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Lag Chiller Start-Up Requirements
Before the lag chiller can be started, the following conditions must be met:
1. Lead chiller ramp loading must be complete.
2. Lead chiller CHILLED WATER temperature must be greater than the CONTROL POINT
plus 1/2 the WATER/BRINE DEADBAND.
Note: The chilled water temperature sensor may be the leaving chilled water sensor, the return
water sensor, the common supply water sensor, or the common return water sensor,
depending on which options are configured and enabled.
3. Lead chiller ACTIVE DEMAND LIMIT value must be greater than 95% of full load amps.
4. Lead chiller temperature pulldown rate of the CHILLED WATER temperature is less than
0.5° F (0.27° C) per minute.
5. The lag chiller status indicates it is in CCN mode and is not faulted. If the current lag chiller
is in an alarm condition, then the standby chiller becomes the active lag chiller, if it is
configured and available.
6. The configured LAG START TIMER entry has elapsed. The LAG START TIMER shall be
started when the lead chiller ramp loading is completed. The LAG STARTTIMER entry is
accessed by selecting Lead/Lag from the Equipment Configuration table of the Service
menu.
When all of the above requirements have been met, the lag chiller is forced to a START
mode. The PIC control then monitors the lag chiller for a successful start. If the lag chiller fails to
start, the standby chiller, if configured, is started.