Trane TRG-TRC004-EN manual Compressor Capacity Control, 0HWKRGVRI&RPSUHVVRU8QORDGLQJ

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Compressor Capacity Control

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Figure 27

The capacity of a compressor is defined by the volume of evaporated refrigerant that can be compressed within a given time period. The compressor needs a method of capacity control in order to match the ever-changing load on the system.

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Figure 28

Capacity control is commonly accomplished by unloading the compressor. The method used for unloading generally depends on the type of compressor.

Many reciprocating compressors use cylinder unloaders. Scroll compressors generally cycle on and off. Helical-rotary compressors use a slide valve or a similar unloading device. Centrifugal compressors typically use inlet vanes or a variable-speed drive in combination with inlet vanes. In addition, all four types of compressors could use variable speed to control their capacity.

18 TRG-TRC004-EN