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14
Control sequence
To start — Local start-up (manual start-up) is initiated by
pressing the LOCAL or CCN menu softkey, which is indi-
cated on the default international chiller visual control
(ICVC) screen. Time schedule 01 or 03, respectively, must
be in the Occupied mode and the internal 15-minute start-
to-start and the 1-minute stop-to-start inhibit timers must
have expired. All pre-start safeties are checked to verify
that all prestart alerts and safeties are within limits (if one is
not, an indication of the fault displays and the start will be
delayed or is aborted). The signal is sent to start the cooler
liquid pump. Five seconds later, the condenser liquid pump
is energized. If satisfied, it checks the chilled liquid temper-
ature against the control point. If the temperature is less
than or equal to the chilled liquid control point, the con-
denser liquid pump is deenergized and the chiller goes into
a recycle mode.
If the chilled liquid temperature is high enough, the start-
up sequence continues. The oil pump is started and waits a
minimum of 45 sec to verify oil flow. Once oil flow is veri-
fied, the VFD is energized. The control will monitor for a
phase reversal condition. At this time, the following occurs:
• The “start-to-stop” timer is activated.
• The “compressor on-time” and “service on-time” timers
are activated.
• The “starts in 12-hour counter” advances by one.
• The “total compressor starts counter” advances by one.
Once started — If the VFD average current >5% within
15 seconds after VFD start, the machine enters run mode
and speed will be ramped up to meet VFD target speed.
Once the target speed is met the controls, enter the capac-
ity control mode.
Shutdown sequence — The chiller shutdown is initiated
if any of the following occur:
• The Stop button is pressed for at least one second (the
alarm light blinks once to confirm the stop command).
• A recycle shutdown is initiated.
• The time schedule has gone into unoccupied mode.
• The chiller protective limit has been reached and the
chiller is in alarm.
• The start/stop status is overridden to stop from the
ICVC, CCN system, or building management system.
Once the controls shutdown sequence is initiated, the
compressor is stopped and the VFD target speed is set to 0.
If optional soft stop unloading is activated when the Stop
button is pressed or the remote contacts open, motor
speed decreases to a configured amperage level, and the
compressor is stopped. The display indicates “Shutdown in
Progress” while the motor speed decreases. Compressor
ontime and service ontime timers stop once the current in
all phases is <5%, indicating a VFD Stop Complete. The oil
pump and cooler liquid pump are then deenergized. The
condenser liquid pump shuts down when the refrigerant
temperature or entering condenser liquid temperature is be-
low pre-established limits. The 3-minute start-to-stop timer
starts.
Restart — Restart is permitted after both inhibit timers
have expired. If shutdown was due to a safety shutdown,
the reset button must be depressed before restarting the
chiller.
Controls (cont)
MACHINE SAFETIES,
EVAPORATOR PUMP
CONDENSER WATER
PUMP
WATER FLOWS
CHILLED WATER
TEMP,
CONTROL
OIL PUMP
OIL PRESSURE
VERIFIED
VDF FAULT TEST
COMPRESSOR, PHASE
REVERSAL,
COMPRESSOR AND
SERVICE ONTIME
1-MINUTE
STOP-TO-START
TIMER (SOFTWARE
VERSION 13)
15-MINUTE
START-TO-START
TIMER
RAMP VDF TO
TARGET SPEED
COMPRESSOR
RUNNING
A
B
C
D
E
F
G
H
IJ
K
L
O/A
TIME
TOWER FAN
0 0
CONTROL SEQUENCE
0—Phase reversal monitored
A—START INITIATED: Pre-start checks are made; evaporator pump
started
B—Condenser liquid pump started (5 seconds after A); tower fan control
enabled
C—Liquid flows verified (30 sec to 5 minutes maximum after B)
D—Chilled liquid temperature checked against control point; oil pump
on.
E—Oil pressure verified (oil pressure verified 45-300 sec after D).
F—VFD starts; phase reversal conditions monitored; compressor
ontime and service ontime start; 15-minute inhibit timer starts (VFD
fault tests for 15 sec after F)
G—Verify average current >5% within 15 sec after VFD start, ramp to
VFD target speed.
H—Compressor reaches target speed, chiller set to running status
I—Shutdown initiated: Target VFD speed to 0% (or J occurs)
J—Ramp down until percent line current <
soft stop amps threshold
(0-60 sec after I)
K—Oil pump relay off (1-20 sec after J)
L—Evaporator pump deenergized (60 sec after K); condenser pump
and tower fan control may continue to operate if condenser pressure
is high; evaporator pump may continue if in RECYCLE mode
O/A — Restart permitted (both inhibit timers expired) (minimum of 15 min-
utes after F; minimum of 3 minutes after L)