.Buildings.DHC.Plants.Cooling.Controls.ChillerStage

Information

This model implements the staging control logic as follows:

• When the plant enabling signal on changes from false to true, one chiller is enabled.
• When the total cooling load QLoa exceeds 80 percent (adjustable) of one chiller's nominal capacity QChi_nominal, a second chiller is enabled.
• When the total cooling load QLoa drops below 60 percent (adjustable) of one chiller's nominal capacity QChi_nominal (i.e. 30 percent of both chillers combined), or the plant enabling signal on changes from true to false, the second chiller is disabled.
• When the plant enabling signal on changes from true to false, the operating chillers will be disabled sequentially.
• Parameter tWai assures a transitional time is kept between each operation.

It is assumed that both chillers have the same capacity of QChi_nominal.

Note: This model can be used for plants with two chillers with or without waterside econimizer (WSE). For plants with WSE, extra control logic on top of this model needs to be added.

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Contents

Name	Description
Medium	Service side medium

Revisions

• December 10, 2021, by Michael Wetter:
  Corrected parameter value for twoOn.nOut. This correction is required to simulate the model in Dymola 2022 if the model has been updated to MSL 4.0.0. With MSL 3.2.3, the simulation works without this correction.
  This is for Buildings, #1563.
• August 6, 2020 by Jing Wang:
  First implementation.