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

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Compressor Capacity Control

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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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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

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Contents Air Conditioning Clinic Refrigeration Compressors Business Reply Mail One of the Fundamental Series Comment CardRefrigeration Compressors 5HIULJHUDWLRQ&RPSUHVVRUV PrefaceContents TRG-TRC004-EN 9DSRU&RPSUHVVLRQ5HIULJHUDWLRQ Introduction5HIULJHUDWLRQ&\FOH RPSUHVVRU7\SHV Compressor TypesReciprocating Compressor 5HFLSURFDWLQJ&RPSUHVVRUFrpsuhvvlrq Vwurnh Rshqlqj Glvfkdujh Slvwrq Scroll Compressor 6FUROO&RPSUHVVRUMrxuqdo Lqwdnh Skdvh Frpsuhvvlrq Glvfkdujh Helical-Rotary Screw Compressor +HOLFDO5RWDU\6FUHZ&RPSUHVVRU+HOLFDO5RWDU\&RPSUHVVRU Phvklqjsrlqw Centrifugal Compressor HQWULIXJDO&RPSUHVVRUYroxwh Gliixvhu Sdvvdjhv Udgldo Lpshoohu Eodghv Uhiuljhudqw 2SHQ&RPSUHVVRU 6HPLKHUPHWLF&RPSUHVVRU +HUPHWLF&RPSUHVVRU0HWKRGVRI&RPSUHVVRU8QORDGLQJ Compressor Capacity ControlCylinder Unloaders \OLQGHU8QORDGHUVXqordghufrqwuroohu Vrohqrlgydoyh Ydoyh DSDFLW\9HUVXV6XFWLRQ7HPSHUDWXUH RPSUHVVRU8QORDGLQJ $OWHUQDWLQJ&\OLQGHUV2QDQG2II \FOLQJ6FUROO&RPSUHVVRUV \FOLQJ2QDQG2IICycling On and Off \FOLQJ6FUROO&RPSUHVVRUV Slide Valve 6OLGH9DOYHInlet Vanes QOHW9DQHVInlet vanes presented in this section of the clinic Variable Speed 9DULDEOH6SHHG\VWHP/HYHO&RQWURO Compressor in a SystemSystem-Level Control RQVWDQW9ROXPH6\VWHP KLOOHGDWHU6\VWHP 9DULDEOH$LU9ROXPH6\VWHPPreventing Evaporator Freeze-Up 6HQVLQJ6XFWLRQ7HPSHUDWXUH +RW*DV%\SDVVWRYDSRUDWRU,QOHW +RW*DV%\SDVVWR6XFWLRQ/LQH System Components clinic 5HYLHZ²3HULRG2QH Review5HYLHZ²3HULRG7ZR \VWHPOHYHOFRQWURO 5HYLHZ²3HULRG7KUHHFor more information, refer to the following references TRG-TRC004-EN Questions for Period QuizAnswers Glossary Glossary Glossary Trane Company