Trane TRG-TRC016-EN manual Single-Chiller System

	period two
	Chilled-Water System Design
notes
	effects. System effects include pump–system curve interaction, dynamic head
	variations, and variation in distribution system flow.
	There are benefits to maintaining a constant water flow rate through the chiller
	evaporator. Constant flow provides more-stable and-simple chiller and system
	operation. However, there is potential for energy savings by varying the water
	flow in the distribution system. Applying these two seemingly-conflicting
	principles to chilled-water systems requires careful planning and a thorough
	understanding of hydraulic system operation.
	Due to advances in technology, however, many of today’s chillers can operate
	with variable evaporator water flow. Chilled-water systems that are specifically
	designed to vary evaporator water flow are discussed in Period Three. This
	period focuses on systems that employ constant water flow through the chiller
	and either constant or variable water flow through the rest of the distribution
	system.
	Single-Chiller System
		air-cooled
		chiller
		pump	coil

three-wayvalve Figure 39

Another factor that influences chilled-water system design is the number of chillers used. Single chillers are sometimes used in small systems (less than 100 tons [35 kW]), while larger or critical systems typically use multiple chillers.

Many single-chiller systems resemble the one shown in Figure 39. This system uses a single pump to move water through the chiller and load terminals. The load terminals are controlled using three-way modulating valves. The pump delivers a constant flow of water throughout the entire system, and flow balance is relatively easy.

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