Trane RTWA 70-125 TON - Manual (Page 6)

6 RLC-SVD03A-EN
General Information
High Pressure Cutout Switch
Low Pressure Cutout Switch
Variable Speed Fan Drive
Motor Temperature Thermostats
Slide Valve Load/Unload Solenoids
Step Load Solenoid Valve
Chiller Module (CPM) IU1
The CPM module performs machine (chiller) level control and protection
functions. Only one CPM is present in the chiller control system. The CPM
acts as the master controller to the other modules, running top level machine
control algorithms, initiating and controlling all inter-module communication
over the IPC, and providing parameters and operational requests (i.e. loading
and unloading, starting and stopping) to the other modules in the system via
the IPC. The CPM also contains nonvolatile memory, which allows it to
remember configuration and set-up values, setpoints, historical diagnostics
etc. for an indefinite period of time following a power loss. Direct hard wired
I/O associated with the CPM includes low voltage analog inputs, low voltage
binary inputs, 115 VAC binary inputs and 115 VAC (rated) relay outputs. See
Chiller Module (CPM) (1U1) on page 46 for further details.
Compressor Module (MCSP) 1U4 and 1U5
The MCSP module employs the input and output circuits associated with a
particular compressor and refrigeration circuit. Two MCSP modules are used
in the UCM system, one for each compressor. Included are low voltage
analog and digital circuits, 115 VAC input, and 115 VAC output switching
devices. The output switching devices associated with the compressor motor
controlling function are contained in this module. The outputs of this module
control one compressor motor stop/start contactor, one compressor motor
transition contactor, one oil heater, three solenoid valves (compressor load,
compressor unload, step loader), and up to four fan motor contactors or
groups of contactors. Refer to the chiller's line wiring diagrams for details. Dip
switches are provided for redundant programming of the compressor current
overload gains, and for unique IPC address identification during operation.
Inputs to this module include motor temperature thermostats, thermisters,
and safety switches. See
Compressor Module (MCSP) (1U4 AND 1U5) on
page 72 for details.
Expansion Valve Module (EXV) 1U3
The EXV module provides power and control to the stepper motor driving the
electronic expansion valves of the chiller. Each module handles two valves,
one in each refrigeration circuit.
Input to the EXV Module is provided by four temperature sensors (two per
refrigeration circuit). The sensors are located in the respective refrigeration
circuits of the chiller and sense Saturated Evaporator and Suction tempera-
tures and calculate the superheat temperatures. High level operational
commands as well as superheat setpoints are received by the EXV Module
over the IPC from the CPM module to modulate the EXV's.