Motor Cooling Cycle; Lubrication Cycle; Summary; Details - Carrier AquaEdge 23XRV Start-Up, Operation And Maintenance Instructions Manual

Fig. 12 — Refrigerant Flow Schematic, P Compressor (With Optional Economizer)

MOTOR COOLING CYCLE

For Q and R compressors, one half of the motor is cooled by suc-
tion gas while the other half is cooled by liquid refrigerant taken
from the bottom of the condenser vessel. The P compressor has
two spray nozzles that cool the motor by injecting liquid refriger-
ant. The flow of liquid refrigerant is maintained by the pressure
differential that exists due to compressor operation. The refriger-
ant flows through an isolation valve, in-line filter/drier, and a sight
glass/moisture indicator (dry-eye), into the motor through the mo-
tor spray nozzle. See Fig. 9-12.
IMPORTANT: To avoid adverse effects on chiller operation,
consideration must be made to condenser water temperature
control. Consult the Chiller Builder for required steady state
operational limits. Inverted start conditions are acceptable for
short durations; generally, for periods exceeding 5 minutes,
special control strategy solutions are to be used to allow the
chiller to build minimum refrigerant pressure differential (and
thereby adequate equipment cooling).
The motor spray nozzle is orificed to control refrigerant flow
through the gaps between the rotor and stator. The refrigerant col-
lects in the bottom of the motor casing and then drains into the
cooler through the motor cooling drain line.
The motor is protected by a temperature sensor and a temperature
switch embedded in the stator windings. If motor thermistor tem-
perature exceeds 197°F (88°C) the override function will start un-
loading the compressor. If the motor winding temperature rises
above the 200°F (93°C) safety limit, the compressor will shut
down.

LUBRICATION CYCLE

Summary

The 23XRV chiller requires an oil pump. Oil flow is provided by a
magnetically coupled, motor-driven oil pump. Oil flows through
the oil filter into the compressor rotors and bearings. The cycle is
referred to as a "low side" oil system. See Fig. 13.

Details

The oil system:
• lubricates the roller bearings which support the male and
female rotors, and the ball bearings of the 23XRV com-
pressor.
• lubricates the male and female rotors.
Oil is charged into the system through a hand valve located on the
bottom of the oil sump. Sight glasses on the oil sump permit oil
level observation. When the compressor is shut down, an oil level
should be visible in the oil sump sight glass. During operation, the
oil level should always be visible in the oil sump sight glass. Ap-
proximately 10 gal. (37.9 L) of oil is charged into the sump.
Oil from the compressor bearing drain is drained directly into the
oil sump. Refrigerant is driven from the oil as it flows around the
oil sump heater and into the strainer housing. The oil pump draws
the oil through a strainer and forces it through an oil filter.
The filter housing is capable of being isolated by upstream and
downstream valves to permit filter replacement. An oil pressure
regulator valve directs excessive oil back into the oil sump. Oil
supplied to the compressor is monitored by an oil pressure sensor.
The Oil Delta P value is equal to the difference between the oil
pressure leaving the filter and the oil sump pressure. It is read di-
rectly from the PIC6 home screen.
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