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 55 page image

55Condenser Freeze Prevention — This control algo-rithm helps prevent condenser tube freeze-up by energizing thecondenser pump relay. The PIC II controls the pump and, bystarting it, helps to prevent the water in the condenser fromfreezing. The PIC II can perform this function whenever thechiller is not running except when it is either actively in pump-down or in pumpdown/lockout with the freeze preventiondisabled.When the chiller is off and CONDENSER REFRIG TEMPis less than the CONDENSER FREEZE POINT, the CON-DENSER WATER PUMP will be energized (Alert State 154,Potential Freeze Up) However, if the chiller is in pump down,and when it entered pump down mode, the CONDENSINGREFRIG TEMP was more than 5° F (2.7° C) above the CON-DENSER FREEZE POINT, the same low temperature condi-tion will generate Alarm State 244 (Potential Freeze Up) andthe CONDENSER WATER PUMP will be energized. In eithercase, the fault state will clear and the pump will turn off whenthe CONDENSER REFRIG TEMP is more than 5° F (2.7° C)above the CONDENSER FREEZE POINT and the enteringcondenser water temperature is greater than the CONDENSERFREEZE POINT. If the chiller is in Recycle Shutdown Modewhen the condition occurs, the controls will transition to a non-recycle shutdown.Evaporator Freeze Protection — When the EVAP-ORATOR REFRIG TEMP is less than the EVAP REFRIGTRIPPOINT plus the REFRIG OVERRIDE DELTA T (configu-rable from 2° to 5° F or 1.1° to 2.8° C), Alert State 122 will bedisplayed, and a capacity override will occur. (See Table 7.)When the unit is running or in recycle, if the EVAPORATORREFRIG TEMP is equal to or less than the EVAP REFRIGTRIPPOINT (33° F or 0.6° C for water, configurable for brine),Protective Limit Alarm State 232 will be displayed, the unitwill shut down, and the CHILLED WATER PUMP will remainon. The alarm will be clearable when the leaving chilled watertemperature rises 5° F (2.8° C) above the CONTROL POINT.When the unit is off, if the EVAPORATOR REFRIG TEMPis less than the EVAP REFRIG TRIPPOINT plus 1° F (0.6° C),Alarm State 243 will be generated and the CHILLED WATERPUMP will be turned on. The alarm can be reset when theEVAPORATOR REFRIG TEMP rises 5° F (2.8° C) above theEVAP REFRIG TRIPPOINT.Tower Fan Relay Low and High — Low condenserwater temperature can cause the chiller to shut down when re-frigerant temperature is low. The tower fan relays, located inthe starter, are controlled by the PIC II to energize and deener-gize as the pressure differential between cooler and condenservessels changes. This prevents low condenser water tempera-ture and maximizes chiller efficiency. The tower fan relay canonly accomplish this if the relay has been added to the coolingtower temperature controller.TOWER FAN RELAY LOW is turned on whenever the con-denser water pump is running, and the difference betweenEVAPORATOR PRESSURE and CONDENSER PRESSURE ismore than 30 psid (207 kPad) for ENTERING CONDENSERWATER TEMPERATURE greater than 65 F (18.3 C).TOWER FAN RELAY LOW is turned off when the condens-er pump is off or the EVAP REFRIGERANT TEMP is less thanthe EVAP SAT OVERRIDE TEMP for ENTERING CON-DENSER WATER TEMPERATURE less than 62 F (16.7 C), orthe difference between the CONDENSER PRESSURE andEVAPORATOR PRESSURE is less than 25 psid (172.4 kPad)and ENTERING CONDENSER WATER TEMPERATURE isless than 80 F (27 C).TOWER FAN RELAY HIGH is turned on whenever the con-denser water pump is running and the difference betweenEVAPORATOR PRESSURE and CONDENSER PRESSURE ismore than 30 psid (206.8 kPad) and ENTERING CONDWATER temperature is greater than the TOWER FAN HIGHSETPOINT (SETPOINT menu, default 75 F [23.9 C]).The TOWER FAN RELAY HIGH is turned off when theCONDENSER WATER PUMP is off or the EVAPORATORREFRIG TEMP is less than the EVAP REF OVERRIDE TEMPand ENTERING CONDENSER WATER is less than 70 F(21.1 C), or the difference between EVAPORATOR PRES-SURE and CONDENSER PRESSURE is less than 28 Psid(193 kPa), and ENTERING CONDENSER WATER tempera-ture is less than TOWER FAN HIGH SETPOINT minus 3 F(5.4 C).Auto. Restart After Power Failure — ICVCSoftware Version 14 — The Auto Restart feature is en-abled/disabled in the OPTIONS screen.NOTE: This section assumes that a chiller without Uninter-ruptible Power supply has been installed.The following faults will reset when Auto Restart is en-abled: single cycle dropout (if enabled), line current imbalance,high line voltage, low line voltage, and ISM power-on reset(Alerts 143-148). With this feature enabled, these faults aretreated as alerts instead of alarms, so start-up proceeds as soonas the condition has been rectified. The 15-minute start-to-startand 1-minute start-inhibit timers are ignored during this type ofstart-up, and the STARTS IN 12 HOURS counter is not incre-mented.This feature allows the controls to make an express restartas long as the controls have been without power for 20 minutesor less. If the power is off for less than 20 minutes, the timingof the restart is now in an express mode. When enabled, at thetime of power up, if the chiller had been operating at the timeof shutdown, the controls will immediately energize theCHILLED WATER PUMP output, wait 1 second, energize theCONDENSER WATER PUMP output, then wait 1 second tostart to verify water flow. When flow is verified, and thechilled water temperature is calling for cooling, the guide vaneis now checked for closure. If the unit is configured for VFD,then the guide vanes have no closure requirement. If there isno VFD configured, the vanes must be less than or equal to theGUIDE VANE CLOSURE limit set in the OPTIONS table.After guide vanes are checked and in position, the oil pumpis started and when the oil pressure is confirmed the controlswait 4 seconds to maintain pressure. At this point the compres-sor is commanded to start.If the power had been off for longer than 20 minutes, thetiming of the restart will be standard timing for auto restart af-ter power failure. When power is restored (after the longerthan 20-minute power failure) and if the compressor had beenrunning, the oil pump will energize for one minute before ener-gizing the cooler pump. AUTO RESTART will then continuelike a normal start-up. If power to the ICVC module has beenoff for more than 3 hours or the time clock has been set for thefirst time, the compressor starts with the slowest temperature-based ramp load rate possible in order to minimize oil foaming.The oil pump is energized occasionally during the time the oilis being brought up to proper temperature in order to eliminaterefrigerant that has migrated to the oil sump during the powerfailure. The pump turns on for 30 seconds at the end of every30-minute period until the chiller is started.IMPORTANT: A field-supplied water temperature controlsystem for condenser water should be installed. The systemshould maintain the leaving condenser water temperature ata temperature that is at least 20° F (11° C) above the leavingchilled water temperature. While the tower fan relay outputsdescribed above are not a substitute for a complete con-denser water control system, they can serve as useful inputsto such a system.