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14 - MAJOR SYSTEM COMPONENTS AND
OPERATION DATA
14.1 - Geared twin screw compressor
• 30HXC and 30GX units use 06N geared twin screw
compressors
• 06NA are used on 30GX (air-cooled condensing application)
• 06NW are used on 30HXC (water-cooled condensing
application)
• Nominal capacities range from 39 to 80 tons. Economized or
non economized models are used depending on the 30HXC
and 30GX unit size.
14.1.1 - Oil Filter
The 06N screw compressor has an oil filter integral in the
compressor housing. This filter is field replaceable.
14.1.2. - Refrigerant
The 06N screw compressor is specially designed to be used in
R134 a system only.
14.1.3 - Lubricant
The 06N screw compressor is approved for use with the
following lubrifiant.
CARRIER MATERIAL SPEC PP 47-32
14.1.4 - Oil Supply Solenoid Valve
An oil supply solenoid valve is standard on the compressor to
isolate the compressor from oil flow when the compressor is
not operating.
The oil solenoid is field replaceable.
14.1.5 - Suction & Economizer Screens
To increase the reliability of the compressor, a screen has been
incorporated as a standard feature into suction and economizer
inlets of the compressor.
14.1.6 - Unloading System
The 06N screw compressor has an unloading system that is
standard on all compressors. This unloading system consists of
two steps of unloading that decrease the compressor capacity
by rerouting partially compressed gas back to suction.
14.2 - Evaporator
30HXC and 30GX chillers use a flooded evaporator. The water
circulates in the tubes and the refrigerant is on the outside in
the shell. One vessel is used to serve both refrigerant circuits.
There is a center tube sheet which separates the two refrigerant
circuits. The tubes are 3/4" diameter copper with an enhanced
surface inside and out. There is just one water circuit, and
depending on the size of the chiller, there may be two or three
water passes. A cooler liquid level sensor provides optimized
flow control.
At the top of the cooler are the two suction pipes, one in each
circuit. Each has a flange welded to it, and the compressor
mounts on the flange.
14.3 - Condenser and oil separator (30HXC)
30HXC chiller use a vessel that is a combination condenser
and oil separator. It is mounted below the cooler. Discharge gas
leaves the compressor and flows through an external muffler to
the oil separator, which is the upper portion of the vessel. It
enters the top of the separator where oil is removed, and then
flows to the bottom portion of the vessel, where gas is
condensed and subcooled. One vessel is used to serve both
refrigerant circuits. There is a center tube sheet which separates
the two refrigerant circuits. The tubes are 3/4" or 1" diameter
copper with enhanced surface inside and out. There is just one
water circuit with two water passes.
14.4 - Oil separator (30GX)
In the air-cooled units, the oil separator is a pressure vessel that
is mounted under the outside vertical condenser coils.
Discharge gas enters at the top of the separator where much of
the oil separates and drains to the bottom. The gas then flows
through a wire mesh screen where the remaining oil is
separated and drains to the bottom.
14.5 - Electronic Expansion Device (EXD)
The microprocessor controls the EXD through the EXV control
module. The EXD will either be an EXV or an Economizer.
Inside both these devices is a linear actuator stepper motor.
High-pressure liquid refrigerant enters the valve through the
bottom. A series of calibrated slots are located inside the orifice
assembly. As refrigerant passes through the orifice, the pres-
sure drops and the refrigerant changes to a 2-phase condition
(liquid and vapor). To control refrigerant flow for different
operating conditions, the sleeve moves up and down over the
orifice, thereby changing effective flow area of expansion
device. The sleeve is moved by a linear stepper motor. The
stepper motor moves in increments and is controlled directly
by the processor module. As the stepper motor rotates, motion
is transferred into linear movement by the lead screw. Through
the stepper motor and lead screws, 1500 discrete steps of
motion are obtained. The large number of steps and long stroke
result in very accurate control of refrigerant flow. Each circuit
has a liquid level sensor mounted vertically into the top of the
cooler shell. The level sensor consists of a small electric
resistance heater and three thermistors wired in series
positioned at different heights inside the body of the well. The
heater is designed so that the thermistors will read
approximately 93.3°C in dry air. As the refrigerant level rises
in the cooler, the resistance of the closest thermistor(s) will
greatly change. This large resistance difference allows the
control to accurately maintain a specified level. The level
sensor monitors the refrigerant liquid level in the cooler and
sends this information to the PSIO-1. At initial start-up, the
EXV position is at zero. After that, the microprocessor keeps
accurate track of the valve position in order to use this infor-
mation as input for the other control functions. It does this by
initializing the EXV’s at startup. The processor sends out
enough closing pulses to the valve to move it from fully open
to fully closed, then resets the position counter to zero. From
this point on, until the initialization, the processor counts the
total number of open and closed steps it has sent to each valve.
14.6 - Economizer
Economizers are installed on 30HXC 190, 285 and 375 and
30GX 182, 267 and 358.
The economizer improves both the chiller capacity and
efficiency as well as providing compressor motor cooling.
Inside the economizer are both a linear EXV stepper motor and
a float valve. The EXV is controlled by the PIC to maintain the
Summary of Contents for 30GX Series
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