System controls for pumps and circulators

Control sequences are a key element in achieving energy management and savings goals. Most water systems’ control sequences are straightforward and easy to use, but the control schemes for the system will vary with the size and complexity of the system, and especially with the type of pumping scheme chosen. Most chilled water (CHW) systems’ flow rates can be controlled from differential pressure. This control option provides some reliability but at times may have limited flexibility for operational changes, and can waste energy in overpumping. In the past, this differential pressure has been measured at the chilled water plant, in the piping distribution system, and/or at the hydraulically most remote location. ASHRAE Standard 90.1 indicates it should be measured at or near the most remote heat exchanger or the heat exchanger requiring the greatest differential pressure. 

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