Carrier 17/19EX - Manual (Page 102)

Lag Chiller Shutdown Requirements
The following conditions must be met in order for the lag chiller to be stopped.
1. Lead chiller COMPRESSOR MOTOR LOAD value is less than the lead chiller percent
capacity plus 15%.
Note: Lead chiller percent capacity = 100 – LAG PERCENT CAPACITY
The LAG PERCENT CAPACITY value is configured on the Lead/Lag Configuration screen.
2. The lead chiller chilled water temperature is less than the CONTROL POINT plus 1/2 of the
WATER/BRINE DEADBAND.
3. The configured LAG STOP TIMER entry has elapsed. The LAG STOP TIMER is started
when the CHILLED WATER TEMPERATURE is less than the CHILLED WATER
CONTROL POINT plus 1/2 of the WATER/BRINE DEADBAND and the lead chiller
COMPRESSOR MOTOR LOAD is less than the lead chiller percent capacity plus 15%. The
timer is ignored if the chilled water temperature reaches 3° F (1.67° C) below the
CONTROL POINT and the lead chiller COMPRESSOR MOTOR LOAD value is less than
the lead chiller percent capacity plus 15%.
Faulted Chiller Operation
If the lead chiller shuts down on an alarm (*) condition, it stops communication to the lag and
standby chillers. After 30 seconds, the lag chiller will now become the acting lead chiller and will
start and stop the standby chiller, if necessary.