The Building Load method, and specifically the use of a specialized Building Load device (such as a BTU meter AI) produces the most accurate measurement of the chiller plant load.
The Load Calculation module applies the appropriate correction factors for the fluid media for Pure Water, Water-Ethylene Glycol Solution, or Water-Propylene Glycol solutions. To specify which type of fluid media, edit the details of the Load Calculation Media attribute.
When using the Building Load method, it is possible that the building load is not met because the operating chillers cannot deliver their rated capacity. Reasons for this situation could be a fouled chiller or a day that is beyond the Building’s cooling design day. The chiller may only be able to reach a 78% load, but is configured to reach 85% to add another chiller. Therefore, the default application provides logic which forcing an upstage to occur under the following conditions:
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The CHW Supply Temperature is greater than the CHW Supply Temperature Setpoint for more than a given period of time (default = 20 minutes).
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The CHW Supply Flow is greater than the CHW Max Flow for more than a given period of time (default = 20 minutes). The CHW Max Flow is the sum of the rated CHW Max Flows of requested chillers which are defined by the user when configuring the Chiller Selector.