A method to determine the 'best' differential pressure sensor location for pump speed control in a variable-volume-flow chilled water distribution system has been presented by Lau. In this Note, Lau's method is reviewed and alternative expressions for determining the sensor location and pumping requirement are derived, which include the effects of water pressure drop across the chilled water coils. Neglecting this will lead to overestimation of the improvement on the valve authority and the reduction in pumping pressure. Issues related to this method of control, including pump energy saving and water balancing are discussed
Get full access to this article
View all access options for this article.
References
1.
Lau K.K.Variable-volume-flow secondary water systems: Best location for differential pressure sensing and controlBuilding Serv. Eng. Res. TechnoL15(1) 25-26 (1994)
2.
Automatic controls Applications Manual AM1 (London: Chartered Institution of Building Services Engineers) ( 1985)
3.
Water distribution systems Commissioning Code W (London : Chartered Institution of Building Services Engineers (1989)
4.
Hansen E.G.Hydronic system design and operation: A guide to hearing and cooling with water pp288-289 (New York: McGraw-Hill ) (1985)
5.
Avery G.Balancing a variable flow water system will ruin the control system in The pros and cons of balancing a variable flow water systemASHRAE J.32(10) 30-34 (October 1990)
