Chilled Water Recycle Mode - Carrier 19XRV Start-Up, Operation And Maintenance Instructions Manual

If the chiller enters an alarm state or if the compressor
enters a RECYCLE mode, the compressor deenergises
immediately.
To activate the soft stop amps threshold feature, scroll to
the bottom of OPTIONS screen on the ICVC. Use the
InCReASe or DeCReASe softkey to set the SOFT STOP
AMPS THRESHOLD parameter to the percent of amps
at which the motor will shut down. The default setting is
100% amps (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,
COMPRESSOR UNLOADING" displays on the ICVC.
The soft stop amps threshold function can be terminated
and the compressor motor deenergised immediately by
pressing the STOP button twice.

6.3 - 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 normal and is known as
"recycle." A recycle shutdown is initiated when any of the
following conditions are true:
• LEAVING CHILLED WATER temperature (or
ENTERING CHILLED WATER temperature, if the
ECW CONTROL OPTION is enabled) is more than
.8 K below the CONTROL POINT.
• LEAVING CHILLED WATER temperature (or
ENTERING 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 EQUIP-
MENT SERVICE/SETUP1 table).
• the LEAVING CHILLED WATER temperature is
within 1.7 K of the EVAP 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 47).
When the chiller is in RECYCLE mode, the chilled water
pump relay remains energised so the chilled water tempe-
rature can be monitored for increasing load. The recycle
control uses RESTART DELTA T to check when the com-
pressor should be restarted. This is an operator-configured
function which defaults to .8 K. This value can be viewed
or modified on the SETUP1 table. The compressor will
restart when the chiller is:
• in LCW CONTROL and the LEAVING CHILLED
WATER temperature is greater than the CONTROL
POINT plus the (RECYCLE CONTROL) RESTART
DELTA T.
• in ECW CONTROL and the ENTERING CHILLED
WATER temperature is greater than the CONTROL
POINT plus the (RECYCLE CONTROL) RESTART
DELTA T.
Once these conditions are met, the compressor initiates a
start-up with a normal start-up sequence.
An alert condition may be generated if 5 or more recycle
start-ups occur in less than 4 hours. Excessive recycling can
reduce chiller life; therefore, compressor recycling due to
extremely low loads should be reduced.
To reduce compressor recycling, use the time schedule to
shut the chiller down during known low load operation
period, or increase the chiller load by running the fan systems.
If the hot gas bypass is installed, adjust the values to ensure
that hot gas is energised during light load conditions.
Increase the (RECYCLE CONTROL) RESTART DELTA
T on the SETUP1 table to lengthen the time between
restarts.
The chiller should not be operated below design minimum
load without a hot gas bypass installed.
6.3.1 - Safety shutdown
A safety shutdown is identical to a manual shutdown with
the exception that, during a safety shutdown, the ICVC
displays the reason for the shutdown, the alarm light blinks
continuously, and the spare alarm contacts are energised.
After a safety shutdown, the ReSet softkey must be pressed
to clear the alarm. If the alarm condition is still present, the
alarm light continues to blink. Once the alarm is cleared,
the operator must press the CCn or LoCAL softkeys to
restart the chiller.
6.3.2 - to prevent accidental start-up
A chiller STOP override setting may be entered to prevent
accidental start-up during service or whenever necessary.
Access the MAINSTAT screen and using the neXt or
pReVIoUS softkeys, highlight the CHILLER START/
STOP parameter. Override the current START value by
pressing the SeLeCt softkey. Press the neXt softkey
followed by the enteR softkey. The word SUPVSR!
displays on the ICVC indicating the override is in place.
To restart the chiller, the STOP override setting must be
removed. Access the MAINSTAT screen and using the
neXt or pReVIoUS softkey highlight CHILLER START/
STOP. The 3 softkeys that appear represent 3 choices:
• StARt - forces the chiller ON
• Stop - forces the chiller OFF
• ReLeASe - puts the chiller under remote or schedule
control
To return the chiller to normal control, press the ReLeASe
softkey followed by the enteR softkey. For more infor-
mation, see Local Start-Up, page 51.
The default ICVC screen message line indicates which
command is in effect.
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