Carrier PIC 5+ - Master Slave Control; Oil EXV Control; Pumpdown;Lockout; Trending

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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 congured
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 congure which one’s condenser is in
downstream. The master chiller shall monitor all external
commands as start/stop, demand limiting or setpoint
conguration.
The master slave function shall provide the ability to select
a lead chiller among the master and the slave chillers.
Selection shall be based on the delta between the master and
the slave run hours and shall try to optimize the runtime
hours. 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 rstly 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 congure Middle Sensor
Option in Master Slave Cong table.
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If the chiller system is equipped with Oil EXV control valve,
and Oil EXV valve option in CONF_OPT table is
ENABLED, then PIC 5+ 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 congurations
should be in place. They are Oil Temp High Threshold and
Oil Temp Low Threshold.
1 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 1 minute after compressor starts or shutdown
completed, the oil EXV valve should be in fully closed
position
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The Pumpdown/Lockout feature prevents compressor start-
up when there is no refrigerant in the chiller. This function
is password-protected, user can access to this function via
maintenance menu
When using Pumpdown/Lockout function, will observe freeze
up precautions whiling using external pumpout to remove
refrigerant from chiller:
- Start water pumps and conrm ows
- Monitor Evaporator pressure, Condenser pressure,
Evaporator refrigerant temperature during pumpout
procedures
- Turn pumps off after pumpdown
- Proceed to locks out compressor
The Terminate Lockout feature ends the Pumpdown/Lockout
after refrigerant is added:
- Starts pumps and conrm ows
- Monitor Evaporator pressure, Condenser pressure,
Evaporator temperature during charging process
- Terminates compressor lockout
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Accessing trending conguration screen does not require any
specic login level.
Just browse to Main Menu - > Trendings
Conguration is saved using the appropriate button:
The Trending screens are made to adjust and display the
trending curves recorded by the system.