Sterling SCW Series installation manual Staging, Alarms, Lead-Lag Compressors, Lead-Lag Pumps

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.

Page 28 of 77 SCW Series Central Chilling Stations