Carrier 19XRV Start-Up, Operation And Maintenance Instructions Manual page 80

COOLER CONDENSER PRESSURE TRANSDUCER
AND OPTIONAL WATERSIDE FLOW DEVICE CALI-
BRATION -- Calibration can be checked by compming the
plessme leadings from file transducer to an accurate refrigera-
tion gage leading. These readings can be viewed or calibrated
from the HEAT_EX screen on the ICVC. The transducer can
be checked grad calibrated fit 2 pressure points. These calibra-
tion points me 0 psig (0 kPa) and between 25 and 250 psig
(173 and 1724 kPa). To calibrate these transducers:
1. Shut down the compressor, coolek and condenser pumps.
NOTE: There should be no flow through the heat
exchangers.
2. Disconnect the transducer in question from its Schmder
fitting for cooler or condenser transducer calibration. For
oil pressure or flow device calibration keep transducer in
place.
NOTE: If the cooler or condenser vessels are at
0 psig (0 kPa) or are open to atmospheric pressure, the
transducers can be calibrated for zero without remov-
ing the transducer from the vessel.
3. Access the HEAT_EX scleen 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 WATER
DELTA P and CONDENSER WATER DELTA P on the
HEAT_EX screen, and OIL PUMP 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 ptuameter 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 or
flow devices.
If the transducer value is not within the calibration
range, the transducer returns to the original reading. If
the pressure 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 by the TRANSDUCER VOLTAGE REF
supply voltage signal (displayed in CONTROL TEST
menu in the PRESSURE TRANSDUCERS screen) or
measure across the positive (+ red) and negative
(- black) leads of the transducer. For example, the
condenser transducer voltage reference is measured
fit CCM terminals J2-4 and J2-6, the condenser trans-
ducer voltage input. The input 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 fdso 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
nitrogen cylinder). The high pressure point can be
calibrated by accessing the appropriate transducer pmam-
eter on the HEAT_EX screen, highlighting the pm'ametek
pressing the _ softkey, and then using the
[INCREASE 1 or [DECREASE] softkeys to adjust the
vfdue to the exact pressure on the refrigerant gage. Press
the _ softkey to finish the calibration. Pressures fit
high altitude locations must be compensated fok 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 compressor oil discharge pressure transducer and
the oil sump pressure transducer will offset an adverse trans-
ducer tolerance stack up and allow the calibration to proceed.
TRANSDUCER REPLACEMENT -- Since the transducers
are mounted on Schrader-type fittings, there is no need to
remove refrigerant from the vessel when replacing the trans-
ducers. Disconnect the transducer winng. Do not pull on the
transducer wires. Unscrew the transducer from the Schmder
fitting. When instfdling 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 refi'igerant leaks.
Be sure to use a back-up wrench on the Schrader fitting
whenever removing a transducek since the Schmder fitting
may back out with the transducek causing an uncontrolled
loss of refrigerant and possible injury to personnel.
Control Algorithms Checkout Procedure -- One
of the tables on the [CVC SERVICE menu is CONTROL
ALGORITHM STATUS. The maintenance screens may be
viewed from the CONTROL ALGORITHM STATUS table to
see how a particulm control algorithm is operating.
These maintenance screens are very useful in helping to
determine how the control temperature is calculated and guide
vane positioned and also for observing the leactions from load
changes, control point overrides, hot gas bypass, surge preven-
tion, etc. The tables are:
Table 15- Control Algorithm Status Tables
TABLE EXPANDED DESCRIPTION
NAME
CAPACITY Capacity This tableshows all values used to
Control calculate the chilled water/brine
control point.
OVERRIDE Override Details of all chilled water control
Status override values.
LL MAINT LEAD/LAG Indicates LEAD/LAG operation
Status status.
OCCDEFCM Time The Local and CCN occupied
Schedules schedules are displayed here to
Status help the operator quickly deter-
mine whether the schedule is in
the "occupied" mode or not.
WSMDEFME Water The water system manager is a
System CCN module that can turn on the
Manager chiller and change the chilled water
Status control point, This screen indicates
the status of this system.
VFD HIST VFD Alarm Displays VFD values at last fault.
History
LOADSHED Loadshed DisplaysLeadshed (Demand Limit)
Status status.
CURALARM Current Displays current chiller alarms.
Alarm Status
Surge and hot gas bypass parameters may be observed in
the HEAT_EX screen. The surge and hot gas bypass control
algorithm status is viewed from tiffs screen. All values defiling
wifll this control are displayed.
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