Carrier 17/19EX - Manual (Page 103)

If the lag chiller faults when the lead chiller is also faulted, the standby chiller reverts to a
stand-alone CCN mode of operation.
If the lead chiller is in an alarm (*) condition (as shown on the LID panel), the RESET softkey
is pressed to clear the alarm, and the chiller is placed in the CCN mode, the lead chiller will now
communicate and monitor the RUN STATUS of the lag and standby chillers. If both the lag and
standby chillers are running, the lead chiller will not attempt to start and will not assume the role
of lead chiller until either the lag or standby chiller shuts down. If only one chiller is running, the
lead chiller will wait for a start request from the operating chiller. When the configured lead
chiller starts, it assumes its role as lead chiller.
Load Balancing
When the LOAD BALANCE OPTION is enabled, the lead chiller will set the ACTIVE DE-
MAND LIMIT in the lag chiller to the lead chiller’s COMPRESSOR MOTOR LOAD value. This
value has limits of 40% to 100%. When setting the lag chiller ACTIVE DEMAND LIMIT, the
CONTROL POINT shall be modified to a value of 3° F (1.67° C) less than the lead chiller’s
CONTROL POINT value. If the LOAD BALANCE OPTION is disabled, the ACTIVE DEMAND
LIMIT and the CONTROL POINT are forced to the same value as the lead chiller.