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

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

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Carrier AquaEdge 19XR series Start-up, Operation And Maintenance Instructions Manual Manual pdf 58 page image

58point has moved. This is used to determine the size of the speedboost to the VFD.NOTE: If upon ramp-up, a chiller with VFD tends to go to fullspeed before guide vanes open fully, it is an indication that thelift at low load is excessive, and the operating point moveddirectly into the surge prevention region. In this case, investi-gate the ability of the condenser cooling means (e.g., coolingtower) to provide cooling water in accordance with the designload/entering condenser water temperature schedule.A surge condition occurs when the lift becomes so high thegas flow across the impeller reverses. This condition can even-tually cause chiller damage. When enabled, the Surge Preven-tion Algorithm will adjust either the inlet guide vane (IGV)position or compressor speed to maintain the compressor at asafe distance from surge while maintaining machine efficiency.If the surge condition degrades then the algorithm will moveaggressively away from surge. This condition can be identifiedwhen the SURGE/HGBP ACTIVE? on the HEAT_EX displayscreen displays a YES.When in Surge Prevention mode, with a command to in-crease capacity, the VFD speed will increase until maximumVFD speed is reached. At VFD MAXIMUM SPEED, when Ca-pacity still needs to increase, the IGV’s open. When in SurgePrevention mode and with a command to decrease capacityonly the IGVs will close, the VFD speed will not decrease.Surge Protection (VFD Chiller) — The PIC II mon-itors surge, which results in a fluctuation on the compressormotor amperage. Each time the fluctuation in amperage ex-ceeds an operator-specified limit (SURGE DELTA % AMPS)plus a load correction factor, both SURGE COUNTS are incre-mented by one and the VFD will increase in speed providedthat it is not already operating at VFD MAXIMUM SPEED orthat the VFD TARGET SPEED is forced. If the VFD cannotincrease in speed because the VFD is already at maximumspeed of the target speed is forced then the SURGE PROTEC-TION COUNTS are also incremented by one. If more than 4SURGE PROTECTION COUNTS occur within an operator-specified time (SURGE TIME PERIOD) and the ACTUALVFD SPEED is greater than 90% then the PIC II declares anExcessive Compressor Surge Alarm (238) and the chiller isshut down. If more than four SURGE PROTECTIONCOUNTS occur within the SURGE TIME PERIOD and theACTUAL VFD SPEED is less than 90% then the chiller is shutdown on a Excessive Compressor Surge / Low Speed Alarm(236). Both SURGE COUNTS and SURGE PROTECTIONCOUNTS are decreased by one if no surges occur within theSURGE TIME PERIOD.On chillers with VFDs, if a SURGE COUNT is registeredand the ACTUAL VFD SPEED is less than the VFD MAXI-MUM SPEED then the TARGET VFD SPEED will be in-creased by the amount configured in the VFD INCREASESTEP parameter. The VFD will not decrease in speed ifSURGE COUNTS is greater than zero.The threshold at which a current fluctuation is interpreted asa surge can be adjusted from the OPTIONS screen. The por-tion of the surge threshold attributable to current fluctuationscan be changed by scrolling to the SURGE DELTA % AMPSparameter and adjusting it with the INCREASE or DE-CREASE softkeys. The default setting is 10 %. The SURGETIME PERIOD can be adjusted from the OPTIONS screen.Scroll to the SURGE TIME PERIOD parameter and use theINCREASE or DECREASE softkey to adjust the surge counttime interval. The default setting is 8 minutes.SURGE PROTECTION COUNTS are displayed in theCOMPRESS screen. Both SURGE PROTECTION COUNTSand SURGE COUNTS are displayed in the SURGPREVscreen.VFD Start-Up Speed Control — Immediately accel-erating to a high VFD speed improves the ability of the com-pressor to compensate for some start-up environments that ex-ceed condenser water design conditions. The 19XRV chillersinitially accelerate to high VFD speed and then gradually slowthe compressor, if possible, while adjusting the guide vane po-sition until a stable operating point with improved chiller effi-ciency is attained.Following a start command, the PIC II controls internallyset the VFD TARGET SPEED to the smaller of the VFDMAXIMUM SPEED or the VFD START SPEED. Providedthat the chiller has sufficient capacity, the VFD will continue torun at the startup speed during Ramp Loading until the chilledwater temperature falls within the CHILLED WATER DEAD-BAND surrounding the Setpoint. RAMP LOADING AC-TIVE in the SURGPREV screen will indicate YES duringRamp Loading. The GUIDE VANE DELTA will be equal tozero when the chilled water temperature is in the CHILLEDWATER DEADBAND. The VFD speed will then be rampeddown at one half of the VFD GAIN rate until, surge conditionsare encountered, the VFD MINIMUM SPEED is reached, theACTUAL GUIDE VANE POS reaches the GUIDE VANETRAVEL LIMIT, or the TARGET VFD SPEED is forced.VFD RAMPDOWN ACTIVE in the SURGPREV screen willindicate YES during the rampdown process. The VFD speedwill be regulated by standard capacity control and surge pre-vention algorithms at the conclusion of the rampdown process.Head Pressure Reference Output (SeeFig. 28) — The PIC II control outputs a 4 to 20 mA signalfor the configurable Delta P (CONDENSER PRESSURE mi-nus EVAPORATOR PRESSURE) reference curve shown inFig. 28. An output is available on the ISM module [TerminalJ8-3 (+), J8-4 (–) labeled spare]. The DELTA P AT 100%(chiller at maximum load condition default at 50 psi[344 kPa]), DELTA P AT 0% (chiller at minimum load condi-tion default at 25 psi [172.4 kPa]) and MINIMUM OUTPUTpoints are configurable in the EQUIPMENT SERVICE-OP-TIONS table. When configuring this output ensure that mini-mum requirements for oil pressure and proper condenserFLASC orifice performance are maintained.The output may be useful as a reference signal to control atower bypass valve, tower speed control, condenser pumpspeed control, etc. Note that it is up to the site design engineer-ing agent to integrate this analog output with any external sys-tem device(s) to produce the desired effect. Carrier does notmake any claim that this output is directly usable to control anyspecific piece of equipment (that is, without further control ele-ments or signal conditioning), although it may be.MINIMUMREFERENCEOUTPUTDELTA PAT 100%DELTA PAT 0%DELTA P0 mA 2 mA 4 mA(0%) 20 mA(100%)4 T0 20 mA OUTPUTFig. 28 — Head Pressure Reference Output(Minimum Set Above 4 mA)