If the address assignments placed into the LAG ADDRESS and STANDBY ADDRESS
values conflic t, the lead/lag will be disa bled and an alert (!) me ssage will o ccur. For exa mple, if
the LAG ADDRESS matches the lead machine’s address, the lead/lag will be disabled and an
alert (!) message will occur. The lead/lag maintenance screen (MAINT04) will display the
message ‘INVALID CONF IG’ in the LEAD/LAG CO NFIGURATION and CURRE N T MODE
fields.
The lead chiller respond s to normal start/st op c on trols such as occupan cy schedule, forc ed
start/stop, and remot e start contact input s . After completing star t up and ramp loading, th e PIC
evaluates the need for additio nal capacity. I f additional c apacity is nee ded, the PIC initiates the
start up of the chiller configured at the LAG ADDRESS. If the lag chiller is faulted (in alarm) or is
in the OFF or LOCAL modes, then the chiller at the STANDBY ADDRESS (if configured) is
requested to start . After the second chi ller is started and is running, the lead ch iller shall monitor
conditions and eva luate whether the capacity has r educed enough fo r the lead chiller t o sustain
the system alone. If the capacity is reduced enough for the lead chiller to sustain the CONTROL
POINT temperatures alo ne, then the operatin g lag chiller is stoppe d.
If the lead chiller is stopp ed in CCN mode for any reas on other than an alarm (*) c on dition,
then the lag and standby chi llers are stopped. If the configured lead c hi ller stops for and ala rm
condition, then the configured l ag chiller takes the lead chille r’s place as the lead chiller and t he
standby chiller serves as t he lag chiller.