Flooded type water cooled screw chiller (PCB Control)
103
Oil change
1. Change oil periodically: Check the lubrication oil for every 10,000 hours of continuous running. For the
first operation of the compressor, it is recommended to change oil and clean oil filter after running at
2,000 hours. Check the system whether clean or not and then change the oil every 20,000 hours or after
3 years of continuous running while the system is operated under good condition.
2. Avoid the debris or swarf clogging oil filter, this may caused bearings failure. The oil pressure
differential switch will trip when the oil pressure differential reaches the critical point (default: 150kPa).
The compressor will automatically shut down to prevent the bearings from getting damaged due to the
lack of lubricating oil.
Caution
Compressor oil is pressurized. Use proper safety precautions when relieving pressure.
Oil Filter Maintenance
Each compressor has its own internal oil filter and each circuit also has an in-line external filter located
under the external oil separator. The internal oil filter pressure drop should be checked and filter
changed (if necessary) after the initial 2000 hours of compressor operation. Oil line pressure loss is
monitored by the control and reported for each compressor as the oil filter pressure drop.
Normally the pressure differential (discharge pressure minus oil pressure) is typically less than 150kPa
for a system with clean internal and external filters. To determine the oil pressure drop due to the oil lines
and external filter only, connect a gage to the oil pressure bleed port. Compare this value to the
discharge pressure read at the touch screen. If this value exceeds 150 kPa, replace the external filter.
Moisture-Liquid Indicator
Clear flow of liquid refrigerant indicates sufficient charge in the system. Note, however, that bubbles in
the sight glass do not necessarily indicate insufficient charge. Moisture in the system is measured in
parts per million (ppm), changes of color of indicator are:
Green
—moisture is below 80 ppm;
Yellow-green (chartreuse)
—80 to 225 ppm (caution);
Yellow (wet)
—above 225 ppm.
Change filter drier at the first sign of moisture in the system.
IMPORTANT:
Unit must in operation for at least 12 hours before moisture indicator can give an accurate
reading. With the unit running, the indicating element must be in contact with liquid refrigerant to give
true reading.
Relief Devices
Pressure relief valves
Relief valves are installed on evaporator, condenser and oil separator. These valves are designed to
relieve if an abnormal pressure condition arises. Relief valves on condenser relieve at 2.07MPa. These
valves should not be capped. If a valve relieves, it should be replaced. If not replaced, it may relieve at a
lower pressure compared to the set point, or leak due to trapped dirt from the system which may prevent
resealing.
