attached Thumbnails WhatsApp Image 2020-04-07 at 2.46.10 PM.jpeg  

  20. #20
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    Thread Starter
    i've updated my profile with my email

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