Control Algorithms Checkout Procedure; Control Test - Carrier 19XRV Start-Up, Operation And Maintenance Instructions Manual

7.4.2 - transducer replacement
Since the 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. 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.
WARNING: 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
an uncontrolled loss of refrigerant and possible injury to
personnel.

7.5 - Control algorithms checkout procedure

One of the tables on the ICVC SERVICE menu is CON-
TROL 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 show different tables that are
very useful in helping to determine how the control tempe-
rature is calculated and guide vane positioned and also for
observing the reactions from load changes, control point
overrides, hot gas bypass, surge prevention, etc. See Table 9.
Table 9 — Control algorithm status tables
TABLE EXPANDED NAME
CAPACITY Capacity Control
OVERRIDE Override Status
LL_MAINT LEAD/LAG Status
OCCDEFCM Time Schedules
Status
WSMDEFME Water System
Manager
Status
VFD_HIST VFD Alarm History
LOADSHED Loadshed Status
CUR_ALARM Current Alarm Status
HEAT_EX* Surge and HGBP
Status
* The HEAT_EX screen is under the STATUS menu.
56
DESCRIPTION
This table shows all values used to
calculate the chilled water/brine control
point.
Details of all chilled water control
override values.
Indicates LEAD/LAG operation 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.
The water system manager is a CCN
module that can turn on the chiller and
change the chilled water control point.
This screen indicates the status of this
system.
Displays VFD values at last fault.
Displays Loadshed (Demand Limit)
status.
Displays current chiller alarms.
The surge and hot gas bypass control
algorithm status is viewed from this
screen. All values related to this control
are displayed.

7.6 - Control test

The Control Test feature can check all the thermistor
temperature sensors, pressure transducers, pumps and
their associated flow devices, the guide vane actuator, and
other control outputs such as tower fans, VFD cooling
solenoid, shunt trip relay, oil heaters, alarm relay, and hot
gas bypass. The tests can help to determine whether a switch
is defective or a pump relay is not operating, as well as
other useful troubleshooting issues. During pumpdown
operations, the pumps are energised to prevent freeze-up
and the vessel pressures and temperatures are displayed.
The Pumpdown/Lockout feature prevents compressor
start-up when there is no refrigerant in the chiller or if the
vessels are isolated. The Terminate Lockout feature ends
the Pumpdown/Lockout after the pumpdown procedure is
reversed and refrigerant is added.