Lead/Lag Control

Note: Lead/lag control is only available on machines with PSIO Software Version 09 or higher. Lead/lag is a control system process that automatically starts and stops a lag or second

chiller in a 2-chiller water system. Refer to Figure 16 and Figure 17 for menu, table, and screen selection information. On machines that have PSIO software with Lead/Lag capability, it is possible to utilize the PIC controls to perform the lead/lag function on 2 machines. A third machine can be added to the lead/lag system as a standby chiller to start up in case the lead or lag chiller in the system has shut down during an alarm condition and additional cooling is required.

Note: Lead/lag configuration is viewed and edited under Lead/Lag in the Equipment Configura- tion table (located in the Service menu). Lead/lag status during machine operation is viewed in the MAINT04 table in the Control Algorithm Status table. See Table 2.

Lead/Lag System Requirements:

all machines must have PSIO software capable of performing the lead/lag function

water pumps MUST be energized from the PIC controls

water flows should be constant

CCN Time Schedules for all machines must be identical

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Carrier PC211 specifications Lead/Lag Control