CHAPTER 3 MAINTENANCE PROCEDURES
FC5515R Centrifuge Service Manual
3-7
Ohaus Corporation www.ohaus.com
3.5 Refrigerated System.
3.5.1 Functional description of the cooling system
The expansion valve regulates how much refrigerant is being led to the evaporator. The compressor makes the
refrigerant available in the collective dryer. A sensor is continuously measuring the temperature at the evaporator
output. Through this, the injection nozzle of the expansion valve is controlled and the evaporator is supplied with the
max. Necessary amount of refrigerant. Therefore, maximum capability of the refrigeration system can be reached at
any status of operation.
As soon as the required pre-set temperature is reached, the compressor will switch off. When the
temperature rises again, the compressor will switch on again. The response time of the compressor is controlled with
a microprocessor control. The processor receives the chamber temperature data through a temperature sensor placed
in the rotor chamber. As the actual sample temperature may not be identical to the temperature measured in the rotor
chamber, the microprocessor will calculate the sample temperature for the rotor in use. This temperature value is
indicated in the temperature display. The temperature adjustment of the microprocessor is based on this calculated
temperature value. Therefore, the user always gets the exactly requested sample temperature (± 2° C).
3.5.2
Refrigeration scheme
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Figure 53: Refrigeration scheme.
