Vfd Cooling Cycle; Lubrication Cycle; Summary; Details - Carrier AquaEdge 19XR series Start-Up, Operation And Maintenance Instructions Manual

Flow to the motor cooling system passes through an orifice
and into the motor. Once past the orifice, the refrigerant is di-
rected over the motor by a spray nozzle. The refrigerant col-
lects in the bottom of the motor casing and is then drained back
into the cooler through the motor refrigerant drain line. An ori-
fice (in the motor shell) maintains a higher pressure in the
motor shell than in the cooler. The motor is protected by a tem-
perature sensor imbedded in the stator windings. An increase in
motor winding temperature past the motor override set point
overrides the temperature capacity control to hold, and if the
motor temperature rises 10 F (5.5 C) above this set point, the
Product Integrated Control II (PIC II) controls close the inlet
guide vanes. If the temperature rises above the safety limit, the
compressor shuts down.
Refrigerant that flows to the oil cooling system is regulated
by thermostatic expansion valves (TXVs). The TXVs regulate
flow into the oil/refrigerant plate and frame-type heat exchang-
er (the oil cooler in Fig. 4 and 5). The expansion valve bulbs
control oil temperature to the bearings. The refrigerant leaving
the oil cooler heat exchanger returns to the chiller cooler.

VFD COOLING CYCLE

The unit-mounted variable frequency drive (VFD) typically
has PIC III controls. The only unit-mounted drive available
with PIC II controls is the 575-v input drive.
The 575-v unit-mounted variable frequency drive (VFD) is
cooled in a manner similar to the motor and oil cooling cycle
(Fig. 4 and 5).
If equipped with a unit-mounted VFD, the refrigerant line
that feeds the motor cooling and oil cooler also feeds the heat
exchanger on the unit-mounted VFD. Refrigerant is metered
through an orifice. The refrigerant leaving the heat exchanger
returns to the cooler.

LUBRICATION CYCLE

The oil pump, oil filter, and oil cooler make
Summary —
up a package located partially in the transmission casing of the
compressor-motor assembly. The oil is pumped into a filter as-
sembly to remove foreign particles and is then forced into an
oil cooler heat exchanger where the oil is cooled to proper op-
erational temperatures. After the oil cooler, part of the flow is
directed to the gears and the high speed shaft bearings; the re-
maining flow is directed to the motor shaft bearings. Oil drains
into the transmission oil sump to complete the cycle (Fig. 6 and
7).
Oil is charged into the lubrication system through
Details —
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 tem-
perature is displayed on the ICVC (International Chiller Visual
Controller) default screen. During compressor operation, the
oil sump temperature ranges between 125 and 150 F (52 and
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. 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 93-98,
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 52). This
temperature is read on the ICVC default screen.
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