Operation Sequence Of Operation - LG RCAW Operation & Maintenance Manual

Operation
OPERATION
Sequence of Operation
The sequence of the operation is depicted by the flow chart in the below. When the start is in effect, the condenser fan
and water pump run concurrently. Additionally, for the minimum load position of the compressor, the MV1 is turned on.
After condenser fan feedback delay, the feedback inputs from the contactors are checked. The PLC shutdown the chiller
if there is problem with the contactor feedback. Similarly, 9 seconds after the water pump run, water flow is checked.
When there is no problem with the water flow, startup delay is initiated. For the 30~60 second delay, chilled water leav-
ing temperature is checked whether the water temperature is enough high to run the compressor.
When the PLC decides to turn on the compressor, it starts the compressor in star-start, and transits to delta-start after 4
seconds. During starting the compressor, the compressor contactors are also checked whether there is any problem
with the feedback from the contactors, and SV1 oil solenoid valve is opened for proper oil circulation.
After the start, normal controls are initiated. The normal controls include capacity control, mid pressure refrigerant con-
trol for motor cooling, condenser fan control, and alarm control.
When the chiller is requested to be stopped, the load condition of the compressor is changed into minimum load position
by turning on MV1 and Turning off MV2 and MV3. After 60 second of shutdown delay, the compressor is stopped.
Even with the stop of the compressor, the chilled water pump still runs for 4-10 minutes to protect the compressor from
frequent restart and to withdraw latent heat from evaporator of the chiller.
The shutdown delay and water pump run delay can be configured in delay setting screen of the HMI unit.
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