Sterlco S Series Central Chilling Stations - Manual (Page 27)

SSC Series Central Chilling Stations Page 27 of 86
4 Sequence Of Operation
4-1 Staging
1. The system uses a PID control algorithm to regulate the
chilled water temperature. As the required control effort
increases or decreases, the system compressors are turned
on or off to keep the temperature at the specified set-point
2. Compressor anti-recycle time is three (3) minutes.
4-2 Alarms
If a fault occurs, that compressor or circuit is deactivated. The
load will automatically shift to any other compressors that are
currently ON-LINE, but not running. Lead/Lag rotation will
continue to function. Compressors that are faulted will be
removed from the rotation order.
4-3 Lead-Lag Compressors
The system automatically rotates the compressor order to generate
a Lead/Lag rotation. Any time a compressor is faulted or manually
taken OFF-LINE, it will be removed from the Lead/Lag rotation.
Once the fault is cleared or manually put ON-LINE, the
compressor is returned to the Lead/Lag rotation at the end of the
rotation order.
4-4 Lead-Lag Pumps
The system automatically rotates the pump order to generate a
Lead/Lag rotation. Any time a pump is faulted or manually taken
OFF-LINE, it will be removed from the Lead/Lag rotation. Once
the fault is cleared or manually put ON-LINE, the pump is returned
to the Lead/Lag rotation at the end of the rotation order.