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4. A high pressure point can also be calibrated between
25 and 250 psig (172.4 and 1723.7 kPa) by attaching a
regulated 250 psig (1724 kPa) pressure (usually from a
nitrogen cylinder). The high pressure point can be cali-
brated by accessing the appropriate transducer parame-
ter on the HEAT_EX screen, highlighting the
parameter, pressing the
using the
INCREASE
adjust the value to the exact pressure on the refrigerant
gage. Press the
ENTER
tion. Pressures at high altitude locations must be com-
pensated for, so the chiller temperature/pressure
relationship is correct.
The PIC II does not allow calibration if the transducer is too
far out of calibration. In this case, a new transducer must be in-
stalled and re-calibrated.
TRANSDUCER REPLACEMENT — Since the transducers
are mounted on Schrader-type fittings, there is no need to re-
move refrigerant from the vessel when replacing the transduc-
ers. Disconnect the transducer wiring by pulling up on the
locking tab while pulling up on the weather-tight connecting
plug from the end of the transducer. Do not pull on the trans-
ducer 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.
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.
softkey, and then
SELECT
or
softkeys to
DECREASE
softkey to finish the calibra-
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 particular control algorithm is operating.
These maintenance screens are very useful in helping to de-
termine how the control temperature is calculated and guide
vane positioned and for observing the reactions from load
changes, control point overrides, hot gas bypass, surge preven-
tion, etc. The tables are:
CAPACITY
Capacity
Control
OVERRIDE
Override
Status
HEAT_EX
Surge/HGBP
Status
LL_MAINT
LEAD/LAG
Status
OCCDEFCM
Time
Schedules
Status
WSMDEFME
Water
System
Manager
Status
Control Test —
The Control Test feature can check all the
thermistor temperature sensors, pressure transducers, pumps
and their associated flow devices, the slide valve, and other
control outputs such as hot gas bypass. The tests can help to de-
termine whether a switch is defective or a pump relay is not op-
erating, as well as other useful troubleshooting issues. During
pumpdown operations, the pumps are energized to prevent
freeze-up and the vessel pressures and temperatures are dis-
played. The Pumpdown/Lockout feature prevents compressor
start-up when there is no refrigerant in the chiller or if the ves-
sels are isolated. The Terminate Lockout feature ends the
Pumpdown/Lockout after the pumpdown procedure is reversed
and refrigerant is added.
LEGEND TO TABLES 9A-9J
— Chiller Control Module
CM
CCN — Carrier Comfort Network
CVC — Chiller Visual Controller
CHW — Chilled Water
ISM
— Integrated Starter Module
PIC II — Product Integrated Control II
VFD — Variable Frequency Drive
78
This table shows all values
used to calculate the chilled
water/brine control point.
Details of all chilled water con-
trol override values.
The surge and hot gas bypass
control algorithm status is
viewed from this screen. All
values dealing with this control
are displayed.
Indicates LEAD/LAG opera-
tion status.
The Local and CCN occupied
schedules are displayed here
to help the operator quickly
determine whether the sched-
ule 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.
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