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Sequantial load scheme isn't working

asked 2018-04-30 10:51:40 -0600

lyw0211 gravatar image

updated 2018-05-01 07:02:01 -0600

Hi, I'm using the E+ 8.7 and I have a trouble of letting the chiller outlet node temperature meet the same setpoint as the chilled water system when I was using the sequantial load as the load distribution scheme. The current logic E+ used is that the average of the CHW supply temperature from different chillers will meet the CHW supply temperature setpoint instead of making each chiller's CHW supply temperature do it.

My model has 3 chillers totally. ch-1 and ch-2 are working at daytime on weekdays and ch-3 is working at the rest of the time. (So we can focus on the CHW supply temperature of ch-1 and ch-2.)

I added the SetpointManager to each of the chiller's outlet node. For the object of Chiller:Electric:EIR, I also set up the min supply CHW temp the same as the stepoint and changed the chiller flow mode to LeavingSetpointModulated.

However, the sequantial load didn't work after the chiller's outlet node temperature meet the setpoint. In fact, the scheme looks like the uniform load.

In order to make the SequantialLoad scheme work again, I used the PlantEquipmentOperationSchemes object based on the answers from the similar question here. So the different cooling load range can have the different equipment list.

Finally, the result is pretty weird: when the SequantialLoad scheme works, the ch-1 and ch-2 have the different supply CHW temperature; when the ch-1 and ch-2 have the same supply CHW temperature, the SequantialLoad scheme didn't work (it becomes uniform load again). Now I have no idea about how to make both SequantialLoad scheme and the same chiller supply temperature work together.

Anyone had the same experience before? Any ideas about how to fix this issue? Thanks!

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answered 2018-04-30 11:07:42 -0600

You can try the option "SequentialUniformPLR", this option was added to ensure that when chillers are sequentially loaded, once a chiller comes online, the chillers would have the same part load ratio, so that they would generate chilled water at the same temperature.

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@TiejunWu, Hi, thanks for your answer. In reality, the ch-1 starts to work until it meets its 100%PLR, and then the ch-2 starts to work to take the rest of the cooling load. So the scheme you mentioned didn't work on my case.

lyw0211 gravatar image lyw0211  ( 2018-04-30 12:27:26 -0600 )edit

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Asked: 2018-04-30 10:51:40 -0600

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Last updated: Apr 30 '18