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5.5
Stopping procedures
5.5.1
Stopping for a brief period
In automatic mode Unisab III will occasionally stop the chiller depending on the cooling require-
ment. This is normal and does not require any action by the operator of the plant.
The chiller can be stopped manually on Unisab III at any capacity setting. However, under normal
conditions, it is recommended to reduce capacity to a minimum before stopping the compressor.
Leave all valves in their "in-operation positions" unless servicing or repair work is to be per-
formed. Do not turn off power to the chiller unit as the oil heater must be connected to keep the
correct oil temperature.
Caution!
Wire connections to the motor and VSD must not be touched immediately after the chiller is pow-
ered down as the capacitors in the VSD may still be charged. Read the warning label on the VSD.
5.5.2
Shutting down for a long standstill period
Follow the Stopping for a brief period instructions and:
1.
Turn of the oil heater.
2.
Close suction and discharge valves.
3.
Rotate the motor and compressor (weekly/monthly according to below).
4.
If the compressor is water-cooled, drain of the water.
To reduce the risk of bearing damage, it is recommended to rotate (to a new position) the motor
and compressor on a monthly basis. If the chiller unit is exposed to vibrations during a long shut-
down period, the position should be changed weekly. Avoid high vibration level.
5.6
Shutdowns and alarms
5.6.1
Operating state
Experience has shown that variations in pressures and temperatures within the cooling cycle can
provide information about the operating state of the refrigeration plant.
In particular, suction and condensing pressures, as well as the temperatures of suction and pres-
sure gas, can provide important information.
Often, small changes in the variable pressures and temperatures are sufficient to create consider-
able changes in the operating conditions.
It is therefore very important to use a logbook as mentioned in subsection 5.4.2 Monitoring of op-
eration. If a refrigeration plant is not operating in optimal conditions, the economy of the plant will
not be optimal either.
Irregularities in the plant will often cause changes in the operating conditions but not make the
plant stop. Consequently, the operating state of a refrigeration plant must be checked at regular
intervals.
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Operating instructions
Operating manual - ComPAC
011769 en 2020.03
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