Sterlco S Series Central Chilling Stations - Manual (Page 28)

Page 28 of 77 SCW Series Central Chilling Stations
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
infinitely unloaded or turned on/off to keep the temperature
at the specified set-point.
2. Compressor anti-recycle time is two (2) 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.