Ice Build Control — The ice build control option auto- matically sets the CONTROL POINT of the chiller to a temper- ature 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. 17 and 18 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 SERVICE table. From there, select the OPTIONS screen to enable or disable the ICE BUILD OPTION. See Table 2, Example 17.
•The ICE BUILD SETPOINT can be configured from the SETPOINT display, which is accessed from the PIC II main menu. See Table 2, Example 9.
•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. 19 and the section on Time Schedule Operation, page 20, 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 ter- minate the ice build cycle. The ice build cycle can be config- ured to terminate if:
•the ENTERING CHILLED WATER temperature is less than the ICE BUILD SETPOINT. In this case, the opera- tor 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 chilled water temperature is less than the ice build set point and the remote contact inputs from an ice level indicator 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).
•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 CVC/ICVC by an operator, changed from another CCN device, or changed by other algo- rithms 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 oper- ation 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.
•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 (dis- able), 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 compres- sor restarts and controls the chilled water/brine tempera- ture 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
•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 — Compressor operation terminates, based on temperature, if the ICE BUILD TERMINATION parameter is set to 0 (TEMP), the ENTERING CHILLED WATER temperature is less than the ICE BUILD SETPOINT, and the ICE BUILD RECYCLE is set to DSABLE. If the ICE BUILD RECY- CLE OPTION is set to ENABLE, a recycle shutdown oc- curs and recycle
3.Remote Contacts/Ice Level Input — Compressor opera- tion terminates when the ICE BUILD TERMINATION parameter is set to 1 (CONTACTS) and the remote con- tacts 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
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