Trane TRG-TRC016-EN manual Chiller

period three

System Variations

notes

Swing Chiller

	100
				swing chiller
load	80
		swing chiller
cooling	60			chiller 2
percent
	40
	20
swing chiller				chiller 1
	0
			chiller sequence		Figure 82

The smaller swing chiller is turned on to handle the low cooling loads either during the night or during unoccupied periods of time. When the building load exceeds the capacity of the swing chiller, it is turned off and a larger chiller is turned on. The larger chiller handles the building cooling load alone until it becomes fully loaded. Then the swing chiller is turned on again. The swing chiller is alternated on and off between the larger chillers' operation to serve as a smaller incremental step of loading. This sequence more favorably matches the capacity of the chiller plant to the system load. It keeps the large chillers loaded in their peak efficiency range and operates with the fewest, and smallest, pieces of ancillary equipment (pumps and cooling towers) at any system load.

A common concern is to prevent the swing chiller from cycling too frequently, which could shorten the life of the equipment. In large chilled-water systems, however, the changes in building load typically occur slowly enough that this is not a problem.

A final asymmetric design option is to use one high-efficiency chiller and one or more standard-efficiency chillers. In this type of system, the high-efficiency chiller should be preferentially loaded to minimize system energy consumption.

74 TRG-TRC016-EN