Vertiv Liebert iCOM - Page 43

Figure 3.8 Compressor Control—Single Digital Scroll Compressor
No. Description
1 Digital scroll begins operation
2 Digital scroll operation at 100%
3 ½ of proportional band
4 Deadband
Dual Digital Scroll Compressors
In a two digital scroll system, the compressors operate in a lead-lag configuration:
• The lead compressor starts when the cooling demand is at least 25% (calculated from temperature proportional
band) and operates at 50% capacity (valve open 7.5seconds/closed 7.5seconds) for an initial period set in
Winter Start Delay (see Setting Low Pressure Time Delay on page59 ), after which it operates per cooling
demand.
• The lag compressor starts when cooling demand is 35% and operates at 70% capacity, increasing capacity as
cooling demand increases.
• On both compressors at 100% cooling requirement, the valve remains closed for the entire 15 second interval and
the compressors operate loaded at 100% capacity.
• The lag compressor stops when the cooling demand decreases to 20%.
• The lead compressor stops when cooling demand decreases to 10%.
3 Service Operation
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Vertiv™ Liebert® iCOM™Installer/User Guide