Condenser Freeze Prevention — This control algo- rithm helps prevent condenser tube
When the CONDENSER REFRIG TEMP is less than or equal to the CONDENSER FREEZE POINT, the CONDENS- ER WATER PUMP is energized until the CONDENSER RE- FRIG TEMP is greater than the CONDENSER FREEZE POINT plus 5° F (2.7° C) and the ENTERING CONDENSER WATER TEMPERATURE is less than or equal to the CON- DENSER FREEZE POINT. An alarm is generated if the chiller is in PUMPDOWN mode and the pump is energized. An alert is generated if the chiller is not in PUMPDOWN mode and the pump is energized. If the chiller is in RECYCLE SHUT- DOWN mode, the mode will transition to a
Evaporator Freeze Protection (ICVC only) — A
refrigerant temperature sensor is installed at the bottom of the cooler to provide redundant freeze protection. In place of the cooler and condenser water pressure transducer inputs on the CCM is a 4.3k ohm resister and a jumper lead. When the EVAPORATOR REFRIGERANT TEMPERATURE is less than the EVAP REFRIG TRIPPOINT plus the REFRIG OVERRIDE DELTA T (configurable from 2° to 5°), state 122 will be displayed and a capacity override will occur. If the EVAPORATOR REFRIG TEMP is equal to or less than the EVAP Refrig TRIPPOINT, Protective Limit ALARM STATE 232 will be displayed and the unit will shut down.
Tower Fan Relay Low and High — Low condenser water temperature can cause the chiller to shut down when re- frigerant temperature is low. The tower fan relays, located in the starter, are controlled by the PIC II to energize and deener- gize as the pressure differential between cooler and condenser vessels changes. This prevents low condenser water tempera- ture and maximizes chiller efficiency. The tower fan relay can only accomplish this if the relay has been added to the cooling tower temperature controller.
The tower fan relay low is turned on whenever the condens- er water pump is running, flow is verified, and the difference between cooler and condenser pressure is more than 30 psid (207 kPad) for entering condenser water temperature greater than 65 F (18.3 C).
The tower fan relay low is turned off when the condenser pump is off, flow is stopped, or the cooler refrigerant tempera- ture is less than the override temperature for ENTERING CON- DENSER WATER temperature less than 62 F (16.7 C), or the differential pressure is less than 25 psid (172.4 kPad) for enter- ing condenser water less than 80 F (27 C).
The tower fan relay high is turned on whenever the condenser water pump is running, flow is verified and the dif- ference between cooler and condenser pressure is more than 35 psid (241.3 kPa) for entering condenser water temperature greater than the TOWER FAN HIGH SETPOINT (SETPOINT menu, default 75 F [23.9 C]).
The tower fan relay high is turned off when the condenser pump is off, flow is stopped, or the cooler refrigerant tempera- ture is less than the override temperature and ENTERING CONDENSER WATER is less than 70 F (21.1 C), or the differ- ence between cooler and condenser pressure is less than 28 Psid (193 kPa), or ENTERING CONDENSER WATER temperature is less than TOWER FAN HIGH SETPOINT minus 3 F
The TOWER FAN RELAY LOW and HIGH parameters are accessed from the STARTUP screen.
IMPORTANT: A
The tower fan relay control is not a substitute for a con- denser water temperature control. When used with a water temperature control system, the tower fan relay control can be used to help prevent low condenser water temperatures.
Auto. Restart After Power Failure — This option may be enabled or disabled and may be viewed or modified on the OPTIONS screen, which is accessed from the EQUIP- MENT CONFIGURATION table. If the AUTO. RESTART OPTION is enabled, the chiller will start up automatically after a power failure has occurred (after a single cycle dropout; low, high, or loss of voltage; and the power is within ± 15% of nor- mal). The 15- and
When power is restored after the power failure and if the compressor had been running, the oil pump will energize for one minute before energizing the cooler pump. AUTO. RESTART will then continue like a normal
If power to the CVC/ICVC module has been off for more than 3 hours or the timeclock has been set for the first time, start the compressor with the slowest
The oil pump is energized occasionally during the time the oil is being brought up to proper temperature in order to elimi- nate refrigerant that has migrated to the oil sump during the power failure. The pump turns on for 60 seconds at the end of every
Water/Brine Reset — Three types of chilled water or brine reset are available and can be viewed or modified on the TEMP_CTL screen, which is accessed from the EQUIPMENT SERVICE table.
The CVC/ICVC default screen indicates when the chilled water reset is active. TEMPERATURE RESET on the MAIN- STAT screen indicates the amount of reset. The CONTROL POINT will be determined by adding the TEMPERATURE RESET to the SETPOINT.
To activate a reset type, access the TEMP_CTL screen and input all configuration information for that reset type. Then, in- put the reset type number (1, 2, or 3) in the SELECT/ENABLE RESET TYPE input line.
RESET TYPE 1: 4 to 20 mA (1 to 5 vdc) TEMPERATURE RESET — Reset Type 1 is an automatic chilled water temper- ature reset based on a remote temperature sensor input config- ured for either an externally powered 4 to 20 mA or a 1 to 5 vdc signal. Reset Type 1 permits up to ±30 F (±16 C) of automatic reset to the chilled water set point.
The auto, chilled water reset is hardwired to terminals
RESET TYPE 2: REMOTE TEMPERATURE RESET — Reset Type 2 is an automatic chilled water temperature reset based on a remote temperature sensor input signal. Reset Type 2 permits ± 30° F (± 16° C) of automatic reset to the set point based on a temperature sensor wired to the CCM module
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