Lubrication Cycle; Summary; Details; Oil Reclaim System - Carrier 19XR Start-Up, Operation And Maintenance Instructions Manual

Flow to the motor cooling system passes through an ori-
fice and into the motor. Once past the orifice, the refrigerant
is directed over the motor by a spray nozzle. The refrigerant
collects in the bottom of the motor casing and is then drained
back into the cooler through the motor refrigerant drain line.
A back pressure valve or an orifice in this line maintains a
higher pressure in the motor shell than in the cooler/oil sump.
The motor is protected by a temperature sensor imbedded in
the stator windings. An increase in motor winding tempera-
ture past the motor override set point overrides the tempera-
ture capacity control to hold, and if the motor temperature
rises 10° F (5.5° C) above this set point, closes the inlet guide
vanes. If the temperature rises above the safety limit, the com-
pressor shuts down.
Refrigerant that flows to the oil cooling system is regu-
lated by thermostatic expansion valves (TXVs). The TXVs
regulate flow into the oil/refrigerant plate and frame-type heat
exchanger (the oil cooler in Fig. 3). The expansion valve
bulbs control oil temperature to the bearings. The refrigerant
leaving the oil cooler heat exchanger then returns to the chiller
cooler.

LUBRICATION CYCLE

Summary —
The oil pump, oil filter, and oil cooler make
up a package located partially in the transmission casting of
the compressor-motor assembly. The oil is pumped into a
filter assembly to remove foreign particles and is then forced
into an oil cooler heat exchanger where the oil is cooled to
proper operational temperatures. After the oil cooler, part of
the flow is directed to the gears and the high speed shaft
bearings; the remaining flow is directed to the motor shaft
bearings. Oil drains into the transmission oil sump to com-
plete the cycle (Fig. 4).
Details —
Oil is charged into the lubrication system through
a hand valve. Two sight glasses in the oil reservoir permit oil
level observation. Normal oil level is between the middle of
the upper sight glass and the top of the lower sight glass
when the compressor is shut down. The oil level should be
visible in at least one of the 2 sight glasses during operation.
Oil sump temperature is displayed on the CVC (Chiller
Visual Control) default screen. During compressor opera-
tion, the oil sump temperature ranges between 125 to 150 F
(52 to 66 C).
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. This differential pressure can be read directly from
the CVC 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 65 to 69, for details). The
oil is then piped to the oil cooler heat exchanger. 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 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 35). 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 —
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 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 in which to bring oil
along. Under these conditions, oil collects in a greater con-
centration 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 refrig-
erant boils off, leaving the oil behind to be collected by the
primary oil recovery method.

STARTING EQUIPMENT

The 19XR requires a motor starter to operate the centrifu-
gal hermetic compressor motor, the oil pump, and various
auxiliary equipment. The starter is the main field wiring in-
terface for the contractor.
See Carrier Specification Z-415 for specific starter re-
quirements. All starters must meet these specifications in
order to properly start and satisfy mechanical safety require-
ments. Starters may be supplied as separate, free-standing
units or may be mounted directly on the chiller (unit mounted)
for low-voltage units only.
Three separate circuit breakers are inside the starter. Cir-
cuit breaker CB1 is the compressor motor circuit breaker.
The disconnect switch on the starter front cover is connected
to this breaker. Circuit breaker CB1 supplies power to the
compressor motor.
The main circuit breaker (CB1) on the front of the starter
disconnects the main motor current only. Power is still
energized for the other circuits. Two more circuit break-
ers inside the starter must be turned off to disconnect
power to the oil pump, PIC II controls, and oil heater.
8
The oil reclaim system re-