In the LOCAL/ENABLE position, the chiller is under lo- cal control and responds to the scheduling configuration and set point data input at its own local interface device (key- pad and display module).
In the CCN position, the chiller is under remote control and responds only to CCN network commands. The occupied/ unoccupied conditions are defined by the network. All key- pad and display functions can be read at the chiller regard- less of position of the switch.
CCN run or stop condition is established by a command from the CCN network. It is not possible to force outputs from the CCN network, except that an emergency stop com- mand shuts down the chiller immediately and causes ‘ ‘ALARM 52” to be displayed.
Table 2 - LOCAL/ENABLE-STOP-CCN
Switch Positions and Operation
S W I T C H |
| I | U N I T |
| CONFIGURATION AND | |
|
| SET POINT CONTROL | ||||
P O S I T I O N |
| OPERATION |
|
|
| |
| Keypad Control 1CCN Control | |||||
|
|
|
|
| ||
|
|
|
|
|
|
|
STOP | I Unit | Cannot | Run | Read/Write | 1 Read Only | |
LOCAL/ENABLE |
| Unit | Can Run |
| Read/Limited Write | Read Only |
|
| Unit Cannot Run | Read Only | ReadlWrite | ||
CCN :t2 1 |
| Unit | Can Run |
| Read Onlv | Read/Limited Write |
|
|
|
|
|
|
|
Electronic Expansion Valve (EXV) - The micro- processor controls the EXV through the EXV driver mod- ule. Inside the expansion valve is a linear actuator stepper motor.
The lead compressor in each circuit has a thermistor and a pressure transducer located in the suction manifold after the compressor motor. The thermistor measures the tem- perature of the superheated gas entering the compressor cyl- inders. The pressure transducer measures the refrigerant pressure in the suction manifold. The microprocessor con- verts the pressure reading to a saturated temperature. The difference between the temperature of the superheated gas and the saturation temperature is the superheat. The micro- processor controls the position of the electronic expansion valve stepper motor to maintain 29 F (16 C) superheat.
At initial unit
Sensors - The Flotronic TM 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 - Thermistor and Transducer Locations
|
| THERMISTORS |
Sensor |
| Location |
Cooler Leaving Water Temp
T:Cooler Entering Water Temp Compressor Suction Gas Temp Circuit A
| Ti | Compressor Suction Gas Temp Circuit B | ||
| TIO | Remote Temperature Sensor (Accessory) | ||
|
| PFIESSURETRANSDUCERS | ||
| Sensor |
|
| Location |
| DPT - A | Compressor | Al | Discharge Pressure |
| SPT - A | Compressor Al | ||
| OPT - A | Compressor | Al | Oil Pressure |
| Compressor | Bl | Discharge Pressure | |
| SPT - B | Compressor | Bi | Suction Pressure |
| OPT - B | Compressor | Bl | Oil Pressure |
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|
|
Compressor Protection Control Module (CPCS)
- Each compressor on models 30GN070 (50 Hz), 080- 100, and 240B, 270B, has its own CPCS as standard equip- ment. All
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 protec- tion. Ground current protection is accomplished by using a CGF (compressor ground fault) board in conjunction with the CR. The CGF 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 signal contacts, it will lock the compressor off by deener- gizing the proper
A
PROTECTION BOARD
Fig. 2 - Compressor Protection Control Module
4