Cooler; Condenser; Motor-Compressor; Control Center - Carrier 17 Start Up & Operation Manual

Cooler —
This vessel (also known as the evaporator) is
located underneath the condenser, next to the utility vessel.
The cooler is maintained at lower temperature/pressure so
that evaporating refrigerant can remove heat from water flow-
ing through its internal tubes.
Condenser —
The condenser operates at a higher
temperature/pressure than the cooler, and has water flowing
through its internal tubes in order to remove heat from the
refrigerant.
Motor-Compressor —
tem temperature/pressure differences and moves the heat
carrying refrigerant from the cooler to the condenser.
Control Center —
The control center is the user inter-
face for controlling the machine and regulates the machine
capacity as required to maintain proper leaving chilled
water temperature. The control center:
• registers cooler, condenser, and lubricating system
pressures
• shows machine operating condition and alarm shutdown
conditions
• records the total machine operating hours and how many
hours the machine has been running
• sequences machine start, stop, and recycle under micro-
processor control
• provides access to other CCN (Carrier Comfort Network)
devices
Motor Starter (Purchased Separately) —
allows for the proper starting and disconnecting of the elec-
trical energy for the compressor-motor, oil pump, oil heater,
and control panels.
Utility Vessel —
During normal operation, this vessel
functions as an economizer, returning flash gas to the second
stage of the compressor and increasing the efficiency of the
refrigeration cycle. During periods of shutdown and service,
the utility vessel can serve as a storage tank for the
refrigerant.
REFRIGERATION CYCLE (Fig. 4)
The machine compressor continuously draws large quan-
tities of refrigerant vapor from the cooler, at a rate deter-
mined by the amount of guide vane opening. This compres-
sor suction reduces the pressure within the cooler, allowing
the liquid refrigerant to boil vigorously at a fairly low tem-
perature (typically 38 to 42 F [3 to 6 C]).
The liquid refrigerant obtains the energy needed to va-
porize by removing heat from the water or brine in the cooler
tubes. The cold water or brine can then be used in air con-
ditioning and/or other processes.
After removing heat from the water or brine, the refrig-
erant vapor enters the first stage of the compressor, is
compressed and flows into the compressor second stage. Here
it is mixed with flash-economizer gas and is further
compressed.
Compression raises the refrigerant temperature above
that of the water flowing through the condenser tubes.
When the warm (typically 98 to 102 F [37 to 40 C]) refrig-
erant vapor comes into contact with the condenser tubes, the
relatively cool condensing water (typically 85 to 95 F
[29 to 35 C]) removes some of the heat and the vapor con-
denses into a liquid.
This component maintains sys-
The starter
The liquid refrigerant passes through an orifice into the
FLASC chamber. Because the coolest condenser water is flow-
ing through the FLASC, it is at a lower pressure and part of
the entering liquid refrigerant will flash to vapor, thereby cool-
ing the remaining liquid. The vapor is then recondensed by
the condenser water flowing through the FLASC chamber.
The subcooled liquid refrigerant drains into a high-side
valve chamber which meters the refrigerant liquid into a flash
economizer chamber. Pressure in this chamber is interme-
diate between condenser and cooler pressures. At this lower
pressure, some of the liquid refrigerant flashes to gas, fur-
ther cooling the remaining liquid. The flash gas, having ab-
sorbed heat, is returned directly to the compressor second
stage. Here it is mixed with discharge gas that is already com-
pressed by the first-stage impeller. Since the flash gas has to
pass through only half the compression cycle, to reach con-
denser pressure, there is a savings in power.
The cooled liquid refrigerant in the economizer is me-
tered through the low-side valve chamber into the cooler.
Because pressure in the cooler is lower than economizer pres-
sure, some of the liquid flashes and cools the remainder to
evaporator (cooler) temperature. The cycle is now complete.
MOTOR/OIL REFRIGERATION COOLING CYCLE
(19EX CHILLERS)
The motor is cooled by liquid refrigerant taken from the
bottom of the condenser vessel (Fig. 4). Flow of refrigerant
is maintained by the pressure differential that exists due to
compressor operation. After the refrigerant flows past an iso-
lation valve, an in-line filter, and a sight glass/moisture in-
dicator, the flow is split between motor cooling and oil cool-
ing systems.
Flow to the motor moves through an orifice and into the
motor. On models with a solenoid valve, the valve will open
if additional motor cooling is required. 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 then is drained back into the cooler through the motor
refrigerant drain line. 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. On models with a solenoid valve, higher
motor temperatures (above 125 F [51 C]) energize the so-
lenoid to provide additional motor cooling. On all models, a
further increase in temperature past the motor override set
point will override the temperature capacity control to hold,
and if the motor temperature rises 10° F (5.5° C) above this
set point, will close the inlet guide vanes. If the temperature
rises above the safety limit, the compressor will shut down.
On machines with EX compressors and 41-48 cooler sizes,
the oil is also cooled by liquid refrigerant. Refrigerant that
flows to the oil cooling system is regulated by a thermostatic
expansion valve. There is always a minimum flow bypass-
ing the TXV, which flows through an orifice. The TXV valve
regulates flow into the oil/refrigerant plate and frame-type
heat exchanger. The bulb for the expansion valve controls
oil temperature to the bearings. The refrigerant leaving the
heat exchanger then returns to the cooler.
On machines with FA compressors, the oil is water cooled.
Water flow through the oil cooler is manually adjusted by a
plug valve to maintain an operating temperature at the res-
ervoir of approximately 145 F (63 C).
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