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Emerson iCOM Digital Scroll Compressors, Digital scroll capacity modulation, 10-100% variable

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Operation

Digital Scroll Compressors

A compressor with a suction cutoff unloader can only modulate its capacity between two distinct lev- els: fully loaded and half loaded. A digital scroll compressor can modulate its capacity anywhere between 10-100%. This variable capacity modulation allows cooling units to control an environment more precisely.

Digital scroll capacity modulation is achieved by energizing and de-energizing a solenoid valve on the compressor. When the solenoid valve is de-energized, the compressor capacity is 100%. When the sole- noid valve is energized, the compressor capacity is zero. Therefore, the capacity of the compressor depends on how long the solenoid is de-energized for. If the solenoid is de-energized for 10-seconds, then energized for 5 seconds during a 15-second cycle, the resulting capacity will be 66% as shown in Figure 15.

Figure 15 Digital scroll capacity modulation, 10-100% variable

Call for Cooling: 66% 100% Loaded

Solenoid

De-energized

0% Loaded

Solenoid Energized

Solenoid

De-energized

Solenoid Energized

0		5	10	15		20	25	30

		15-Second Capacity				15-Second Capacity
		Modulation Cycle				Modulation Cycle

On single and dual digital scroll compressor systems, the first compressor is started at 25% calculated output from the temperature proportional band and stopped at 10%. On dual digital scroll compressor systems, the second compressor is started at 35% and stopped at 20%, see Figure 16. When a com- pressor is started, the solenoid is energized longer than it is de-energized to match the call for cooling. When the call for cooling increases to 100%, the solenoid is de-energized for the entire 15 second cycle.

Figure 16 Single and dual digital scroll compressor activation points

Temp Setpoint: 70°F					Comp 1 & 2 On
Temp Setpoint: 70°F					Fully Loaded
Proportional Band : 8°F			Comp 2 On Partially		Fully Loaded
Proportional Band : 8°F			Comp 2 On Partially
Deadband : 2°F			Loaded
	Comp 1 On Partially
½ Dead-		Loaded
½ Dead-
band
70	71	72	73	74	75
0%	Comp 1				+ 100%
0%	Comp 1				Cooling
Cooling	Off				Cooling
Cooling	Off

Comp 2

Off

½ Proportional Band

Increasing Temperature

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Emerson iCOM user manual Digital Scroll Compressors, Digital scroll capacity modulation, 10-100% variable

Contents

Liebert iCOM Page Table of Contents Mounting a Large Display on a Wall Installing a Liebert Icom UNIT-TO-UNITNETWORKTeamwork Figures Tables Features Large and Small Displays ESC Keyboard icons and functions Icon Key Name Function Status menu, large display, graphical view Accessing Submenus on Large Displays Accessing SubmenusAccessing Submenus on Small Displays Navigating Through the Liebert iCOM Menus Entering a Password Menu tree-Small display, stand-alone or networked Advanced Menu Unit Service Menu UnitStatus Menu System View Status Menu Unit 1 View User Menu Advanced Menu Unit # Service Menu Unit #Viewing Multiple Units with a Networked Large Display SET User menu icons Service menu icons Single Unit Functions Unit/Fan Control Start Stop VSD Setpoint VSD Fan Speed Setting Loss of Power AlarmFan Alarm / Fan Protection Settings Autorestart High Pressure Alarm Pump Down Compressor Sequencing Digital Scroll High TemperatureCompressor Timing-Units With Two Compressors MBV Operation After Compressor is Turned Off Service Offset-Changing System Pressure SettingsMotorized Ball Valve in Digital Scroll Units Temperature Proportional Band Temperature proportional band One Single-Step Compressor Without Unloaders-One-Step Compressor ControlCompressor Proportional Bands Two Single-Step Compressors Without Unloaders-Two-Step Two Compressors With Unloaders-Four-Step Two compressors with unloaders four-step Digital Scroll Compressors Digital scroll capacity modulation, 10-100% variable Delta T Temperature Difference Between Room and Glycol Temperature Control-Second Cooling SourceDifferential Temperatures / Controls Comparator Circuit Chilled Water Control Second cooling source and compressorized cooling Glycool Cooling-Free-Cooling Temperature Control-ReheatReheat configuration types Dual Cooling Source Off ½ Proportional Band Decreasing Temperature Heat On ½ Dead Band 100% Tight Mode SCR Reheat Standard Mode Humidification Humidity ControlHumidification Dehumidification External Humidifier Control-Optional Humidification Infrared HumidifierParameters for infrared humidifier control Dehumidification Low Limit Dehumidification With Comp settingsDehumidification Dehumidification Compressor Quantity Reheat During Dehumidification Temperature and Humidity Control TypesControl Types Humidity Sensor Reading Control Types High and Low, Temperature and Humidity Events Supply Limit-Optional User Inputs / Customer Inputs Customer inputs Event Types and Properties Time DelayEnable or Disable Event Types Main FAN Overload Possible Event Notifications Event notifications-large or small display Calculating Unit Wellness Next Maintenance CalculationCalculation of Next Maintenance and Diagnostics Fans / Heaters / Humidifier Settings and Diagnostics Parameters for Next Maintenance CalculationGeneral Maintenance Settings Compressor 1 / 2 Settings and Diagnostics Application of Teamwork Modes Teamwork ModeTeamwork Modes No Teamwork Teamwork Mode 1 with two cooling units Standby Rotation Typical Standby Lead/Lag Function Standby and Cascade Minimum Network Switch Requirements Placement of Cooling UnitsU2U Hardware Cables and Network Switch Liebert iCOM U2U Ethernet Network Wiring for Unit-to-Unit Communications-U2USample Liebert iCOM network configurations Wall-Mount Large Display Wiring a Liebert iCOM U2U Network Small DisplaysLarge Displays Combining Large and Small Displays on a U2U Network Wiring a small display for stand-alone operation Wiring a large display for stand-alone operation Ports available for connecting Liebert iCOM control devices Liebert vNSA 298 84mm 305mm 14.25 362mm DPN001136 Rev Mounting Instructions Location ConsiderationsNecessary Mounting Items Liebert iCOM display dimensions Spare part list parameters-large display only Spare Part List-Large Display OnlySetpoints parameters Event log parameters Set alarms parameters Sensor data Display setup parameters Active AlarmsActive alarms parameters Timer parameters-Sleep Mode Total run hours parameters Service contacts parameters Service Menu Parameters Unit Diary-Large Display Only Unit diary parameters Standby settings / lead-lag parameters Maintenance / wellness settings parameters Wellness COMP2 Wellness HEAT2 Diagnostics / service mode parameters ALM REL 7of Delay Enable Disab Enable Disab Comp 1 Overload Unit X Disconnected WRN Loss of Power LOP MSG, WRN, ALM Call Service MSG, WRN, ALM High Temperature Sensor calibration / setup parameters System / network setup parameters-large display only Network setup parameters GBP Static RAM Not Available, Invalid, OK Options setup parameters HUM Steam Service contact info parameters Service Menu Parameters Service Menu Parameters Page Ti n Ne tIti That