Carrier 19DV Series Installation, Operation And Maintenance Instructions page 63

Fig 35 – Operating mode / Local On
Note: Prior to start-up, the start-to-start timer and the stop-to-start timer must have elapsed and all alarms must be
cleared.
When start-up is initiated, the status screen displays the startup progress and the Start/Stop icon blinks green.
Once local start-up begins, the PIC5+ control system performs a series of prestart tests to verify that all prestart
alerts and safeties are within acceptable limits. Table XX shows appropriate Prestart Alerts/Alarms conditions. If a
test is not successful, the start-up is delayed or aborted. If the tests are successful, the start-up will be in progress
and the COMPRESSOR RUN STATUS shall be "Startup." The control shall then energize the chilled water/brine
pump relay.
Five seconds later, the condenser pump relay energizes. Thirty seconds later the PIC5+ control system 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 PIC5+ control system turns off the
condenser pump relay and goes into a Recycle mode.
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 PIC5+ control system closes the
vanes. If the vanes are closed and the refrigerant pump pressure difference is less than 34.5 kPa, the refrigerant
pump relay energizes.
The PIC5+ control system then waits until the refrigerant pressure (REF PRESS VERIFY TIME, operator-
configured, default of 40 seconds) reaches a maximum of 82.7 kPa. After refrigerant pressure is verified, if high
side float chamber has adequate liquid level, refrigerant pump will be kept ON for 20 seconds for pre-lube; if not,
refrigerant pump will be kept ON pumping refrigerant from evaporator to the high side float chamber until liquid
level is satisfied. Upon pre-lube satisfied the compressor start relay is energized.
Compressor on-time and service on-time 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 PIC5+ control system aborting the start
and displaying the applicable prestart alert alarm state number near the bottom of the home screen on the HMI
panel. A prestart failure does not advance the STARTS IN 12 HOURS counter. Any failure after the compressor
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 display.
The minimum time to complete the entire prestart sequence is approximately 185 seconds. See Fig. 36 for normal
start-up timing sequence. See Table 15 for a list of prestart checks.
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