and go into a RECYCLE mode. If the water/brine tempera- ture is high enough, the start-up sequence continues on to check the guide vane position. If the guide vanes are more than 6% open, the start-up waits until the PIC closes the vanes. If the vanes are closed, and the oil pump pressure is less than 3 psid (21 kPad), the oil pump relay will then be en- ergized. The PIC then waits until the OIL PRESS (Pressure) VERIFY TIME (operator con®gured, default 15 seconds) for oil pressure to reach 18 psid (124 kPad). After oil pressure is veri®ed, the PIC waits 15 seconds, and then the compres- sor start relay (1CR) is energized to start the compressor. Compressor ontime and service ontime timers start and the compressor starts counter and the number of starts over a 12-hour period counter are advanced by one.
Failure to verify any of the requirements up to this point will result in the PIC aborting the start and displaying the applicable pre-start mode of failure on the LID default screen. A pre-start failure does not advance the starts in 12 hours counter. Any failure, after the 1CR relay has energized, re- sults in a safety shutdown, energizes the alarm light, and dis- plays the applicable shutdown status on the LID display.
Shutdown Sequence Ð Shutdown of the chiller can occur if any of the following events happen:
·the STOP button is pressed for at least one second (the alarm light will blink once to con®rm stop command)
·recycle condition is present (see Chilled Water Recycle Mode section)
·time schedule has gone into UNOCCUPIED mode (chiller protective limit has been reached and chiller is in alarm)
·the start/stop status is overridden to stop from the CCN network or the LID
When a stop signal occurs, the shutdown sequence ®rst stops the compressor by deactivating the start relay. A status message of ``SHUTDOWN IN PROGRESS, COMPRES- SOR DEENERGIZED'' is displayed. Compressor ontime and service ontime stop. The guide vanes are then brought to the closed position. The oil pump relay and the chilled water/ brine pump relay are shut down 60 seconds after the com- pressor stops. The condenser water pump will be shut down when the CONDENSER REFRIGERANT TEMP is less than the CONDENSER PRESSURE OVERRIDE minus 5 psi (34 kPa) or is less than or equal to the ENTERING CONDENSER WATER TEMP plus 3° F (2° C). The stop- to-start timer will now begin to count down. If the start-to- start timer is still greater than the value of the start-to-stop timer, then this time is now displayed on the LID.
Certain conditions during shutdown will change this sequence:
·if the COMPRESSOR MOTOR LOAD is greater than 10% after shutdown, or the starter contacts remain energized, the oil pump and chilled water pump remain energized and the alarm is displayed
·if the ENTERING CONDENSER WATER temperature is greater than 115 F (46 C) at shutdown, the condenser pump will be deenergized after the 1CR compressor start relay
·if the chiller shuts down due to low refrigerant tempera- ture, the chilled water pump will stay running until the LEAVING CHILLED WATER is greater than CONTROL POINT, plus 5° F (3° C)
Automatic Soft Stop Amps Threshold (PSIO Soft- ware Version 09 and Higher) Ð The SOFT STOP AMPS THRESHOLD closes the guide vanes of the com- pressor automatically when a non-recycle, non-alarm stop signal occurs before the compressor motor is deenergized.
If the STOP button is pressed, the guide vanes close to a preset amperage percent or until the guide vane is less than 2% open. The compressor will then shut off.
If the chiller enters an alarm state or if the compressor enters a RECYCLE mode, the compressor will be de- energized immediately.
To activate SOFT STOP AMPS THRESHOLD, view the bottom of Service1 table. Set the SOFT STOP AMPS THRESHOLD value to the percentage amps at which the motor will shut down. The default setting is 100% amps (no Soft Stop).
When the SOFT STOP AMPS THRESHOLD is being applied, a status message ``SHUTDOWN IN PROGRESS, COMPRESSOR UNLOADING'' is shown.
Chilled Water Recycle Mode Ð The chiller may cycle off and wait until the load increases to restart again when the compressor is running in a lightly loaded condition. This cycling of the chiller is normal and is known as recycle. A recycle shutdown is initiated when any of the following con- ditions are true:
·when in LCW control, the difference between the LEAV- ING CHILLED WATER temperature and ENTERING CHILLED WATER temperature is less than the RECYCLE SHUTDOWN DELTA T (found in the Service1 table) and the LEAVING CHILLED WATER TEMP is below the CONTROL POINT, and the CONTROL POINT has not increased in the last 5 minutes.
·when ECW CONTROL OPTION is enabled, the difference between the ENTERING CHILLED WATER temperature and the LEAVING CHILLED WATER temperature is less than the RECYCLE SHUTDOWN DELTA T (found in the Service1 table) and the ENTERING CHILLED WATER TEMPERATURE is below the CONTROL POINT, and the CONTROL POINT has not increased in the last 5 minutes.
·when the LEAVING CHILLED WATER temperature is within 3° F (2° C) of the BRINE REFRIG TRIPPOINT
When the chiller is in RECYCLE mode, the chilled water pump relay remains energized so that the chilled water tem- perature can be monitored for increasing load. The recycle control uses RECYCLE RESTART DELTA T to check when the compressor should be restarted. This is an operator- con®gured function which defaults to 5° F (3° C). This value is viewed/modi®ed on the Service1 table. The compressor will restart when:
·in LCW CONTROL the LEAVING CHILLED WATER tem- perature is greater than the CONTROL POINT plus the RECYCLE RESTART DELTA T; or
·in ECW CONTROL, the ENTERING CHILLED WATER temperature is greater than the CONTROL POINT plus the
RECYCLE RESTART DELTA T
Once these conditions are met, the compressor will ini- tiate a start-up, with a normal start-up sequence.
An alert condition may be generated if 5 or more RECYCLE STARTUPs occur in less than 4 hours. This excessive recycling can reduce chiller life. Compressor re- cycling due to extremely low loads should be reduced. To reduce compressor recycling, use the time schedule to shut the chiller down during low load operation or increase the chiller load by running the fan systems. If the hot gas bypass is installed, adjust the values to ensure that hot gas is ener- gized during light load conditions. Increase the RECYCLE RESTART DELTA T on the Service1 table to lengthen the time between restarts.
The chiller should not be operated below design mini- mum load without a hot gas bypass installed on the chiller.
