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

MOTOR COOLING CYCLE

For Q and R compressors, one half of the motor is cooled by
suction gas while the other half is cooled by liquid refrigerant
taken from the bottom of the condenser vessel. The P compres-
sor has two spray nozzles that cool the motor by injecting liq-
uid refrigerant. The flow of liquid refrigerant is maintained by
the pressure differential that exists due to compressor opera-
tion. The refrigerant flows through an isolation valve, in-line
filter/drier, and a sight glass/moisture indicator (dry-eye), into
the motor through the motor spray nozzle. See Fig. 10-13.

IMPORTANT: To avoid adverse effects on chiller oper-
ation, 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 strat-
egy 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 refrig-
erant collects 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. COMP
MOTOR WINDING TEMP temperatures above the COMP
MOTOR TEMP OVERRIDE threshold (see Capacity Override
section, page 48) will override the chilled liquid temperature
capacity control to hold. If the motor temperature rises 10° F
(5.5 C) above this threshold, the compressor will unload. If the
COMP MOTOR WINDING TEMP rises above the 220 F
(104.4 C) safety limit, the compressor will shut down.

LUBRICATION CYCLE

The 23XRV chiller requires an oil pump. Oil
Summary —
flow is provided by a magnetically coupled, motor-driven oil
pump. Oil flows through the oil filter into the compressor ro-
tors and bearings. The cycle is referred to as a "low side" oil
system. See Fig. 14.
The oil system:
Details —
• lubricates the roller bearings which support the male
and female rotors, and the ball bearings of the 23XRV
compressor.
• 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.
1016
During operation, the oil level should always be visible in the
oil sump sight glass. Approximately 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 PRESSURE DELTA P value is equal
to the difference between the oil pressure leaving the filter and
the oil sump pressure. It is read directly from the ICVC (Inter-
national Chiller Visual Controller) default screen.
Oil is supplied to the compressor through two separate
inlets. One inlet leads to the suction bearings, the other leads to
the discharge bearings. Most of the oil drains back into the
sump while a small amount is used to lubricate the rotors.
Rotor lubrication oil leaves the compressor mixed with the
compressed discharge refrigerant vapor.
The oil sump contains temperature and pressure sensors and
an oil heater. (In some cases a two-stage heater is supplied,
with 500 W for the first stage and 1000 W for the second
stage.) The oil sump is vented to the compressor suction to
minimize the amount of refrigerant absorbed by the oil. The
OIL SUMP TEMPERATURE is measured and displayed on the
ICVC default screen and the COMPRESS screen. The oil
sump pressure is used to calculate the OIL PRESSURE DELTA
P value.
Operating OIL PRESSURE DELTA P must be at least
18 psid (124 kPa) after the OIL PRESS VERIFY TIME has
elapsed. Under normal full load conditions, oil pressure is
typically 20 to 28 psid (138 to 193 kPa). If sufficient oil pres-
sure is not established or maintained the chiller will shut down.
An oil pressure delta P sensor fault will be declared if the OIL
PRESSURE DELTA P is not less than 4 psid (27.6 kPa) prior to
start-up.
If the oil pressure falls below the values specified in Table 1
during start-up, the PIC III control will shut down the chiller.
Table 1 — Oil Pressure Requirements
TIME
(SEC)
BEFORE OIL PUMP ON
AFTER OIL PRESS VERIFY
TIME
DURING START/RUN
16
MINIMUM START-UP OIL
PRESSURE REQUIREMENT
HFC-134A
PSID KPA
< 4 27.6
18 124
15 103