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

Also see for HERMETIC CENTRIFUGAL LIQUID CHILLERS 19XR: User manual Start-up and service instructions Installation instructions Product data Installation instructions

Contents

Carrier 19XR Start-up, Operation And Maintenance Instructions Manual Manual pdf 32 page image

PIC II System FunctionsNOTE: Words not part of paragraph headings and printedin all capital letters can be viewed on the CVC (e.g., LO-CAL, CCN, RUNNING, ALARM, etc.). Words printed inboth in all capital letters and italics can also be viewed onthe CVC and are parameters (CONTROL MODE, COOL-ING SET POINT, TARGET GUIDE VANE POS, etc.) withassociated values (e.g., modes, temperatures, pressures, per-centages, on, off, enable, disable, etc.). Works printed in allcapital letters and in a box represent softkeys on the CVC(e.g., ENTER and EXIT ). See Table 2 for examples ofthe type of information that can appear on the CVC screens.Figures 12-18 give an overview of CVC operations and menus.CAPACITY CONTROL — The PIC II controls the chillercapacity by modulating the inlet guide vanes in response tochilled water temperature changes away from the CON-TROL POINT. The CONTROL POINT may be changed bya CCN network device or is determined by the PIC II addingany active chilled water reset to the SET POINT. The PIC IIuses the PROPORTIONAL INC (Increase) BAND, PRO-PORTIONAL DEC (Decrease) BAND, and the PROPOR-TIONAL ECW (Entering Chilled Water) GAIN to determinehow fast or slow to respond. CONTROL POINT may be viewedor overridden from the MAINSTAT screen.ECW CONTROL OPTION — If this option is enabled, thePIC II uses the ENTERING CHILLED WATER temperatureto modulate the vanes instead of the LEAVING CHILLEDWATER temperature. The ECW CONTROL OPTION may beviewed on the TEMP_CTL screen, which is accessed fromthe EQUIPMENT SERVICE screen.CONTROL POINT DEADBAND — This is the tolerancerange on the chilled water/brine temperature control point.If the water temperature goes outside the CHILLED WATERDEADBAND, the PIC II opens or closes the guide vanes un-til the temperature is within tolerance. The PIC II may beconfigured with a 0.5 to 2 F (0.3 to 1.1 C) deadband. CHILLEDWATER DEADBAND may be viewed or modified on theSETUP1 screen, which is accessed from the EQUIPMENTSERVICE table.For example, a 1° F (0.6° C) deadband setting controlsthe water temperature within ±0.5° F (0.3° C) of the controlpoint. This may cause frequent guide vane movement if thechilled water load fluctuates frequently. A value of 1° F(0.6° C) is the default setting.DIFFUSER CONTROL — On 19XR compressors equippedwith a variable discharge diffuser, the PIC II adjusts the dif-fuser actuator position (DIFFUSER ACTUATOR on the COM-PRESS screen) to correspond to the actual guide vane po-sition (ACTUAL GUIDE VANE POS on the COMPRESSscreen).The diffuser control can be enabled or disabled from theSETUP2 screen. See Table 2, Example 18. In addition, thediffuser and guide vane load points may be viewed and modi-fied from this screen. These points must be correct for thecompressor size. The diffuser opening can be incrementedfrom fully open to completely closed. A 0% setting is fullyopen; a 100% setting is completely closed. To obtain the propersettings for Diffuser Control, contact a Carrier Engineeringrepresentative.PROPORTIONAL BANDS AND GAIN — Proportional bandis the rate at which the guide vane position is corrected inproportion to how far the chilled water/brine temperature isfrom the control point. Proportional gain determines howquickly the guide vanes react to how quickly the tempera-ture is moving from the CONTROL POINT. The propor-tional bands and gain may be viewed or modified from theSETUP2 screen, which is accessed from the EQUIPMENTSERVICE table.The Proportional Band — There are two response modes,one for temperature response above the control point, theother for the response below the control point.The temperature response above the control point is calledthe PROPORTIONAL INC BAND, and it can slow or quickenguide vane response to chilled water/brine temperatures abovethe DEADBAND. The PROPORTIONAL INC BAND can beadjusted from a setting of 2 to 10; the default setting is 6.5.The response below the control point is called thePROPORTIONAL DEC BAND, and it can slow or quickenthe guide vane response to chilled water temperature belowthe deadband plus the control point. The PROPORTIONALDEC BAND can be adjusted on the CVC from a setting of2 to 10. The default setting is 6.0.NOTE: Increasing either of these settings causes the guidevanes to respond more slowly than they would at a lowersetting.The PROPORTIONAL ECW GAIN can be adjusted on theCVC display for values of 1, 2, or 3; the default setting is 2.Increase this setting to increase guide vane response to a changein entering chilled water temperature.DEMAND LIMITING — The PIC II responds to theACTIVE DEMAND LIMIT set point by limiting the openingof the guide vanes. It compares the ACTIVE DEMAND LIMITset point to the DEMAND LIMIT SOURCE (either theAVERAGE LINE CURRENT or the MOTOR KW). Depend-ing on how the control is configured. DEMAND LIMITSOURCE is on the RAMP_DEM screen. The default sourceis the compressor motor current.CHILLER TIMERS — The PIC II maintains 2 runtime clocks,known as COMPRESSOR ONTIME and SERVICE ON-TIME. COMPRESSOR ONTIME indicates the total life-time compressor run hours. This timer can register up to500,000 hours before the clock turns back to zero. TheSERVICE ONTIME is a reset table timer that can be used toindicate the hours since the last service visit or any otherevent. The time can be changed from the CVC to whatevervalue is desired. This timer can register up to 32,767 hoursbefore it rolls over to zero.The chiller also maintains a start-to-start timer and a stop-to-start timer. These timers limit how soon the chiller can bestarted. START INHIBIT TIMER is displayed on theMAINSTAT screen. See the Start-Up/Shutdown/Recycle Se-quence section, page 44, for more information on this topic.OCCUPANCY SCHEDULE — The chiller schedule, de-scribed in the Time Schedule Operation section (page 19),determines when the chiller can run. Each schedule consistsof from 1 to 8 occupied or unoccupied time periods, set bythe operator. The chiller can be started and run during anoccupied time period (when OCCUPIED ? is set to YES onthe MAINSTAT display screen). It cannot be started or runduring an unoccupied time period (when OCCUPIED ? isset to NO on the MAINSTAT display screen). These timeperiods can be set for each day of the week and for holidays.The day begins with 0000 hours and ends with 2400 hours.The default setting for OCCUPIED ? is YES, unless an un-occupied time period is in effect.These schedules can be set up to follow a building’s oc-cupancy schedule, or the chiller can be set so to run 100%of the time, if the operator wishes. The schedules also can bebypassed by forcing the CHILLER START/STOP parameteron the MAINSTAT screen to START. For more informationon forced starts, see Local Start-Up, page 44.The schedules also can be overridden to keep the chillerin an occupied state for up to 4 hours, on a one time basis.See the Time Schedule Operation section, page 19.32