Flooded type water cooled screw chiller (PCB Control) MCAC-CTSM-2012-11
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2.4 Removal and Service of Key Parts
Annual Startup
This is a good time to check all the motor winding resistance to ground. Semi-annual checking and
recording of this resistance will provide a record of any deterioration of the winding insulation. All new
units have well over 100 MΩ resistances between any motor terminal and ground.
1. The control circuit must be energized at all times, except during service. If the control circuit has been
off and oil is cool, energize oil heaters and allow 8 hours for heater to remove refrigerant from the oil
before starting.
2. Check and tighten all electrical connections.
3. Replace the drain plug in the cooling tower pump if it was removed at shutdown time the previous
season.
4. Install fuses in main disconnect switch (if removed).
5. Reconnect water lines and turn on supply water. Flush condenser and check for leaks.
Annual Shutdown
Where the chiller can be subject to freezing temperatures, the condenser and chiller must be drained of
all water. Dry air blown through the condenser will aid in forcing all water out and decreasing the
corrosion. Water permitted to remain in the piping and vessels can rupture these parts if subjected to
freezing temperature.
If the chiller is used in areas where the ambient temperature will fall below 0℃, forced circulation of
antifreeze through the water circuits is one method of avoiding freeze up.
1. Take measures to prevent the shutoff valve in the water supply line from being accidentally turned on.
2. If a cooling tower is used, and if the water pump will be exposed to freezing temperature, be sure to
remove the pump drain plug and leave it out so any water that can accumulate will drain away.
3. Open the compressor disconnect switch, and remove the fuses.
4. Check for corrosion and clean and paint rusted surfaces.
5. Clean and flush water tower for all units operating on a water tower. It should be recognized that
atmospheric air contains many contaminants that increase the need for proper water treatment. The
use of untreated water can result in corrosion, erosion, sliming, scaling or algae formation. It is
recommended that the service of a reliable water treatment company be used.
6. Remove condenser heads at least once a year to inspect the condenser tubes and clean if required.
Recommended maintenance schedule
This chapter shows the preventive maintenance of Midea screw chiller. Correct maintenance and timely
service will make the chiller in the best condition and with best performance, beside, it can prolong the
lifespan of chiller.
The customer has responsibility to appoint qualified equipment management engineer and
specially-assigned operator to do the daily and scheduled maintenance. The repair work should be done
by big maintenance agency that is qualified to do the job. It’s better to make maintenance agreement
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