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  1. #1
    Apollo10's Avatar
    Apollo10 Guest

    York Chiller startup when on Emergency Power



    Hi everyone, great forum.

    Looking for some insight on our 850 Ton York Centrifugal Chiller.

    I realize there are certain interlocks and protection measures programmed into the control board on these chillers, our building is very dependent on stable process cooling.

    When we have a power loss and the generator fires up, the York Chiller initiates shutdown. There is a minute or so period where it will not allow a reset until the compressor and everything has stabilized off. Then we manually reset it and initiate the restart sequence. Takes about 10 mins overall.

    My question is whether we can decrease the timeline where the chiller shuts down and restarts up to full load again.

    Ours runs at 40% for 5-10 mins and then incrementally goes up to 100%. The cooling load usually increases dramatically during this transition period and takes a while to get back within specs (41.0F cooling supply).

    Is there a way to have the chiller ramp up to 100% once the initial 40% start-up/warm-up period is over?

    Or decrease the time it stays at 40% since the chiller intself is already warm / at operating temperature?

    Any suggestions, or is this even possible?
    FYI, the unit has a VFD, we have the limit set to 100%.



  2. #2
    Join Date
    Aug 2007
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    Re: York Chiller startup when on Emergency Power

    Does VFD mean VSD (Variable Speed Drive)? The anti recycle timer is set that the motor is prevented from overheating due to excessive chiller cycling. But when the motor starts again, the chiller will ramp up to 100% depending on the deviation between leaving chilled water temperature and chilled water set point. On YK it takes approximately 12min. from starting command until the chiller reaches full load. I suspect that you have a load limiting programmed into the control to allow the system to stabelize and prevent it from low suction pressure cut outs. The pull down limit as it is called can be disabled in the software as well as the software can be set to automatic restart after power failure. Then it is not required to manually reset the chiller. You should ask your local York engineer for further support.

    regards,
    Entropie

  3. #3
    Apollo10's Avatar
    Apollo10 Guest

    Re: York Chiller startup when on Emergency Power

    Yes VSD, (sorry I've been with Air handlers for the last little while)

    Thank you for you input, extremely helpful. I will consult with our Chiller tech on getting things adjusted.

  4. #4
    Join Date
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    Re: York Chiller startup when on Emergency Power

    If your load is that sensitive , the system should have a buffer tank sized to at least (flow rate x length of time from off to 100%fla).
    YK s have a 2min coastdown, and 45 sec prelube.
    If it goes off on a power fault i think you have a standard 20 min delay before restart. (that maybe changeable by dip switch)
    The ramp speed may be affected by the VSD control trying to keep out of a surge condition stored in the surge map. Surge map may have things in there that dont relate to your circumstances today ie. when commisioned you didnt have the same base load on the machine as you do today. thats all i will say about that. I wouldn't be in a hurry to alter settings, if you have frequent power outages, take it up with the utility company, dont tweak an 850 ton chiller to get back in spec quicker.If its a priority to have that even temp- Buffer tank!
    Hope that helps

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