13
Fig. 10 — Chiller Start/Stop Icon
This initiates the PIC5 starting sequence by displaying the
list of operating modes. Press Local On to initiate start-up.
See Fig. 11.
Fig. 11 — Local On
NOTE: Prior to start-up the start-to-start timer and the stop-to-
start timer must have elapsed and all alarms must be cleared
(see Troubleshooting Guide section).
When start-up is initiated the status screen displays the start-
up progress and the Start/Stop icon blinks green.
Once local start-up begins, the PIC5 control system per-
forms a series of prestart tests to verify that all prestart alerts
and safeties are within acceptable limits. Table 2 shows appro-
priate Prestart Alerts/Alarms conditions. If a test is not success-
ful, the start-up is delayed or aborted. If the tests are successful,
the start-up will be in progress and the COMPRESSOR RUN
STATUS shall be “Startup.” The control shall then energize the
chilled water/brine pump relay.
Five seconds later, the condenser pump relay energizes.
Thirty seconds later the PIC5 control system monitors the
chilled water and condenser water flow devices and waits until
the WATER FLOW VERIFY TIME (operator-configured, de-
fault 5 minutes) expires to confirm flow. After flow is verified,
the chilled water temperature is compared to CONTROL
POINT plus 1/2 CHILLED WATER DEADBAND. If the tem-
perature is less than or equal to this value, the PIC5 control sys-
tem turns off the condenser pump relay and goes into a Recycle
mode.
If the water/brine temperature is high enough, the start-up
sequence continues and checks the guide vane position. If the
guide vanes are more than 4% open, the start-up waits until
the PIC5 control system closes the vanes. If the vanes are
closed and the refrigerant pump pressure difference is less
than 2.5 psid (17.2 kPa), the refrigerant pump relay energizes.
The PIC5 control system then waits until the refrigerant pres-
sure (REF PRESS VERIFY TIME, operator-configured, de-
fault of 40 seconds) reaches 12 psid (82.7 kPa). After refrig-
erant pressure is verified, if high side float chamber has ade-
quate liquid level refrigerant pump will be kept ON for 20
seconds for pre-lube; if not, refrigerant pump will be kept ON
pumping refrigerant from evaporator to the high side float
chamber until liquid level is satisfied. Upon pre-lube satisfied
the compressor start relay is energized.
Compressor ontime and service ontime timers start, and the
compressor STARTS IN 12 HOURS counter and the number of
starts over a 12-hour period counter advance by one.
Failure to verify any of the requirements up to this point will
result in the PIC5 control system aborting the start and display-
ing the applicable prestart alert alarm state number near the
bottom of the home screen on the HMI panel. A prestart failure
does not advance the STARTS IN 12 HOURS counter. Any fail-
ure after the 1CR relay has energized results in a safety shut-
down, advances the starts in 12 hours counter by one, and dis-
plays the applicable shutdown status on the display.
The minimum time to complete the entire prestart sequence
is approximately 185 seconds. See Fig. 12 for normal start-up
timing sequence. See Table 2 for a list of prestart checks.
Lubrication Control — For the 19DV system, refriger-
ant is used to lubricate and cool the compressor bearings. The
refrigerant lubrication system includes refrigerant pump pres-
sure transducers, control valves, filters, liquid level switch and
inhibitor reclaim system. See Fig. 13 for the lube assembly
schematic.
When the chiller is powered on, the controller will maintain
liquid level in condenser float chamber. If liquid level is low,
refrigerant will be pumped from cooler to condenser high side
float chamber until the liquid level switch is ON. Once the
operator pushes the start button, the system will go into prestart
check process.
When Refrigerant Pump request is on for pre-lube and the
bearing pressure difference is OK for start, if cooler tempera-
ture plus leaving condenser water temperature is less than 10°F
(-12.2°C), pump refrigerant from Cooler to Condenser until
compressor is ON. Else, if cooler temperature plus leaving
condenser water is equal or larger than 10°F (-12.2°C), pump
refrigerant from condenser to bearing and drain to condenser
until compressor is ON.
During pre-lubrication, if the bearing pressure difference
is less than 8 psid (55.2 kPa) for 8 seconds continuously, the
chiller will shut down. To proceed to start-up, the bearing pres-
sure difference needs to exceed 12 psid (82.7 kPa) during the
pressure verification time. The compressor will run after the
pre-lubrication process. Refrigerant from the high side con-
denser float chamber will be pumped to bearings and will drain
to cooler. When chiller shuts down, the condenser control valve
will be opened and the refrigerant evaporator control valve will
open (3-way valve will connect evaporator to pump suction).
This position allows refrigerant to be pumped from cooler to
condenser high side float chamber. When the chiller is OFF, al-
ways open cooler control valve. During running, if compressor
is ON and the bearing pressure difference is less than 10 psid
(68.9 kPa) for 10 seconds continuously, the chiller will shut
down.
Unit Start/Stop
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