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Thread: Pump Controls not functioning as expected

  1. #1

    Join Date
    May 2014
    Posts
    12

    Pump Controls not functioning as expected

    I am troubleshooting why a pump is not remaining off. Three pumps are set to shut off when the level in a tank hits 113'. One of these pumps continues to turn on unexpectedly. This pump also has controls based on downstream pressure and a VFD setting. However, the results graphs don't make sense given these control points. During the shown time, the tank is full, so all pumps should be off, but pump 1 continues to cycle. Any ideas?
    Capture.JPGcontrols.JPG

    Also here is pump 2 and its controls which correctly shuts off:
    pump2.jpgcontrols2.JPG

    Thanks,
    Ross
    Last edited by RossV; April 12, 2019 at 09:18 AM. Reason: added detail

  2. #2
    Forum Moderator

    Innovyze Employee



    Innovyze Employee



    Join Date
    May 2015
    Posts
    415
    Ross,

    It is difficult to say for sure without seeing the model or the run report, but in general, a VFD with PRessure based simple controls definitely can be an unstable creation.

    Since you have simple controls based on a remote pressure for J-684 and potentially have a VSP pressure on discharge pressure it is difficult to say why the pump remains off without seeing what is happening at J-684 and verifying the VSP control setup.

    The other potential oddity is your On rule says on if above 155 and and off if below 145 at J-684. This seems a bit unusual in that it is usually on for low pressure and off for high pressure, but you have it as on for high pressure and off for low pressure for one pump and on for below 155 and off for below 171 for the other pump.

    With a VSP generally the HGL will remain constant as long as the pumps have enough capacity to handle the flow and so pressure based controls would generally not be applicable as the pressure would be expected to remain essentially constant at the control point and if you use additional parallel pumps will urn on the pumps as needed to maintain the discharge HGL or flow indicated.

    I think your pump 1 control is backward and this causes your issues.

    Can you review that control and then comment back?

    Patrick Moore



    Quote Originally Posted by RossV View Post
    I am troubleshooting why a pump is not remaining off. Three pumps are set to shut off when the level in a tank hits 113'. One of these pumps continues to turn on unexpectedly. This pump also has controls based on downstream pressure and a VFD setting. However, the results graphs don't make sense given these control points. During the shown time, the tank is full, so all pumps should be off, but pump 1 continues to cycle. Any ideas?
    Capture.JPGcontrols.JPG

    Also here is pump 2 and its controls which correctly shuts off:
    pump2.jpgcontrols2.JPG

    Thanks,
    Ross

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