Specifications

16
OIL HEATER CONTACTOR (1C) — This contactor is lo-
cated in the power panel (Fig. 12) and operates the heater at ei-
ther 115 or 230 v. It is controlled by the PIC II to maintain oil
temperature during chiller shutdown. Some 19XR chillers
shipped in 2002 were equipped with oil heaters powered by
line voltage. Refer to the control panel wiring schematic.
OIL PUMP CONTACTOR (2C) — This contactor is located
in the power panel. It operates all 200 to 575-v oil pumps.
The PIC II energizes the contactor to turn on the oil pump as
necessary.
HOT GAS BYPASS CONTACTOR RELAY (3C)
(Optional) — This relay, located in the power panel, controls
the opening of the hot gas bypass valve. The PIC II energizes
the relay during low load, high lift conditions.
CONTROL TRANSFORMERS (T1, T2) — These transform-
ers convert incoming control voltage to 24 vac power for the 3
power panel contactor relays, CCM, and ICVC.
SENSORS — Three types of temperature sensors are used.
Figure 13 shows a typical temperature sensor for which
sensor wells are not used, in systems having an ICVC control-
ler. For this type, the sensor cable can be easily disconnected
from the sensor, which is in direct contact with the fluid.
The other typical temperature sensor has sensor wells. See
Fig. 14. For this type, the sensor cable cannot be separated
from the sensor itself, but the sensor can be easily removed
from the well without breaking into the fluid boundry.
The third type of temperature sensor is a thermistor, which
is installed either in the motor windings or at the thrust bearing
within the compressor. Both of these have redundant sensors
such that if one fails, the other can be connected external to the
machine. See Table 2 for a list of standard instrumentation sen-
sors.
The PIC II control determines refrigerant temperature in the
condenser and evaporator from pressure in those vessels, read
from the corresponding pressure transducers. See Fig. 14. The
pressure values are converted to the equivalent saturation tem-
peratures for R-134a refrigerant. When the chiller is running, if
the computed value for EVAPORATOR REFRIG TEMP is
greater than, or within 0.6° F (0.33° C) of the LEAVING
CHILLED WATER temperature, its value is displayed as 0.6° F
(0.33° C) below LEAVING CHILLED WATER temperature.
When the chiller is running, if the computed value for CON-
DENSER REFRIG TEMP is less than, or within 1.2° F
(0.67° C) of the LEAVING COND WATER temperature, its val-
ue is displayed as 1.2° F (0.67° C) above LEAVING COND
WATER temperature.
A Refrigerant Saturation Temperature sensor (thermistor) is
located in the base of the evaporator, sensing refrigerant tem-
perature directly. Evaporator and condenser water side differ-
ential pressure transducers are not standard and are not re-
quired. The ICVC software uses the evaporator saturation re-
frigerant temperature in place of differential pressure flow
detection to provide evaporator freeze protection.
Approach temperatures are shown in the HEAT_EX screen.
EVAPORATOR APPROACH is defined as LEAVING
CHILLED WATER TEMPERATURE minus EVAPORATOR
REFRIGERANT TEMP (from the transducer). CONDENS-
ER APPROACH is defined as CONDENSER REFRIGER-
ANT TEMP (derived from condenser pressure) minus LEAV-
ING CONDENSER WATER temperature. When the chiller is
running, the displayed value for either approach will not be less
than 0.2° F (0.1° C). If either approach value exceeds the value
configured in the SETUP1 screen, the corresponding Approach
Alert message will be entered into the ALERT HISTORY
table.
Fig. 13 — Control Sensors (Temperature)
OIL HEATER CONDUIT
CONTROL PANEL
POWER CONDUIT
OPTIONAL HOT GAS
BYPASS CONDUIT
3C HOT GAS BYPASS
RELAY (OPTIONAL)
T2-24 VAC POWER TRANSFORMER
FOR ICVC AND CCM
T1-24 VAC POWER TRANSFORMER
FOR HOT GAS BYPASS RELAY,
OIL PUMP CONTACTOR, AND
OIL HEATER CONTACTOR
T1
T2
OIL HEATER
CONTACTOR
11 12 13
21 22 23
11 12 13
21 22 23
3
1
6
5
4
2
51
50
43
17
C
B
A
OIL PUMP
CONTACTOR
Fig. 12 — Power Panel
a19-1856