NOTICE
Risk of high or low humidity. Can cause environmental conditions that are outside equipment requirements.
While the Liebert® Air Economizer is operating, the primary cooling unit’s humidification and dehumidification are
inhibited. If humidity level is important to operational requirements, it must be controlled by other methods
during operation of the Liebert® Air Economizer. While the primary cooling unit is cooling without the Liebert® Air
Economizer, the primary cooling unit will control humidity levels according to its setpoints.
NOTICE
Risk of freezing temperatures. Can cause equipment and property damage.
Low outdoor temperatures can produce freezing conditions that adversely affect cooling systems employing
water, particularly when the water is not moving through the pipes. When cooling system water is not moving,
frozen waterlines, burst coils and water damage are possible. The outside damper must be set so that it is fully
closed when freezing temperatures are possible and the cooling system is not operating. See Disable the Vertiv™
Liebert® Air Economizer on page79 This can be achieved by either connecting a freeze stat that interrupts the
economizer signal or by wiring a freeze stat directly into the Liebert® iCOM™’s customer input.
The risk of freezing is increased unless the proper amount of glycol is added to the chilled water unit loops.
NOTICE
Risk of infiltration of odors, smoke and particulates from outside air. Can cause environmental conditions that are
outside equipment requirements.
The Liebert® Air Economizer does not remove odors, smoke, gases or particulates from the outside air used for
cooling. These must be controlled by other methods.
When the Liebert® Air Economizer is being used for cooling, both the outside air damper and the room return air damper are
active in an opposing relationship. The cooling requirement and temperature of the outdoor air will determine the position of
the outside air damper. It will range from fully closed to fully open. As the outside air damper moves toward fully open, the
return air damper will close to a minimum of 15%. The 15% minimum is to make sure that air remains circulating near the return
air sensor. If the return air sensor is moved to another position where there is constant circulation of air in both outdoor and
indoor modes, then the minimum 15% indoor damper position can be removed.
NOTICE
Risk of improper operation. Can cause degraded cooling and ventilation operation because of improper building air pressure.
The incoming air from the outside damper requires expelling an equal volume of air through a field-provided powered relief air
vent. The volume that must be expelled will vary from 0 to 80% of the total airflow for all Liebert® Air Economizer units. The
powered relief system should be sized for 80% of the total airflow for all Liebert® Air Economizer units in the conditioned
space and to maintain minimal building air pressure.
3.5.1 Liebert® Air Economizer System Overview
The objective of the Liebert® Air Economizer is to expel warm air from the conditioned space and bring in cooler air through
the Liebert® Air Economizer. This function is monitored continuously by the Liebert® iCOM™
Figure 3.21 on the facing page below shows an example of the air flow pattern of a Liebert® Air Economizer system. The
indoor sensor must be positioned where there is airflow when the system is in full economizer operation and when the system
is operating in non-economizer mode.
If the indoor damper position has been changed to 0% from the factory default of 15%, then the indoor sensor must be moved,
preferably to the hot aisle.
3 Service Operation
76
Vertiv™ Liebert® iCOM™Installer/User Guide
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