18
1. Strainer
2. From evaporator
3. To compressor motor bearings
4. Filter
5. From high side float chamber
6. Filter
7. Actuator, condenser valve
8. Pump discharge
9. Pump suction
10. Actuator and 3 way valve, cooler valve
11. Pump
Figure 6 – Refrigerant lubrication Assembly
2.5.5.3 Motor cooling system
The motor is cooled by liquid refrigerant taken from the bottom of the high side condenser float chamber.
Refrigerant flow is maintained by the pressure differential that exists due to compressor operation. After the
refrigerant flows past an isolation valve, an in-line filter drier, and a sight glass/moisture indicator, it is directed
over the motor by spray nozzles. The refrigerant collects in the bottom of the motor casing and is then drained
back into the cooler through the motor refrigerant drain line. The motor is protected by temperature thermistors
embedded in the stator windings. An increase in motor winding temperature past the motor override set point
overrides the temperature capacity control to hold, and if the motor temperature exceeds 5.5°C above this set
point, the controls close the inlet guide vanes. If the temperature rises above 50°C, the compressor shuts down.
See Fig. 7.
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