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5.31. Master Slave Control
The control shall provide the capability to operate 2 chillers in Master/Slave mode. Slave chiller should
be set to NETWORK mode and controlled by Master chiller.
The two chillers in Master/Slave control can be configured to be in parallel or in series mode. When they
are in series mode, master chiller’s evaporator must be in downstream, and user is able to configure
which one’s condenser is in downstream. The master chiller shall monitor all external commands as
start/stop, demand limiting or setpoint configuration.
The controller can decide the lead/leg chiller according to Master Lead Lag Select. If this function is
unused then, the lead chiller shall always the master and should be changed to lag when it failed.
The lead chiller shall always be started firstly and the lag chiller shall be maintained at zero percent
capacity. When the lead chiller cannot be loaded anymore then the lag start timer is started.
The lag chiller shall always be stopped prior to lead chiller.
If a communication failure is detected between the master and the slave then, all master/slave functions
shall be disabled and chillers shall return to standalone operations until communication is reestablished.
If Middle sensor is installed, user can configure Middle Sensor Option in Master Slave Config table.
5.32. Oil EXV Control
If the chiller system is equipped with Oil EXV control valve, and Oil EXV valve option in CONF_OPT
table is ENABLED, then Carrier® SmartVu
TM
control system will control the opening of Oil EXV valve to
maintain the oil supply temperature. The output of this valve is 4-20mA type.
Before using this function, the appropriate configurations should be in place. They are Oil Temp High
Threshold and Oil Temp Low Threshold.
One minute after compressor starts, if oil supply temperature > Oil Temp High Threshold, oil EXV valve
should be in fully opened position; if oil supply temperature < Oil Temp low Threshold, oil EXV valve
should be in fully closed position; otherwise, oil EXV valve position will be calculated according to oil
supply temperature.
During one minute after compressor starts or shutdown completed, the oil EXV valve should be in fully
closed position
5.33. Hydraulic Option Control
5.33.1. Water Flow Measurement
Carrier® SmartVu
TM
Controller provides the function of measuring water flow rate.
It can compute the water flow rate from the input signal sent from the evaporator/condenser water flow
sensor (4-20ma) to the IOB if water flow meter is installed.
Step 1: Set ”Option 2” -> ”IOB4 Option” as ”Yes”.
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