n Operation Sequence
When the chiller starts the water pumps will start to operate at the same time. Also the SV1 will be turned on at
minimum load location of the compressor. Also after the water pumps operates for 9 seconds, the chiller cold
water and cooling water flow will be checked.
If there is any issue with the water flow, the start will be delayed. When the operation is delayed for 30-60 sec-
onds, the cold water leaving temperature and cooling water leaving temperature will be checked to validate
whether the water temperatures are high enough to operate the compressor. When the PLC decides to turn on
the compressor, it will start the compressor at start and transmit to delta start in 4 seconds. When the compres-
sor starts, the compressor contactor checks to validate if there is any issue in the feedback from the contactor
and also checks whether the SV1 oil solenoid valve is opened for appropriate oil circulation.
After start, the normal controller will be initialized. Normal control includes capacity control, mid pressure cool-
ing control to cool the motor and the alarm control. When the chiller must be stopped, the operating condition of
the compressor will turn on SV1 and SV2 to change to minimum capacity location. 60 seconds after the stop-
ping is delayed, the compressor will be stopped.
Even when the compressor is stopped, the chilled water pump will prevent the compressor from restarting and
operate for another 4-10 minutes to remove the latent heat from the evaporator of the chiller.
Stop delay and water pump operation delay can be set from the delay setting screen of HMI.
Delays of control for the chiller are two essential delays. One is the Start delay from the indicated Stop and the
other is the oil preheat delay. Start delay from Stop is the period between the time the compressor is stopped
and the compressor is restarted. The basic setting of delay is 10 minutes. Delay is designed to protect the fre-
quent re-operation. The other delay, oil preheat delay, only operates after the power is initialized. Delay can be
set through the user setting of HMI device. Delay is designed to prevent the oil from circulating incorrectly in the
cooling cycle of the chiller in low surrounding condition.
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Operation & Maintenance Manual