START-UP/SHUTDOWN/
RECYCLE SEQUENCE (Fig. 26)
Local Start-Up — Local start-up (or a manual start-up) is
initiated by pressing the LOCAL menu softkey on the default CVC/ICVC screen. Local start-up can proceed when the chiller schedule indicates that the current time and date have been established as a run time and date, and after the internal 15-minute start-to-start and the 1-minute stop-to-start inhibit timers have expired. These timers are represented in the START INHIBIT TIMER and can be viewed on the MAINSTAT screen and DEFAULT screen. The timer must expire before the chiller will start. If the timers have not expired the RUN STATUS pa- rameter on the MAINSTAT screen now reads TIMEOUT.
NOTE: The time schedule is said to be “occupied” if the OCCUPIED ? parameter on the MAINSTAT screen is set to YES. For more information on occupancy schedules, see the sections on Time Schedule Operation (page 20), Occupancy Schedule (page 34), and To Prevent Accidental Start-Up (page 65), and Fig. 19.
If the OCCUPIED ? parameter on the MAINSTAT screen is set to NO, the chiller can be forced to start as follows. From
the default CVC/ICVC screen, press the MENU and
STATUS softkeys. Scroll to highlight MAINSTAT. Press the SELECT softkey. Scroll to highlight CHILLER START/STOP.
Press the START softkey to override the schedule and start the chiller.
NOTE: The chiller will continue to run until this forced start is released, regardless of the programmed schedule. To release the forced start, highlight CHILLER START/STOP from the
MAINSTAT screen and press the RELEASE softkey. This action returns the chiller to the start and stop times established by the schedule.
The chiller may also be started by overriding the time schedule. From the default screen, press the MENU and
SCHEDULE softkeys. Scroll down and select the current schedule. Select OVERRIDE, and set the desired override time.
Another condition for start-up must be met for chillers that have the REMOTE CONTACTS OPTION on the EQUIP- MENT SERVICE screen set to ENABLE. For these chillers, the REMOTE START CONTACT parameter on the MAIN- STAT screen must be CLOSED. From the CVC/ICVC default screen, press the MENU and STATUS softkeys. Scroll to highlight MAINSTAT and press the SELECT softkey. Scroll down the MAINSTAT screen to highlight REMOTE START CONTACT and press the SELECT softkey. Then, press the CLOSE softkey. To end the override, select REMOTE CON- TACTS INPUT and press the RELEASE softkey.
Once local start-up begins, the PIC II performs a series of pre-start tests to verify that all pre-start alerts and safeties are within the limits shown in Table 4. The RUN STATUS parame- ter on the MAINSTAT screen line now reads PRESTART. If a test is not successful, the start-up is delayed or aborted. If the tests are successful, the chilled water/brine pump relay energiz- es, and the MAINSTAT screen line now reads STARTUP.
Five seconds later, the condenser pump relay energizes. Thirty seconds later the PIC II monitors the chilled water and condenser water flow devices and waits until the WATER FLOW VERIFY TIME (operator-configured, default 5 minutes) expires to confirm flow. After flow is verified, the chilled water temperature is compared to CONTROL POINT plus 1/2 CHILLED WATER DEADBAND. If the temperature is less than or equal to this value, the PIC II turns off the condenser pump relay and goes into a RECYCLE mode.
NOTE: Units equipped with ICVC are not available with fac- tory installed chilled water or condenser water flow devices (available as an accessory for use with the CCM Control board).
If the water/brine temperature is high enough, the start-up sequence continues and checks the guide vane position. If the guide vanes are more than 4% open, the start-up waits until the PIC II closes the vanes. If the vanes are closed and the oil pump pressure is less than 4 psi (28 kPa), the oil pump relay energiz- es. The PIC II then waits until the oil pressure (OIL PRESS VERIFY TIME, operator-configured, default of 40 seconds) reaches a maximum of 18 psi (124 kPa). After oil pressure is verified, the PIC II waits 40 seconds, and the compressor start relay (1CR) energizes to start the compressor.
Compressor ontime and service ontime timers start, and the compressor STARTS IN 12 HOURS counter and the number of starts over a 12-hour period counter advance by one.
Failure to verify any of the requirements up to this point will result in the PIC II aborting the start and displaying the applica- ble pre-start mode of failure on the CVC/ICVC default screen. A pre-start failure does not advance the STARTS IN 12 HOURS counter. Any failure after the 1CR relay has energized results in a safety shutdown, advances the starts in 12 hours counter by one, and displays the applicable shutdown status on the CVC/ ICVC display.
A— START INITIATED: Pre-start checks are made; evaporator pump started.
B— Condenser water pump started (5 seconds after A).
C— Water flows verified (30 seconds to 5 minutes maximum after B). Chilled water temperatures checked against control point. Guide vanes checked for closure. Oil pump started; tower fan control enabled.
D— Oil pressure verified (15 seconds minimum, 300 seconds maximum after C).
E— Compressor motor starts; compressor ontime and service ontime start, 15-minute inhibit timer starts (10 seconds after D), total com- pressor starts advances by one, and the number of starts over a 12-hour period advances by one.
F— SHUTDOWN INITIATED — Compressor motor stops; compressor
ontime and service ontime stop, and 1-minute inhibit timer starts.
G— Oil pump and evaporator pumps deenergized (60 seconds after F). Condenser pump and tower fan control may continue to operate if condenser pressure is high. Evaporator pump may continue if in RECYCLE mode.
O/A — Restart permitted (both inhibit timers expired: minimum of 15 minutes after E; minimum of 1 minute after F).
Fig. 26 — Control Sequence
