The TXV is set at the factory to maintain approximately 8 to 12° F (4.4 to 6.7° C) suction superheat leaving the cooler by monitoring the proper amount of refrigerant into the cooler. All TXVs are adjustable, but should not be adjusted unless absolutely necessary. When TXV is used, thermistors T7 and T8 are not required.
The TXV is designed to limit the cooler saturated suction temperature to 55 F (12.8 C). This makes it possible for unit to start at high cooler ¯uid temperatures without overload- ing the compressor.
Sensors Ð The Flotronic™ II chiller control system gath- ers information from sensors to control the operation of the chiller. The units use 6 standard pressure transducers and 4 standard thermistors to monitor system pressures and tem- peratures at various points within the chiller. Sensors are listed in Table 3.
Table 3 Ð Thermistor and Transducer Locations
| THERMISTORS |
Sensor | Location |
T1 | Cooler Leaving Fluid Temp |
T2 | Cooler Entering Fluid Temp |
T7 | Compressor Suction Gas Temp Circuit A |
T8 | Compressor Suction Gas Temp Circuit B |
T10 | Remote Temperature Sensor (Accessory) |
| PRESSURE TRANSDUCERS |
Sensor | Location |
Compressor A1 Discharge Pressure | |
Compressor A1 Suction Pressure | |
Compressor A1 Oil Pressure | |
Compressor B1 Discharge Pressure | |
Compressor B1 Suction Pressure | |
Compressor B1 Oil Pressure | |
|
|
Compressor Protection Control Module (CPCS)
ÐEach compressor on models 30GN070 (50 Hz), 080- 110, and
· compressor contactor control · crankcase heater control
· compressor ground current protection
· status communication to processor board ·
The CR provides all of the same functions as the CPCS with the exception of compressor ground current protection. Ground current protection is accomplished by using a CGF (compressor ground fault module) in conjunction with the CR. The CGF (See Fig. 3) provides the same ground fault function as the CPCS for units where the CPCS is not utilized.
One large relay is located on the CPCS board. This relay (or CR) controls the crankcase heater and compressor contactor. The CPCS also provides a set of signal contacts that the microprocessor monitors to determine the operating status of the compressor. If the processor board determines that the compressor is not operating properly through the sig- nal contacts, it will lock the compressor off by deenergizing the proper
Fig. 2 Ð Compressor Protection Control Module
Fig. 3 Ð Compressor Ground Fault Module
ground of any compressor winding exceeds 2.5 amps. If this condition occurs, the CPCS module shuts down the compressor.
A
±7 psig (2936 ± 48 kPa), is wired in series with the CPCS. If this switch opens during operation, the compressor stops and the failure is detected by the processor when the signal contacts open. The compressor is locked off. If the lead com- pressor in either circuit is shut down by the
OPERATION DATA
Capacity Control Ð The control system cycles compressor to give capacity control steps as shown in Tables
The chilled ¯uid temperature set point can be automati- cally reset by the return temperature reset or space and
The operating sequences shown are some of many pos- sible loading sequences for the control of the leaving ¯uid temperature. If a circuit has more unloaders than another, that circuit will always be the lead circuit.
5