Lag Chiller Start-Up Requirements
Before the lag chiller c an be started, the following conditions must be met:
1. Lead chiller ramp loading must be complete.
2. Lead chiller CHILLED WATER temperature must be greater than the CONTROL POINT
plus 1/2 the WATER/BRI NE DEADBAND.
Note: The chilled water te mperature sensor may b e the leaving chill ed water sensor, th e return
water sensor, the comm on s up ply water sensor, or th e c om m on return water sensor,
depending on which optio ns are configured and enab led.
3. Lead chiller ACTIVE DEMAND LIMIT value must be greater than 95% of full load amps.
4. Lead chiller temperat ure pulldown rate of the CHILLED WATER temperatur e is less than
0.5° F (0.27° C) per minute.
5. The lag chiller status indi cates it is in CCN mode and is not fa ulted. If the current lag c hil ler
is in an alarm condition, then the standby chiller be comes the active lag chi ller, if it is
configured and avail able.
6. The configured LAG STA RT TIMER entry has elapsed. The LAG START TIMER shall be
started when the lead chi ller ramp loading is com pl eted. The LAG STARTTIME R en try is
accessed by select ing Lead/Lag from the Equipm en t Configuration tab le of the Service
menu.
When all of the above requi rements have been met, t he la g chiller is forced to a STAR T
mode. The PIC control t hen monitors the lag chiller for a successful start. If the lag chille r fails to
start, the standby chill er, if configured, is star t ed.