Carrier AquaEdge 19XRV series Operation, Maintenance And Installation 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

50To determine what caused the alarm, the operator should readboth the primary and secondary default screen messages, as wellas the alarm history. The primary message indicates the mostrecent alarm condition. The secondary message gives moredetail on the alarm condition. Since there may be more than onealarm condition, another alarm message may appear after thefirst condition is cleared. Check the ALARM HISTORY screenfor additional help in determining the reasons for the alarms.Once all existing alarms are cleared (by pressing thesoftkey), the default ICVC display returns to normal operation.Ramp Loading — The ramp loading control slows downthe rate at which the compressor loads up. This control can pre-vent the compressor from loading up during the short period oftime when the chiller is started and the chilled water loop has tobe brought down to CONTROL POINT. This helps reduceelectrical demand charges by slowly bringing the chilled waterto CONTROL POINT. The total power draw during this periodremains almost unchanged.There are several methods of ramp loading with the PIC III.Ramp loading can be based on LEAVING CHILLED WATER,ENTERING CHILLED WATER, PERCENT LINE CURENT,or PERCENT MOTOR KILOWATTS. PULLDOWN RAMPTYPE is selected from the RAMP__DEM screen.1. Temperature ramp loading (TEMP PULLDOWN DEG/MIN) limits the degrees per minute rate at which eitherLEAVING CHILLED WATER or ENTERING CHILLEDWATER temperature decreases. This rate is configured bythe operator on the TEMP_CTL screen.NOTE: If chiller control power has been off for 3 hours ormore, the next start-up (only) will follow temperature ramploading using the minimum rate regardless of the ramp loadingmethod and rate which are configured in the screens. This isused to maximize oil reclaim during start-up.2. Motor load ramp loading (AMPS OR KW RAMP %/MIN) limits the rate at which the compressor motor cur-rent or compressor motor load increases. The AMPS ORKW RAMP %/MIN rate is configured by the operatoron the RAMP_DEM screen in line current or motorkilowatts.If kilowatts is selected for the DEMAND LIMIT SOURCE,the MOTOR RATED LOAD KILOWATTS must be entered inthe VFD_CONF screen.The TEMP PULLDOWN DEG/MIN may be viewed ormodified on the TEMP_CTL screen which is accessed fromthe EQUIPMENT SERVICE screen. PULLDOWN RAMPTYPE, DEMAND LIMIT SOURCE, and AMPS OR KW RAMP%/MIN may be viewed or modified on RAMP_DEM screen.Rampdown — The Rampdown control applies to VFDequipped chillers. At machine start-up the VFD speed is set to“Start Speed” which is the lower of VFD MAXIMUM SPEEDor the configured value of VFD START SPEED. VFD STARTSPEED is configured on the SETUP2 screen. After RampLoading is complete the control begins to reduce the VFDspeed. Speed reduction continues until the leaving water tem-perature is within the control point deadband and any conditionis reached that would require the VFD speed to hold or in-crease. The chiller is then out of Rampdown and running innormal capacity control.Capacity Override — Capacity overrides can preventsome safety shutdowns caused by exceeding the motor amper-age limit, low evaporator temperature safety limit, high motortemperature safety limit, and high condenser pressure limit. Inall cases, there are two stages of compressor capacity controlapplied by guide vane operation:1. When the value of interest crosses the First Stage SetPoint into the Override Region, the guide vanes areprevented from opening further, and the status line on theICVC indicates the reason for the override. Normalcapacity control operation is restored when the valuecrosses back over the First Stage Set point, leaving theOverride Region. See Table 7.2. When the value of interest is in the Override Region andfurther crosses the Second Stage Set Point, the guidevanes are closed until the value meets the OverrideTermination Condition. The PIC III controls resumenormal capacity control operation after the overridetermination condition has been satisfied. (In the case ofhigh discharge superheat, there is an intermediate stage.)Whenever the motor current demand limit set point(ACTIVE DEMAND LIMIT) is reached, it activates a capacityoverride, again, with a 2-step process. Exceeding 110% of therated load amps for more than 30 seconds will initiate a safetyshutdown.The high compressor lift (surge prevention) set point willcause a capacity override as well. When the surge preventionset point is reached, the controller normally will only preventthe guide vanes from opening. If so equipped, the hot gasbypass valve will open instead of holding the vanes. The hotgas bypass will only open if the compressor is at 100% speed.See the Surge Prevention Algorithm section, page 54.High Discharge Temperature Control — If theCOMP DISCHARGE TEMP increases above 160 F (71.1 C),the guide vanes are proportionally opened to increase gas flowthrough the compressor. If the LEAVING CHILLED WATERtemperature decreases 5 F (2.8 C) below the control set pointtemperature, as a result of opening the guide vanes, the PIC IIIwill bring the chiller into the recycle mode.Compressor Bearing Temperature — The thrustbearing temperature (MTRB) is a calculated value which is thetemperature of the oil leaving the bearing plus an internal incre-ment calculated with the THRUST BRG RESET FACTOR. TheComp Thrust Bearing Reset is calculated using the rate ofchange of the oil leaving the bearing. If the oil temperature isstable the COMP THRUST BRG TEMP equals the COMPTHRUST LVG OIL TEMP. As the oil temperature rises, theCOMP THRUST BRG RESET is calculated to account for anylag between actual bearing temperature and the temperature ofthe leaving oil.In the SETUP1 screen an adjustment called the THRUSTBRG RESET FACTOR is an adjustment to the COMP THRUSTBRG TEMP calculation. The default value is 1.4 and will nor-mally be left at that value unless other wise advised by CarrierService Engineering.Oil Sump Temperature and Pump Con-trol — The oil sump temperature is regulated by the PIC III,with the oil heater relay when the chiller is shut down.As part of the pre-start checks executed by the controls, theoil sump temperature (OIL SUMP TEMP) is compared tothe cooler refrigerant temperature (EVAPORATOR REFRIGTEMP) if the OIL SUMP TEMP is less than 150 F (65.6). If thedifference between these 2 temperatures is 50 F (27.8 C) orless, the start-up will be delayed until either of these conditionsis no longer true. Once this temperature criteria is satisfied, thestart-up continues.The oil heater relay is energized whenever the chiller com-pressor is off and the oil sump temperature is less than 140 F(60.0 C) or the OIL SUMP TEMP is less than the EVAPREFRIG TEMP plus 53 F (29.4 C). The oil heater is turned offwhen the OIL SUMP TEMP is either:• more than 152 F (66.7 C), or• more than 142 F (61.1 C) and more than the EVAP REFRIGTEMP plus 55 F (30.6 C).The oil heater is always off during start-up or when thecompressor is running.RESET