Ice Build Control - Carrier 19XRV Start-Up, Operation And Maintenance Instructions Manual

4. Lag chiller temperature pulldown rate (TEMP PULL-
DOWN DEG/MIN) of the chilled water temperature
is less than 0.7 K per minute.
5. The standby chiller is not running as a lag chiller.
6. The configured LAG START TIMER configured in the
lag (acting lead) chiller has elapsed. The LAG START
TIMER is started when the lag (acting lead) chiller's
ramp loading is completed.
5.27.7 - Load balancing
When the LOAD BALANCE OPTION (see LEADLAG
screen) is enabled, the lead chiller sets the ACTIVE DE-
MAND LIMIT in the lag chiller to the lead chiller's com-
pressor motor load value MOTOR PERCENT KILOWATTS
or AVERAGE LINE CURRENT on the MAINSTAT
screen). This value has limits of 40% to 100%. In addition,
the CONTROL POINT for the lag chiller must be modified
to a value of 1.67 K less than the lead chiller's CONTROL
POINT value. If the LOAD BALANCE OPTION is dis-
abled, the ACTIVE DEMAND LIMIT and the CONTROL
POINT are both forced to the same value as the lead chiller.
5.27.8 - Auto. Restart after power failure
When an auto. restart condition occurs, each chiller may
have a delay added to the start-up sequence, depending on
its lead/lag configuration. The lead chiller does not have a
delay. The lag chiller has a 45-second delay. The standby
chiller has a 90-second delay. The delay time is added after
the chiller water flow is verified. The PIC III ensures the
guide vanes are closed. After the guide vane position is
confirmed, the delay for lag and standby chillers occurs
prior to energizing the oil pump. The normal start-up
sequence then continues. The auto. restart delay sequence
occurs whether the chiller is in CCN or LOCAL mode and
is intended to stagger the compressor motor starts.
Preventing the motors from starting simultaneously helps
reduce the inrush demands on the building power system.

5.28 - Ice build control

The selectable ice build mode permits use of the chiller to
refreeze or control the temperature of an ice reservoir which
may, for example, be used for thermal storage. This mode
differs from water or brine chilling in that termination
(indication that the need for cooling has been satisfied) is
based on input(s) other than the temperature which is
being controlled during operation.
NOTE: For ice build control to operate properly, the PIC
III must be in CCN mode.
The PIC III can be configured for ice build operation.
• From the SERVICE menu, access the EQUIPMENT
SERVICE table. From there, select the OPTIONS
screen to enable or disable the ICE BUILD OPTION.
See Table 3, Example 17.
• The ICE BUILD SETPOINT can be configured from
the SETPOINT display, which is accessed from the
PIC III main menu. See Table 3, Example 9.
• The ice build schedule can be viewed or modified from
the SCHEDULE table. From this table, select the ice
build schedule (OCCPC0S) screen. See Fig. 8 and the
section on Time Schedule Operation, page 19, for more
information on modifying chiller schedules.
The ice build time schedule defines the period(s) during
which ice build is active if the ice build option is enabled.
If the ice build time schedule overlaps other schedules, the
ice build time schedule takes priority. During the ice build
period, the CONTROL POINT is set to the ICE BUILD
SETPOINT for temperature control. The ICE BUILD
RECYCLE and ICE BUILD TERMINATION parameters,
accessed from the OPTIONS screen, allow the chiller
operator to recycle or terminate the ice build cycle. The ice
build cycle can be configured to terminate when:
• the ENTERING CHILLED WATER temperature is
less than the ICE BUILD SETPOINT. In this case,
the operator sets the ICE BUILD TERMINATION
parameter to 0 (the default setting) on the OPTIONS
screen.
• the ICE BUILD CONTACTS input from an ice level
indicator are opened. In this case, the operator sets
the ICE BUILD TERMINATION parameter to 1 on
the OPTIONS screen.
• the chilled water temperature is less than the ICE
BUILD SETPOINT and the ICE BUILD CONTACTS
input from an ice level indicator are open. In this case,
the operator sets the ICE BUILD TERMINATION
parameter to  on the OPTIONS screen.
• the end of the ice build time schedule (OCCPC0S)
has been reached.
5.28.1 - Ice build initiation
The ice build time schedule (OCCPC0S) is the means for
activating the ice build option. Ice Build is enabled if:
• a day of the week and a time period on the ice build
time schedule are enabled. The SCHEDULE screen
shows an X in the day field and ON/OFF times are
designated for the day(s),
• and the ICE BUILD OPTION is enabled.
The following events take place (unless overridden by a
higher authority CCN device).
• CHILLER START/STOP is forced to START.
• The CONTROL POINT is forced to the ICE BUILD
SETPOINT.
• Any force (Auto) is removed from the ACTIVE
DEMAND LIMIT.
note: A parameter's value can be forced, that is, the value
can be manually changed at the ICVC by an operator,
changed from another CCN device, or changed by other
algorithms in the PIC III control system.
note: The Ice Build steps do not occur if the chiller is
configured and operating as a lag or standby chiller for
lead/lag operation and is actively being controlled by a lead
chiller. The lead chiller communicates the ICE BUILD
SET POINT, the desired CHILLER START/STOP state,
and the ACTIVE DEMAND LIMIT to the lag or standby
chiller as required for ice build, if configured to do so.
5.28.2 - Start-up/recycle operation
If the chiller is not running when ice build activates, the
PIC III checks the following conditions, based on the ICE
BUILD TERMINATION value, to avoid starting the
compressor unnecessarily:
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