Lag Chiller Shutdown Requirements
The following condit ion s must be met in order for the lag c hi ller 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 temper ature is less than t he CONTROL POINT plus 1/2 of the
WATER/BRINE DEADBAND.
3. The configured LAG STO P TIMER entry has elapse d. 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 DEADBA ND and the lead chiller
COMPRESSOR MOTOR LOAD is less than the lead chiller percent capacity plus 15%. The
timer is ignored if the ch ill ed water temperature re ac he s 3° F (1.67° C) below the
CONTROL POINT and the lead chiller COMPRESSOR MOTOR LOAD value is less than
the lead chiller percen t capacity plus 15%.
Faulted Chiller Operation
If the lead chill er shuts down on a n alarm (*) conditio n, it stops commun ication to the lag a nd
standby chillers. A fter 30 seconds, the la g chiller will now beco me the acting lead chille r and will
start and stop the standby chiller, if necessary.