Specifications

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3. Access the HEAT_EX screen and view the particular
transducer reading (the EVAPORATOR PRESSURE or
CONDENSER PRESSURE parameter on the HEAT_EX
screen). To calibrate oil pressure or liquidside flow
device, view the particular reading (CHILLED LIQUID
DELTA P and CONDENSER LIQUID DELTA P on the
HEAT_EX screen, and OIL PRESSURE DELTA P on the
COMPRESS screen). It should read 0 psi (0 kPa). If the
reading is not 0 psi (0 kPa), but within ± 5 psi (35 kPa),
the value may be set to zero by pressing the
softkey while the appropriate transducer parameter is
highlighted on the ICVC screen. Then press the
softkey. The value will now go to zero. No high end
calibration is necessary for OIL PRESSURE DELTA P,
optional CHILLED LIQUID DELTA P or CON-
DENSER LIQUID DELTA P or for flow devices.
If the transducer value is not within the calibration range,
the transducer returns to the original reading. If the pres-
sure is within the allowed range (noted above), check the
voltage ratio of the transducer. To obtain the voltage ratio,
divide the voltage (dc) input from the transducer (white
wire to black wire) by the TRANSDUCER VOLTAGE
REF supply voltage signal (displayed in CONTROL
TEST menu in the PRESSURE TRANSDUCERS
screen). The TRANSDUCER VOLTAGE REF can be
measured across the positive (+ red) and negative
(– black) leads of the transducer. For example, the con-
denser transducer reference voltage is measured at CCM
terminals J2-4 (black) and J2-6 (red). The condenser
transducer input voltage is measured at CCM terminals
J2-4 (black) and J2-5 (clear or white). The input voltage
to reference voltage ratio must be between 0.80 and 0.11
for the software to allow calibration. Pressurize the
transducer until the ratio is within range, then attempt
calibration again.
4. A high pressure point can also be calibrated between 25
and 250 psig (172.4 and 1723.7 kPa) by attaching a regu-
lated 250 psig (1724 kPa) pressure (usually from a nitro-
gen cylinder). The high pressure point can be calibrated
by accessing the appropriate transducer parameter on the
HEAT_EX screen, highlighting the parameter, pressing
the softkey, and then using the
or softkeys to adjust the value to the exact
pressure on the refrigerant gage. Press the
softkey to finish the calibration. Pressures at high
altitude locations must be compensated for, so the chiller
temperature/pressure relationship is correct.
The PIC III does not allow calibration if the transducer is
too far out of calibration. In this case, a new transducer must be
installed and re-calibrated. If calibration problems are encoun-
tered on the OIL PRESSURE DELTA P channel, sometimes
swapping the oil pressure leaving filter and the oil sump
pressure transducer locations will offset an adverse transducer
tolerance stack up and allow the calibration to proceed.
TRANSDUCER REPLACEMENT — Since the pressure
transducers are mounted on Schrader-type fittings, there is no
need to remove refrigerant from the vessel when replacing the
transducers. Disconnect the transducer wiring by pulling up on
the locking tab while pulling up on the weather-tight connect-
ing plug from the end of the transducer. Do not pull on the
transducer wires. Unscrew the transducer from the Schrader
fitting. When installing a new transducer, do not use pipe sealer
(which can plug the sensor). Put the plug connector back on the
sensor and snap into place. Check for refrigerant leaks.
Control Algorithms Checkout Procedure —
One of the tables on the ICVC SERVICE menu is CONTROL
ALGORITHM STATUS. The maintenance screens may be
viewed from the CONTROL ALGORITHM STATUS table to
see how a particular control algorithm is operating.
These maintenance screens are very useful in helping to
determine how the control temperature is calculated and for
observing the reactions from load changes, control point over-
rides, hot gas bypass, surge prevention, etc. See Table 14.
Table 14 — Control Algorithm
Maintenance Screens
*The HEAT_EX screen is under the STATUS menu.
SELECT
ENTER
SELECT
INCREASE
DECREASE
ENTER
CAUTION
Be sure to use a back-up wrench on the Schrader fitting
whenever removing a transducer, since the Schrader fitting
may back out with the transducer, causing a large leak and
possible injury to personnel.
SCREEN TITLE DESCRIPTION
CAPACITY Capacity
Control
This table shows all values
used to calculate the chilled
liquid control point.
OVERRIDE Override
Status
Details of all chilled liquid and
VFD control override values.
LL_MAINT LEAD/LAG
Status
Indicates LEAD/LAG
operation status.
VFD_HIST VFD Alarm
History
Displays VFD values at last
fault.
LOADSHED Loadshed
Status
Displays Loadshed (Demand
Limit) status.
CUR_ALRM Current
Alarm Status
Displays current chiller
alarms.
WSMDEFME Liquid
System
Manager
Status
The liquid system manager is
a CCN module that can turn
on the chiller and change the
chilled liquid control point. This
screen indicates the status of
this system.
OCCDEFCM Time
Schedules
Status
The Local and CCN occupied
schedules are displayed here
to help the operator quickly
determine whether the
schedule is in the “occupied”
mode or not.
HEAT_EX* HGBP
Status
The hot gas bypass control
algorithm status is viewed
from this screen. All values
related to this control are
displayed.