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

46the control’s model of the surge prevention line up. Guidevanes are not permitted to open further when surge preventionis on. Once speed has been increased to maximum, if still oper-ating in the surge prevention region, and if the Hot Gas Bypassoption is installed, the hot gas bypass valve will open. When inSurge Prevention mode, with a command to decrease capacitythe guide vanes will close but speed will not decrease.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 caneventually cause chiller damage. When enabled, the SurgePrevention Algorithm will adjust either the ACTUAL GUIDEVANE POSITION or ACTUAL VFD SPEED to maintain thecompressor at a safe distance from surge while maintainingmachine efficiency. If the surge condition degrades then thealgorithm will move aggressively away from surge. Thiscondition can be identified when the SURGE/HGBP ACTIVE?on the HEAT_EX display screen displays a YES.The surge prevention algorithm first determines if correc-tive action is necessary. The algorithm checks two sets ofoperator-configured data points, the lower surge point (MIN.LOAD POINT [T1,P1]) and the upper surge point (FULLLOAD POINT [T2,P2]). The surge characteristics varybetween different chiller configurations and operatingconditions.The surge prevention algorithm function and settings aregraphically displayed on Fig. 22 and 23. The two sets of loadpoints on the graph (default settings are shown) describe aline the algorithm uses to determine the maximum lift ofthe compressor for the design maximum operating speed.When the actual differential pressure between the cooler andcondenser (delta P) and the temperature difference between theentering and leaving chilled water (delta T) are above the lineon the graph (as defined by the MIN LOAD POINTS and FULLLOAD POINTS), the algorithm operates in Surge Preventionmode. This is determined when the ACTIVE DELTA T is lessthan SURGE/HGBP DELTA T minus the SURGE/HGBPDEADBAND.When in Surge Prevention mode, with a command toincrease capacity, the VFD speed will increase until VFDMAXIMUM SPEED is reached. At VFD MAXIMUM SPEED,when Capacity still needs to increase, the inlet guide vanes(IGV) open. When in Surge Prevention mode, with a commandto decrease capacity, the IGVs will close. The optional hot gasbypass will open in surge prevention mode only if the TARGETVFD SPEED is at the VFD MAXIMUM SPEED.Surge Protection — The PIC III monitors surge, whichis detected as a fluctuation in compressor motor amperage.Each time the fluctuation exceeds an operator-specified limit,the PIC III registers a surge protection count. The currentfluctuation threshold that triggers a surge protection count isequal to the sum of SURGE DELTA % AMPS plus theCHILLED WATER DELTA T. If more than 5 surges occurwithin an operator-specified time (SURGE TIME PERIOD),the PIC III initiates a surge protection shutdown of the chiller.The SURGE PROTECTION COUNTS remain displayed in theCOMPRESS screen until the alarm is reset, at which time theyare re-zeroed.If a surge count is registered and if ACTUAL VFD SPEEDis less than VFD MAXIMUM SPEED then motor speed will beincreased by the configured VFD INCREASE STEP. Whilethe SURGE PROTECTION COUNTS are > 0, a speed decreasewill not be honored.The portion of the surge count threshold attributable to cur-rent can be adjusted from the OPTIONS screen (see Table 4).Scroll down to the SURGE DELTA % AMPS parameter, anduse the or softkey to adjust thepercent current fluctuation. The default setting is 10% amps.The SURGE TIME PERIOD can also be adjusted from theOPTIONS screen. Scroll to the SURGE TIME PERIODparameter, and use the or softkeyto adjust the amount of time. The default setting is 8 minutes.Access the display screen (COMPRESS) to monitor thesurge count (SURGE PROTECTION COUNTS).INCREASE DECREASEINCREASE DECREASELEGENDΔP = (Condenser psi) – (Cooler psi)ΔT = (ECW) – (LCW)Fig. 22 — 19XRV Hot Gas Bypass/SurgePrevention with Default English SettingsECW — Entering Chilled WaterHGBP — Hot Gas BypassLCW — Leaving Chilled WaterLEGENDΔP = (Condenser kPa) – (Cooler kPa)ΔT = (ECW) – (LCW)Fig. 23 — 19XRV Hot Gas Bypass/SurgePrevention with Default Metric SettingsECW — Entering Chilled WaterHGBP — Hot Gas BypassLCW — Leaving Chilled Watera19-1621a19-1622