Specifications

As the oil leaves the oil cooler, it passes the oil pressure
transducer and the thermal bulb for the refrigerant expan-
sion valve on the oil cooler. The oil is then divided. Part of
the oil flows to the thrust bearing, forward pinion bearing,
and gear spray. The rest of the oil lubricates the motor shaft
bearings and the rear pinion bearing. The oil temperature is
measured in the bearing housing as it leaves the thrust and
forward journal bearings. The oil then drains into the oil res-
ervoir at the base of the compressor. The PIC II (Product
Integrated Control II) measures the temperature of the oil in
the sump and maintains the temperature during shutdown
(see Oil Sump Temperature Control section, page 36). This
temperature is read on the CVC default screen.
During the chiller start-up, the PIC II energizes the oil pump
and provides 45 seconds of prelubrication to the bearings
after pressure is verified before starting the compressor.
During shutdown, the oil pump will run for 60 seconds to
post-lubricate after the compressor shuts down. The oil pump
can also be energized for testing purposes during a Control
Test.
Ramp loading can slow the rate of guide vane opening to
minimize oil foaming at start-up. If the guide vanes open
quickly, the sudden drop in suction pressure can cause any
refrigerant in the oil to flash. The resulting oil foam can-
not be pumped efficiently; therefore, oil pressure falls off
and lubrication is poor. If oil pressure falls below 15 psid
(103 kPad) differential, the PIC II will shut down the
compressor.
If the controls are subject to a power failure that lasts more
than 3 hours, the oil pump will be energized periodically when
the power is restored. This helps to eliminate refrigerant that
has migrated to the oil sump during the power failure. The
controls energize the pump for 60 seconds every 30 minutes
until the chiller is started.
Oil Reclaim System — The oil reclaim system re-
turns oil lost from the compressor housing back to the oil
reservoir by recovering the oil from 2 areas on the chiller.
The guide vane housing is the primary area of recovery. Oil
is also recovered by skimming it from the operating refrig-
erant level in the cooler vessel.
PRIMARY OIL RECOVERY MODE — Oil is normally
recovered through the guide vane housing on the chiller. This
is possible because oil is normally entrained with refrigerant
in the chiller. As the compressor pulls the refrigerant up from
the cooler into the guide vane housing to be compressed, the
oil normally drops out at this point and falls to the bottom
of the guide vane housing where it accumulates. Using dis-
charge gas pressure to power an eductor, the oil is drawn
from the housing and is discharged into the oil reservoir.
SECONDARY OIL RECOVERY MODE — The secondary
method of oil recovery is significant under light load con-
ditions, when the refrigerant going up to the compressor suc-
tion does not have enough velocity in which to bring oil along.
Under these conditions, oil collects in a greater concentra-
tion at the top level of the refrigerant in the cooler. This oil
and refrigerant mixture is skimmed from the side of the cooler
and is then drawn up to the guide vane housing. There is a
filter in this line. Because the guide vane housing pressure
is much lower than the cooler pressure, the refrigerant boils
off, leaving the oil behind to be collected by the primary oil
recovery method.
JOURNAL
BEARINGS
REAR PINION
BEARING
SIGHT
GLASSES
STRAINER
CHECK
VALVE
ISOLATION
VALVE
SIGHT
GLASS
FILTER
ISOLATION
VALVE
COOLER
OIL
RECLAIM
LINE
STRAINEREDUCTOR
OIL
CHARGE
VALVE
THERMAL
EXPANSION
VALVE BULB
OIL SUPPLY
PRESSURE
TRANSDUCER
ISOLATION
VALVE
OIL
COOLER
OIL PUMP
AND MOTOR
OIL PRESSURE
RELIEF VALVE
OIL
SUPPLY
LINE
FILTER
ISOLATION
VALVE
FILTER
OIL DRAIN
THRUST
THRUST
Fig. 4 — Lubrication System
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