18
A Refrigerant Saturation Temperature sensor (thermistor) is
located in the base of the evaporator, sensing refrigerant
temperature directly. Evaporator and condenser water side
differential pressure transducers are not standard and are not
required. The ICVC software uses the evaporator saturation
refrigerant 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 EVAP SATURATION
TEMP (from the temperature sensor). CONDENSER AP-
PROACH is defined as CONDENSER REFRIG TEMP
(derived from condenser pressure) minus LEAVING CON-
DENSER 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 con-
figured in the SETUP1 screen, the corresponding Approach
Alert message will be entered into the Alert History table.
FLOW DETECTION — Flow detection for the evaporator
and condenser is a required condition for start-up and used in
the freeze protection safety. Flow and no flow conditions are
detected from a combination of several measurements. The
usage of waterside differential pressure measurements is not
standard or required.
Positive determination of flow on the evaporator side is
made if the following conditions are true: (1) the EVAP SATU-
RATION TEMP reads higher than 1° F (0.6° C) above the
EVAP REFRIG TRIPPOINT, and (2) EVAP REFRIG TEMP
(determined from the Evaporator Pressure sensor) is greater
than the EVAP REFRIG TRIPPOINT. (If the unit is in Pump-
down or Lockout mode, conditions (1) and (2) are not required
to establish flow.) On the condenser side, positive determina-
tion of flow is made if the following conditions are true: (1) the
CONDENSER PRESSURE is less than 165 psig (1139 kPa),
and (2) CONDENSER PRESSURE is less than the configured
COND PRESS OVERRIDE threshold by more than 5 psi
(34.5 kPa). In addition, if the waterside differential pressure
measurement option is enabled, the waterside pressure differ-
entials (cooler and condenser) must exceed their respective
configured cutout thresholds.
A No Flow determination is made on the evaporator side if
(1) the EVAP SATURATION TEMP reads lower than 1° F
(0.6° C) below the EVAP REFRIG TRIPPOINT, or (2) EVAP
REFRIG TEMP (determined from the Evaporator Pressure
sensor) is less than the EVAP REFRIG TRIPPOINT and the
EVAPORATOR APPROACH exceeds the configured EVAP
APPROACH ALERT threshold. On the condenser side, a
No Flow determination is also made if the CONDENSER
APPROACH exceeds the configured COND APPROACH
ALERT threshold and either (1) CONDENSER PRESSURE
exceeds 165 psig (1139 kPa) or (2) CONDENSER PRES-
SURE exceeds the configured COND PRESS OVERRIDE
threshold by more than 5 psi (34.5 kPa). In addition, if the
water side differential pressure measurement option is enabled,
a differential below the configured EVAP or COND FLOW
DELTA P CUTOUT value is sufficient to establish No Flow in
either heat exchanger.
If No Flow (for either cooler or condenser) has been deter-
mined, and subsequently conditions change such that neither
conditions for Flow nor No Flow are all satisfied, the determi-
nation will remain No Flow.
In the standard ICVC setup, waterside differential pressure
indication is disabled by default. The displays for CHILLED
WATER DELTA P and CONDENSER WATER DELTA P in
the HEAT_EX screen will show “*****”. In order to enable
the option and display a value, change FLOW DELTA P
DISPLAY to ENABLE in the SETUP1 screen. Pairs of pres-
sure transducers may be connected to the CCM at terminals
J3 13-24 in place of the standard resistors and jumpers to deter-
mine water-side pressure differentials as in the standard ICVC
configuration. (NOTE: If the FLOW DELTA P DISPLAY is
enabled, but the standard CCM connection is retained, a differ-
ential value of approximately 28.5 psi (197 kPa) will always be
displayed.)
If waterside differential pressure transducers are used, flow
is detected from differential pressure between sensors (pressure
transducers) located in water inlet and outlet nozzles, for each
heat exchanger. The thresholds for flow determination (EVAP
FLOW DELTA P CUTOUT, COND FLOW DELTA P CUT-
OUT) are configured in the SETUP1 screen. If the measured
differential is less than the corresponding cutout value for
5 seconds, the determination is that flow is absent. If no flow is
detected after WATER FLOW VERIFY TIME (configured in
the SETUP1 screen) after the pump is commanded to start by
the PIC, a shutdown will result, and the corresponding loss-of-
flow alarm (alarm state 229 or 230) will be declared. If the
measured differential exceeds the Flow Delta P cutout value,
flow is considered to be present.
Alternatively, normally open flow switches may be used for
flow indication. In this case, install an evaporator side flow
switch in parallel with a 4.3k ohm resistor between CCM
terminals J3 17-18, replacing the jumper. See page 120. For a
condenser side flow switch do the same between CCM termi-
nals J3 23-24. If this type of flow switch circuit is used, it is
important to perform a zero point calibration (with the flow
switch open).
SHRINK WRAP
STRAIN RELIEF
1/8” NPT
THERMOWELL
REMOVABLE
TEMPERATURE
SENSOR
Fig. 12 — Temperature Sensor Used
With Thermal Well
Fig. 13 — Control Sensors
(Pressure Transducers, Typical)
a23-1624
a19-957
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