62
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).
• CHILLER START/STOP is forced to START.
• The CONTROL POINT is forced to the ICE BUILD SET-
POINT.
• 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 II control system.
NOTE: The Ice Build steps do not occur if the chiller is config-
ured 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 follow-
ing conditions, based on the ICE BUILD TERMINATION
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
(temperature 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 deter-
mines whether or not the chiller will go into an ice build RE-
CYCLE mode.
• If the ICE BUILD RECYCLE is set to DSABLE (disable),
the PIC II reverts to normal (non-ice build) temperature
control when the ice build function is terminated by satisfy-
ing one of the above conditions. Once ice build is termi-
nated in this manner, it will not be reinitiated until the next
ice build schedule period begins.
• 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 compressor shuts down. If the tem-
perature of the LEAVING CHILLED WATER later increases
above the ICE BUILD SETPOINT plus half the RECYCLE
RESTART DELTA T value, the compressor restarts, con-
trolling the chilled water/brine temperature to the ICE
BUILD SETPOINT.
TEMPERATURE CONTROL DURING ICE BUILD —
During 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. The ECW CON-
TROL OPTION and any temperature reset option shall be ig-
nored, if enabled, during ice build. Also, the following control
options will be ignored during ice build operation:
• ECW CONTROL OPTION and any temperature reset
options (configured on TEMP_CTL screen).
• 20 mA DEMAND LIMIT OPT (configured on
RAMP_DEM screen).
TERMINATION OF ICE BUILD — The ice build function
terminates under the following conditions:
1. Time Schedule — When the current time on the ice build
time schedule (OCCPC02S) is not set as an ice build time
period.
2. Entering Chilled Water Temperature — Ice build opera-
tion terminates, based on temperature, if the ICE BUILD
TERMINATION parameter is set to 0 (TEMP), the EN-
TERING CHILLED WATER temperature is less than the
ICE BUILD SETPOINT, and the ICE BUILD RECYCLE
is set to DSABLE. If the ICE BUILD RECYCLE OP-
TION is set to ENABLE, a recycle shutdown occurs and
recycle start-up depends on the LEAVING CHILLED
WATER temperature being greater than the water/brine
CONTROL POINT plus the RESTART DELTA T
temperature.
3. Remote Contacts/Ice Level Input — Ice build operation
terminates when the ICE BUILD TERMINATION param-
eter is set to 1 (CONTACTS) and the ice build contacts
are open and the ICE BUILD RECYCLE is set to
DSABLE (0). In this case, the contacts provide ice level
termination control. The contacts are used to stop the ice
build function when a time period on the ice build sched-
ule (OCCPC02S) is set for ice build operation. The re-
mote contacts can still be opened and closed to start and
stop the chiller when a specific time period on the ice
build schedule is not set for ice build.
4. Entering Chilled Water Temperature and ICE BUILD
Contacts — Compressor operation terminates when the
ICE BUILD TERMINATION parameter is set to 2
(BOTH) and the conditions described above in items 2
and 3 for entering chilled water temperature and remote
contacts have occurred.
NOTE: It is not possible to override the CHILLER START/
STOP, CONTROL POINT, and ACTIVE DEMAND LIMIT
variables from CCN devices (with a priority 4 or greater)
during the ice build period. However, a CCN device can over-
ride these settings during 2-chiller lead/lag operation.
RETURN TO NON-ICE BUILD OPERATIONS — The
ice build function forces the chiller to start, even if all other
schedules indicate that the chiller should stop. When the ice
build function terminates, the chiller returns to normal tem-
perature control and start/stop schedule operation. The
CHILLER START/STOP
and CONTROL POINT return to nor-
mal operation. If the CHILLER START/STOP or CONTROL
POINT has been forced (with a device of less than 4 priority)
before the ice build function started, when the ice build func-
tion ends, the previous forces (of less than 4 priority) are not
automatically restored.
Attach to Network Device Control — The Service
menu includes the ATTACH TO NETWORK DEVICE
screen. From this screen, the operator can:
• enter the time schedule number (if changed) for
OCCPC03S, as defined in the NET_OPT screen
• attach the ICVC to any CCN device, if the chiller has
been connected to a CCN network. This may include
other PIC-controlled chillers.
• upgrade software
Figure 29 shows the ATTACH TO NETWORK DEVICE
screen. The LOCAL parameter is always the ICVC module ad-
dress of the chiller on which it is mounted. Whenever the con-
troller identification of the ICVC changes, the change is re-
flected automatically in the BUS and ADDRESS columns for
the local device. See Fig. 21. Default address for local device is
BUS 0 ADDRESS 1.
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