Shutdown Sequence; Automatic Soft Stop Amps Threshold; Chilled Water Recycle Mode - Carrier 19XRV Start-Up, Operation And Maintenance Instructions Manual

MACHINE SAFETIES,
EVAPORATOR PUMP
CONDENSER
WATER PUMP
WATER FLOW, CHILLED
WATER TEMP, GUIDE VANES
OIL PUMP,TOWER FAN CONTROL
OIL PRESSURE
COMPRESSOR,
COMPRESSOR ONTIME,
SERVICE ONTIME
15-MINUTE
START*TO-START
1-MINUTE
STOP-TO-START
*'TIME
ODE
3OM-
_RESSC
tUNNIN
I !
II
F G O/A
A -- START INITIATED: Pre-start checks are made; evaporator pump
started,
B -- Condenser water pump started (5 seconds after A),
C -- Water flows verified (30 seconds to 5 minutes maximum after B).
Chilled water temperatures checked against control point, Guide
vanes checked for closure, Oil pump started; tower fan control
enabled.
D -- Oil pressure verified (15 seconds minimum, 300 seconds maximum
after C).
E -- Compressor motor starts; compressor ontime and service ontime
start, 15-minute inhibit timer starts (10 seconds after D), total com-
pressor starts advances by one, and the number of starts over a
12-hour period advances by one.
F -- SHUTDOWN INITIATED -- Compressor motor stops; compressor
ontime and service ontime stop, and 1-minute inhibit timer starts.
G -- Oil pump and evaporator pumps deenergized (60 seconds after F).
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 minutes
after E; minimum of 1 minute after F).
Fig. 27 -- Control Sequence
Shutdown
Sequence--Chiller
shutdown begins if
any of the following occurs:
• the STOP button is pressed for at least one second (the
alarm light blinks once to confirm the stop command)
• a recycle condition is present (see Chilled W_tter Recycle
Mode section)
• the time schedule has gone into unoccupied mode
• the chiller protective limit has been reached and chiller is
in alarm
• the start/stop status is overridden to stop from the CCN
network or the [CVC
When a stop signfd occurs, the shutdown sequence first
stops the compressor by deactivating the VFD output to the
motor A status message of "SHUTDOWN IN PROGRESS,
COMPRESSOR DEENERGIZED" is displayed, and the
comptessor ontime and service ontime stop. The guide vanes
are then brought to the closed position. The oil pump relay and
the chilled water/brine pump telay shut down 60 seconds after
the compressor stops. The condenser water pump shuts down
at the same time if the ENTERING CONDENSER WATER
temperature is greater than or equal to 115 F (46.1 C) find
the CONDENSER REFRIG TEMP is greater titan the
CONDENSER FREEZE POINT plus 5 F (-15.0 C). The
stop-to-statl timer now begins to count down. If the
statl-to-stmt timer value is still greater than the value of the
start-to-stop timet: then this time displays on the ICVC.
Certain conditions that occur during shutdown can change
this sequence.
• [f the AVERAGE LINE CURRENT is greater than 5%
alter shutdown, the oil pump and chilled water pump
remain energized and the alarm is displayed.
• The condenser pump shuts down when the CON-
DENSER PRESSURE is less than the COND PRESS
OVERRIDE threshold minus 3.5 psi (24.1 kPa) and the
CONDENSER REFRIG TEMP is less than or equal to the
ENTERING CONDENSER WATER temperature plus
3° F (-1.6° C).
• If the chiller shuts down due to low refl'igerant tempera-
ture, the chilled water pump continues to run until the
LEAVING (/HILLED WATER temperature is greater than
the CONTROL POINTtemperature, plus 5° F (2.8 ° C).
Automatic Soft Stop Amps Threshold -- The soft
stop fillips threshold feature closes the guide vanes of the
compressor automaticfflly if a non-recycle, non-alarm stop
signal occurs before the compressor motor is deenergized.
Any time the compressor is directed to STOP (except in the
cases of a fault or recycle shutdown), the guide vanes ate
directed to close, and the compressor shuts off when any of the
following is true:
• AVERAGE LINE CURRENT (%) drops below the
SOFT STOP AMPS THRESHOLD
• ACTUAL GUIDE VANE POSITION drops below 4%
• 4 minutes have elapsed
• the STOP button is pressed twice
If file chiller enters an alarm state or if the compressor enters
a RECYCLE mode, the compressor deenergizes immediately.
To activate the soft stop amps threshold feature, scroll to the
bottom of OPTIONS screen on the [CVC. Use the
[INCREASE] or [DECREASE[ softkey to set the SOFT STOP
AMPS THRESHOLD parmneter to the percent of amps at
which the motor will shut down. The default setting is 100%
alnps (no soft stop). The range is 40 to 100%.
When the soft stop amps threshold feature is being applied,
a status message, "SHUTDOWN IN PROGRESS, COM-
PRESSOR UNLOADING" displays on the ICVC.
The soft stop amps threshold function can be terminated and
the compressor motor deenergized immediately by depressing
the STOP button twice.
Chilled Water Recycle Mode-- The chiller may
cycle off and wait until the load increases to restart when the
compressor is running in a lightly loaded condition. This
cycling is norlnal and is known as "recycle." A recycle shut-
down is initiated when any of the following conditions are true:
• LEA1/ING CHILLED WATER temperature (or ENTER-
ING CHILLED WATER temperature, if the ECW
CONTROL OPTION is enabled) is more than 5 ° F
(2.8 ° C) below the CONTROL POINT.
•
LEAI/ING CHILLED WATER temperature (or ENTER-
ING CHILLED WATER temperature, if the ECW
CONTROL OPTION is enabled) is below the CONTROL
POINT. and the chilled water temperature difference is
less than the (RECYCLE CONTROL) SHUTDOWN
DELTA T (configured in the EQUIPMENT SERVICE/
SETUPI table).
• the LEA1/ING (/HILLED WATER temperature is within
3 ° F (1.7 ° C) of the EI/AP REFRIG TRIPPOINT.
NOTE: Recycle shutdown will not occur if the CONTROL
POINT has been modified (e.g., by a chilled water reset input)
within the previous 5 minutes of operation.
Also, chilled water recycle logic does not apply to Ice Build
operation (refer to page 46).
When the chiller is in RECYCLE mode, the chilled water
pump relay remains energized so the chilled water temperatute
can be monitored for increasing load. The recycle control uses
RESTART DELTA T to check when the compressor should be
restarted. This is an opettltor-configured function which
defaults to 5 ° F (2.8 ° C). This value can be viewed or modified
51