Carrier 19XRV Start-up, Operation And Maintenance Instructions Manual

Also see for AquaEdge 19XRV series: Start-up, operation and maintenance instructions Start-up and service instructions Installation instructions Start-up, operation and maintenance instructions Start-up and service instructions

Contents

335 - PIC III SYSTEM FUNCTIONSNOTE: Words not part of paragraph headings and printedin all capital letters can be viewed on the ICVC (e.g.,LoCAL, CCN, RUNNING, ALARM, etc.).Words printed in both all capital letters and italics can alsobe viewed on the ICVC and are parameters (CONTROLMODE, TARGET GUIDE VANE POS, etc.) with associatedvalues (e.g., modes, temperatures, pressures, percentages,on, off, enable, disable, etc.).Words printed in all capital letters and bold representsoftkeys on the ICVC (e.g. enteR and eXIt).See Table 3 for examples of the type of information that canappear on the ICVC screens. Figures 3-9 give an overviewof ICVC operations and menus. The sequence of screensthat should be selected to view any parameter in the ICVCoperations and menus.5.1 - Capacity controlGenerally the chiller adjusts capacity in response to deviationof leaving or entering chilled water temperature fromCONTROL POINT. CONTROL POINT is based on theconfigured SETPOINT (in the SETPOINT screen: LCWSET POINT or ECW SET POINT or ICE BUILD SETPOINT), and CONTROL POINT is equal to this SETPOINTplus any active chilled water reset value. A reset value mayoriginate from any of the three chilled water/brine resetoptions configured in the ICVC Service/Equipment Service/TEMP_CTL screen (see page 4) or from a CCN device.The default reset value is 0 K. CONTROL POINT may beviewed or manually overridden from the MAINSTAT screen.Minor adjustments to the rate of capacity adjustment canbe made by changing PROPORTIONAL INC (Increase)BAND, PROPORTIONAL DEC (Decrease) BAND, andPROPORTIONAL ECW (Entering Chilled Water) GAINin the Service/Equipment Service/SETUP screen. Increas-ing the PROPORTIONAL INC BAND or PROPORTIO-NAL DEC BAND, or decreasing PROPORTIONAL ECWGAIN will reduce the amplitude of the capacity controlresponse (within limits). See also Proportional Bands andGain on page 34.Factors and variables used in the capacity control determina-tion are displayed in the Service/Control Algorithm Status/Capacity screen and in the Status/COMPR screen. Viewingthis data will aid in troubleshooting and understandingcurrent operation.5.1.1 - Variable speed (VFD) applicationThe PIC III controls the machine capacity by modulatingboth motor speed and inlet guide vanes in response to chilledwater temperature deviation from the CONTROL POINT(see above). During operation, when the CONTROL POINTis not met within 1/3 of the width of the CHILLED WATERDEADBAND, the controller will calculate a GUIDEVANE DELTA which will effect a percentage change toeither the guide vane position or TARGET VFD SPEED.Factors considered in the capacity control algorithm include:(1) the sign and magnitude of GUIDE VANE DELTA(based on deviation from CONTROL POINT adjusted forthe error trends and CHILLED WATER DEADBAND),() ACTUAL GUIDE VANE POSITION, (3) ACTUALVFD SPEED, and (4) surge prevention mode. Generallythe controller will maintain the highest inlet guide vanesetting at the lowest speed to maximise efficiency whileavoiding surge.First, the calculation of GUIDE VANE DELTA is performed.If GUIDE VANE DELTA is positive, the response will bean IGV or VFD position increase (within limits). If GUIDEVANE DELTA is negative, the response will be an IGV orVFD position decrease (within limits). Next, the surgeprevention mode is determined based on location of thepresent operating point on the CHILLED WATER DELTAT/ACTIVE DELTA P map relative the configured surgeprevention line. This mode will either be Normal or SurgePrevention. The following table indicates which output ismodulated first. When the first output reaches its limit(ACTUAL GUIDE VANE position reaches maximum),the second output is modulated. See Table 4.Table 4 - Guide vane delta modesGuide vane delta Normal control mode Surge prevention modeIGV VFD IGV VFDFrom +0.2 to+2.0Increase 1st Increasewhen IGV =maxIncrease only ifVFD speed =max and if hotgas bypass ispresent andopenIncrease 1stFrom –0.2 to–2.0Decreasewhen VFDspeed = minDecrease1stDecrease —Normal control mode occurs when ACTIVE DELTA T >SURGE/HGBP DELTA T.Surge prevention mode occurs when ACTIVE DELTA T.SURGE/HGBP DELTA T.The VFD GAIN parameter allows for additional adjustmentof the VFD response. Increasing VFD GAIN will increasethe rate of speed change.Generally for the case of line voltage equaling motorvoltage (400 V), VFD output (motor) current is a few per-cent higher than line current at full speed (50 Hz). As drivespeeds decrease from maximum, drive output voltagedecreases linearly with output frequency, and motor currentcontinues to increase relative to line current.