Type of Chiller Sequencing (CPO) - Johnson Controls - Metasys - LIT-12011147 - Software Application - Controller Configuration Tool - 15.0

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Johnson Controls
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Controller Configuration Tool
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User Guide
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Chiller sequencing methods may involve Building Load, or other methods, such as Chiller Load (chiller only), Flow Differential, and Temperature Differential. Building Load produces the most accurate measurement of the building load by monitoring a building BTU meter or calculating the building load from temperature and flow inputs, then selects chillers to meet the load.

Building Load

The building cooling load is provided by a BTU Meter Analog Input or is calculated inside the Load Calculator module (a Setpoint/Miscellaneous module), using the chilled water temperature difference and the primary chilled water flow input. The Percent Load is the percentage of the current building load to the total chiller plant available.

Chiller Load

Chiller Load method calculates each chiller's current operating capacity based on either its Percent Full Load Amps or Actual Amps and the defined chiller capacity and then adds all devices to determine the current chiller plant capacity. The Chiller Load sequencing is used on systems that contain only chillers and no heat exchangers.

Decouple Loop Flow (Flow Differential)

The goal of the Flow Differential is to reduce the difference between the secondary chilled water supply flow and the primary chilled water supply flow. When the two flows are equal, the chiller plant just meets the building cooling load demand and operates most efficiently. The Flow Differential method is used only with the primary/secondary chilled water pumping configuration.

Temperature Differential

Temperature Differential measures the difference between the chilled water supply and return temperatures, and compares this value to the rated temperature drop of the chillers. The Temperature Differential method may be used only on primary constant speed pumps.