Emerson Liebert iCOM Manual De Usuario

S135 DT1 (Room / Outdoor) Type sets the activation point of the ambient dry bulb outdoor 

temperature as it relates either to an indoor actual temperature or to the temperature setpoint 

programmed on line S136. If S135 is set to “Temp,” the outdoor dry bulb temperature is compared to 

the return temperature actual value. If set to “Set,” the outdoor dry bulb temperature is compared to 

the return temperature setpoint. If set to “Disable,” the outdoor temperature will not be compared to 

the return sensor value for activation. When set to “Temp” or “Set,” the outdoor temperature must be 

lower than the room temperature setpoint or the actual return temperature sensor reading.
In most applications, this parameter will be set to “Temp” because the outdoor air temperature will 

reduce cooling costs as long as the outdoor air is below the return air temperature to the primary 

cooling unit. This remains true even when the outdoor temperature is higher than the supply control 

setpoint. The following examples assume that the unit is set for supply air control and that the 

moisture content of the outdoor air is within the allowable range.

The conditions in this example would result in a reduction of 10°F entering the unit and would extend 

the operating range of the Liebert Air Economizer

™

. The outdoor damper would be 100% open and the 

mechanical cooling would be utilized to achieve the 60°F (16°C) supply temperature setpoint.

In this example, the cooling unit would not use outdoor air because it is warmer than the actual 

return temperature to the CRAC.

In this example, the cooling unit would open the outdoor damper based on the amount of cooling 

needed to satisfy the supply air temperature setpoint. The unit should be able to satisfy the supply air 

setpoint with Liebert Air Economizer operation only.
If SA04 through SA06 status indicate OK, but the room temperature is not maintained, SA07 Stop 

ECO at Setpoint + will disable the Liebert Air Economizer and activate the next cooling source.