Load Balancing; Auto. Restart After Power Failure; Ice Build Control; Ice Build Initiation - Carrier 19XR Start-Up, Operation And Maintenance Instructions Manual

LOAD BALANCING — When the LOAD BALANCE
OPTION (see LEADLAG screen) is enabled, the lead chiller
sets the ACTIVE DEMAND LIMIT in the lag chiller to the
lead chiller's compressor motor load value MOTOR PER-
CENT KILOWATTS or AVERAGE LINE CURRENT on the
MAINSTAT screen). This value has limits of 40% to 100%.
When the lag chiller ACTIVE DEMAND LIMIT is set, the
CONTROL POINT must be modified to a value of 3° F
(1.67° C) less than the lead chiller's CONTROL POINT value.
If the LOAD BALANCE OPTION is disabled, the ACTIVE
DEMAND LIMIT and the CONTROL POINT are forced to
the same value as the lead chiller.
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 II 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 start-
ing simultaneously helps reduce the inrush demands on the
building power system.
Ice Build Control —
automatically sets the CONTROL POINT of the chiller to a
temperature that allows ice building for thermal storage.
NOTE: For ice build control to operate properly, the PIC II
must be in CCN mode.
NOTE: See Fig. 15 and 16 for more information on ice build-
related menus.
The PIC II can be configured for ice build operation.
• From the SERVICE menu, access the EQUIPMENT SERV-
ICE table. From there, select the OPTIONS screen to en-
able or disable the ICE BUILD OPTION. See
Table 2, Example 16.
• The ICE BUILD SETPOINT can be configured from the
SETPOINT display, which is accessed from the PIC II main
menu. See Table 2, Example 8.
• The ice build schedule can be viewed or modified from
the SCHEDULE table. From this table, select the ice build
schedule (OCCPC02S) screen. See Fig. 17 and the section
on Time Schedule Operation, page 19, for more informa-
tion 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 sched-
ules, 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, ac-
cessed 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 if:
• 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 on the
OPTIONS screen.
• the REMOTE CONTACT inputs from an ice level indi-
cator are opened. In this case, the operator sets the ICE
BUILD TERMINATION parameter to 1 on the OPTIONS
screen.
The ice build control option
• the chilled water temperature is less than the ice build set
point and the remote contact inputs from an ice level in-
dicator are open. In this case, the operator sets the ICE
BUILD TERMINATION parameter to 2 on the OPTIONS
screen.
• the end of the ice build time schedule has been reached.
ICE BUILD INITIATION — The ice build time schedule
(OCCPC02S) is the means for activating the ice build
option. The ice build option 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).
1. CHILLER START/STOP is forced to START.
2. The CONTROL POINT is forced to the ICE BUILD
SETPOINT.
3. 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 CVC by an operator, changed
from another CCN device, or changed by other algorithms
in the PIC II control system.
NOTE: Items 1-3 (shown above) 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.
START-UP/RECYCLE OPERATION — If the chiller is not
running when ice build activates, the PIC II checks the fol-
lowing conditions, based on the ICE BUILD TERMINA-
TION value, to avoid starting the compressor unnecessarily:
• if ICE BUILD TERMINATION is set to the TEMP option
and the ENTERING CHILLED WATER temperature is less
than or equal to the ICE BUILD SETPOINT;
• if ICE BUILD TERMINATION is set to the CONTACTS
option and the remote contacts are open;
• if the ICE BUILD TERMINATION is set to the BOTH (tem-
perature and contacts) option and the ENTERING CHILLED
WATER temperature is less than or equal to the ICE BUILD
SETPOINT and the remote contacts are open.
The ICE BUILD RECYCLE on the OPTIONS screen de-
termines whether or not the chiller will go into an ice build
RECYCLE mode.
• If the ICE BUILD RECYCLE is set to DSABLE (disable),
the PIC II reverts to normal temperature control when the
ice build function terminates.
• If the ICE BUILD RECYCLE is set to ENABLE, the
PIC II goes into an ICE BUILD RECYCLE mode and the
chilled water pump relay remains energized to keep the
chilled water flowing when the ice build function termi-
nates. If the temperature of the ENTERING CHILLED
WATER increases above the ICE BUILD SETPOINT plus
the RECYCLE RESTART DELTA T value, the compressor
restarts and controls the chilled water/brine temperature to
the ICE BUILD SETPOINT.
TEMPERATURE CONTROL DURING ICE BUILD — Dur-
ing ice build, the capacity control algorithm shall use the
CONTROL POINT minus 5 F (−2.8 C) for control of the
LEAVING CHILLED WATER temperature. See Table 2, ex-
ample 9, the CAPACITY CONTROL parameter on the CA-
PACITY screen.) The ECW CONTROL OPTION and any
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