Free Cooling Flush Duration
Length of time the for flush of the free cooling coil.
Free Cooling Flush Starts K11
When enabled, the Q15 relay is activated during the free cooling flush.
Ramp Up Fan at 100% FC
Enables/disables an increase in fan speed when free cooling reaches 100% capacity.
7.1.4 Temperature Control with a Fluid Economizer
When an economizer is installed, the cooling requirement (determined by the temperature proportional band) is addressed
first by the economizer’s secondary cooling, if the economizer cooling capacity is insufficient, the compressor(s) begin cooling
to bring the room air temperature down to the temperature setpoint.
The fluid economizer employs a motorized ball valve that controls the flow of chilled water/glycol to provide a cooling
capacity from 0%to100%.
Simultaneous Operation, Partial Economizer Operation, and Staging Cooling Sources
When simultaneous operation of the compressor(s) and secondary cooling is enabled, the portion of the proportional band
assigned to the fluid capacity valve may be reduced by the comparator circuit based on the DT settings. When this occurs,
the compressor control proportional band moves closer to the setpoint, and compressorized cooling begins before secondary
cooling reaches 100% (as shown in the example Secondary Cooling Temperature Control with Two Step Compressor on the
facing page ) or shuts off.
CAUTION: On units with a GLYCOOL fluid economizer and standard scroll or semi-hermetic compressors
without unloaders, there is a risk of over cooling and low refrigerant pressure when free cooling/secondary
cooling operates simultaneously with compressor/DX cooling. Make sure adequate flow is provided when
100% free cooling and compressorized cooling occur at the same time. If the fluid temperature is too cold
while the compressors are running, the refrigerant pressure will drop. Contact technical support at 1-800-
543-2778, opt. 5 for more information on setting up simultaneous operation.
NOTE: The compressor control method is not affected by economizer operation and operates across the assigned
proportional band based on the compressor configuration of your system (1 step, 2 step, 4 step, or digital scroll). See
Compressor Control by Cooling Requirement on page29 , for a description compressor control methods.
7 Configuring Economizer Operation
112
Vertiv™ Liebert® iCOM™Installer/User Guide
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