Specifications

9
The oil pump suction is fed from the oil reservoir. An oil
pressure relief valve maintains 18 to 25 psid (124 to 172 kPad)
differential pressure in the system at the pump discharge. For
compressors equipped with rolling element bearings, a range of
18 to 40 psid (124 to 172 kPad) is normal. This differential
pressure can be read directly from the ICVC default screen.
The oil pump discharges oil to the oil filter assembly. This filter
can be closed to permit removal of the filter without draining
the entire oil system (see Maintenance sections, pages 95-99,
for details). The oil is then piped to the oil cooler heat exchang-
er. The oil cooler uses refrigerant from the condenser as the
coolant. The refrigerant cools the oil to a temperature between
120 and 140 F (49 to 60 C).
As the oil leaves the oil cooler, it passes the oil pressure
transducer and the thermal bulb for the refrigerant expansion
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 or on the bearing race if the compressor is equipped
with rolling element bearings. The oil then drains into the oil
reservoir at the base of the compressor. The PIC II (Product In-
tegrated Control II) measures the temperature of the oil in the
sump and maintains the temperature during shutdown (see Oil
Sump Temperature and Pump Control section, page 49). This
temperature is read on the ICVC default screen.
During the chiller start-up, the PIC II energizes the oil pump
and provides 45 seconds of pre-lubrication to the bearings after
pressure is verified before starting the compressor. During
shutdown, the oil pump will run for 30 seconds to post-
lubricate after the compressor shuts down. The oil pump can
also be energized for testing purposes during a Control Test. If
the controls are subjected to a power failure, then the controls
will energize the pump for 30 seconds every 30 minutes until
the chiller is started.
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 re-
frigerant in the oil to flash. The resulting oil foam cannot be
pumped efficiently; therefore, oil pressure falls off and lubrica-
tion is poor. If oil pressure falls below 15 psid (103 kPad) dif-
ferential, the PIC II will shut down the compressor.
When the oil pump is not running and the oil heater remains
energized for 30 minutes, the oil pump will be started and will
run for 30 seconds to evenly distribute the heat in the oil
system.
There are three pump-filter configurations. The original
vane pump, in which the oil filter is contained in the pump
housing, followed by the vane pump with the oil filter being
external in the oil piping between the oil pump and the oil cool-
er. The third configuration is the gerotor pump, also with the
external oil filter.
A gerotor pump has two rotors, one is inside the other and
their center points are offset with respect to each other. This
type of pump provides a smooth continuous flow. It is also qui-
eter than other designs.
The gerotor pump can be most easily identified by the exter-
nal location of the oil pressure regulator. The regulator is locat-
ed on the bottom of the pump pointing horizontally to the left.
See Fig. 5.
Bearings — The 19XR compressor assemblies include
four radial bearings and four thrust bearings. The low speed
shaft assembly is supported by two journal bearings located
between the motor rotor and the bull gear. The bearing closer to
the rotor includes a babbitted thrust face which opposes the
normal axial forces which tend to pull the assembly towards
the transmission. The bearing closer to the bull gear includes a
smaller babbitted thrust face, designed to handle counterthrust
forces.
For compressors equipped with hydrodynamic bearings, the
high speed shaft assembly is supported by two journal bearings
located at the transmission end and mid-span, behind the laby-
rinth seal. The transmission side of the midspan bearing also
contains a tilting shoe type thrust bearing which opposes the
main axial forces tending to pull the impeller towards the suc-
tion end. The impeller side face of the midspan bearing in-
cludes a babbitted thrust face, designed to handle counterthrust
forces.
For compressors equipped with rolling element bearings,
the high speed shaft assembly has been redesigned to utilize
rolling element bearings (radial and thrust). Machines employ-
ing the rolling element bearings can be expected to have higher
oil pressure and thrust bearing temperatures than those com-
pressors using the alternate bearing design.
Oil Reclaim System — The oil reclaim system returns
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 recov-
ered by skimming it from the operating refrigerant level in the
cooler vessel.
PRIMARY OIL RECOVERY MODE — Oil is normally re-
covered 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 discharge gas
pressure to power an eductor, the oil is drawn from the housing
and is discharged into the oil reservoir.
SECONDARY OIL RECOVERY METHOD — The sec-
ondary method of oil recovery is significant under light load
conditions, when the refrigerant going up to the compressor
suction does not have enough velocity to bring oil along. Under
these conditions, oil collects in a greater concentration 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 be-
hind to be collected by the primary oil recovery method.
STARTING EQUIPMENT
The 19XR chiller requires a motor starter to operate the cen-
trifugal hermetic compressor motor, the oil pump, and various
auxiliary equipment. The starter is the main field wiring inter-
face for the contractor.
See Carrier Specification Z-415 for specific starter require-
ments, Z-416 for free-standing VFD requirements and Z-417
for unit-mounted VFD requirements. All starters must meet
these specifications in order to properly start and satisfy me-
chanical safety requirements. Starters may be supplied as sepa-
rate, free-standing units or may be mounted directly on the
chiller (unit mounted) for low voltage units only.
Typically three separate circuit breakers are inside the start-
er. This includes (1) the main compressor motor circuit breaker,
(2) a circuit breaker which provides power to chiller controls
and the oil heater (provided at 115 vac), and (3) a circuit break-
er which provides power at line voltage to the oil pump. The
latter two are typically wired in parallel with the first so that
power is provided to those services when the main breaker is
open. The disconnect switch on the starter front cover is con-
nected to the main breaker.