Refrigeration Cycle; Motor And Lubricating Oil; Cooling Cycle - Carrier 19XRV Start-Up, Operation And Maintenance Instructions Manual

REFRIGERATION CYCLE
The compressor continuously draws refrigerant vapor from
the cooler at a rate set by the amount of guide vane opening or
compressor speed. As the compressor suction reduces the
pressure in the coolel: the remaining refrigerant boils at a fairly
low temperature (typically 38 to 42 F [3 to 6 C]). Tile energy
required for boiling is obtained from the water flowing through
the cooler tubes. With heat energy removed, the water becomes
cold enough to use in tin air conditioning circuit or for process
liquid cooling.
After taking heat from the water, the refrigerant vapor is
compressed. Compression adds still more heat energy, and the
refrigerant is quite wmm (typic_flly 98 to 102 F [37 to 40 C])
when it is discharged t]om the compressor into the condensel:
Relatively cool (typically 65 to 90 F [18 to 32 C]) water
flowing into the condenser tubes removes heat from the refrig-
erant and the vapor condenses to liquid.
The liquid refi'igerant passes through orifices into the
FLASC (Flash Subcooler) chamber (Fig. 3). Since the FLASC
chamber is at a lower plessure, part of the liquid refrigerant
flashes to vapol: thereby cooling the lemaining liquid. The
FLASC vapor is recondensed on the tubes which are cooled by
entering condenser watel: The liquid drains into a float cham-
ber between the FLASC chamber and cooler Here a float v_dve
forms a liquid seal to keep FLASC chamber vapor from enter-
ing the coolel: When liquid refrigerant passes through the
vMve, some of it flashes to vapor in the reduced pressure on the
cooler side. In flashing, it removes heat from the remaining liq-
uid. The refrigerant is now at a temperature and plessure at
which the cycle began.
MOTOR AND LUBRICATING OIL
COOLING CYCLE
The motor and the lubricating oil are cooled by liquid re-
frigerant taken from the bottom of the condenser vessel
(Fig. 3). Refrigerant flow is maintained by the pressure differ-
ential that exists due to compressor operation. After the refrig-
erant flows past an isolation valve, tin in-line filtel: and a sight
glass/moisture indicatol: the flow is split between the motor
cooling and oil cooling systems.
Flow to the motor cooling system passes through an orifice
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 di'ain line.
An orifice (in the motor shell) maintains a higher pressure in
the motor shell than in the coolel: The motor is protected by a
temperature sensor imbedded in the stator windings. An
increase in motor winding temperature past the motor override
set point overrides the temperatme 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 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/lefrigerant plate and fralne-type heat exchang-
er (the oil cooler in Fig. 3). The expansion valve bulbs control
oil temperature to the bemings. The refrigerant leaving the oil
cooler heat exchanger returns to the chiller coolel:
FLASC CHAMBER
CONDENSER
WATER
Ii
FLOATVAWE.
CHAMBER
DRIER
MOISTURE/
FLOW
INDICATOR
ORIFICE-
FITTING
VFD'
COOLING
ISOLATION
VALVE
THERMOSTATIC
EXPANSION
VALVE
(TXV)
UNIT
MOUNTED
VFD
(VARIABLE
FREQUENCY
DRIVE)
HEAT
EXCHANGER
SOLENOID
VALVE (OPTION)
DIFFUSER
VANE
MOTOR
COOLER ISOLATION
VALVE (OPTION)
Fig. 3 -- Refrigerant Motor Cooling and Oil Cooling Cycles
REFRIGERANT
LIQUID
REFRIGERANT
VAPOR
_ EFRIGERANT
LIQUID/VAPOR
F_ OIL
CHILLED
WATER