Vertiv Liebert iCOM DP400/500 Installer/User Manual page 32

Digital Scroll Compressors
Digital scroll compressors use time loaded/unloaded to modulate cooling capacity between 10% and 100% to control
cooling more precisely than non-digital compressors. Capacity modulation is achieved by opening and closing a digital
solenoid valve in 15 second intervals while the compressor runs continuously when the cooling requirement is 10% to 100%.
• When the valve is opened (energized, the compressor is unloaded and capacity is 0% (because the scroll
plates are separated so that there is no refrigerant flowing through the compressor).
• When the valve is closed (de-energized), the compressor is loaded and capacity is 100%.
• Capacity is determined by the amount of time that the valve is closed in the 15 second interval. Figure 3.3
below illustrates solenoid-valve operation when cooling requirement is 66%.
• The valve is closed for 10 seconds (100% cooling).
• Then open for 5 seconds (0% cooling).
• This results in 66% cooling. Essentially, the compressor is partially loaded.
Figure 3.3 Digital Scroll Compressor Operation to Provide 66% Cooling Capacity
24
No. Description
1 Solenoid de-energized.
2 Solenoid energized.
3 Percent loaded.
4 15 second capacity modulation cycle.
Vertiv™ | Liebert® iCOM™ Installer/User Guide