If the configured lead ch ill er does not complete the star t -up before the PRESTART FAUL T
TIMER (user co nfigured value) elapses, then the lag chiller sh all be started and the lead ch iller
will shut down. The lead ch ill er then monitors the sta r t req uest from the acting lead c hi ller to
start. The PRESTA RT FAULT TIMER is initiated at the ti me of a start reques t. The PRESTART
FAULT TIMER’s functio n is to provide a timeout in the ev ent that there is a prestart ale rt
condition preventi ng t he machine from starting in a timely manner. The tim er is c onf igured
under Lead/Lag, foun d in t he Equipment Configurat ion table of the Servic e m enu .
If the lag chiller does not achieve start-up before the PRESTART FAULT TIMER ela pses,
then the lag chiller sha ll be stopped and the standby c hil ler will be requested to star t , if
configured and ready.
Standby Chiller Configuration and Operation
The configured standby c hi ller is identified as such by ha ving the LEAD/LAG SELE CT
configured to the val ue of ‘‘3.’’ The st andby chiller can only o perate as a replacem ent for the lag
chiller if one of the othe r two chillers is in an alarm (*) con dition (as shown on the LID pa nel). If
both lead and lag chiller s ar e in an alarm (*) condition, th e standby chiller shall def ault to
operate in CCN mode based on its configured Occupancy S c hed ule and remote contact s input .