Emerson Liebert ICOM-DO User Manual download pdf (Page 39)

Operation

3.7 Supply Control

3.7.1 Supply Air

The Supply Air sensor can be used to control, limit or reference the discharge air temperature of the

cooling unit. The desired supply sensor operation can be selected in the Service, Setpoints menu. The

optional supply air temperature sensor allows use of either the Supply Air control or the Supply Limit

control. This sensor can be added to existing Liebert iCOM controls by purchasing the supply sensor

and wiring harness. The supply air sensor must be connected to P13 pins 1 & 2. Contact your local

Emerson representative for pricing and installation.

• Supply Control: When the supply sensor is set to Control, the unit will control the amount of

cooling / heating being provided based on maintaining the discharge air temperature. The return

air sensor will still control the humidity of the room.

• Supply Limit: Chilled water units may be set up with the supply air sensor to maintain a mini-

mum air temperature under a raised floor to help prevent condensation. In order to avoid supply

temperatures that are too low, the Supply Limit can influence the opening of three-point or ana-

log actuators or the output of analog values. The control compares the deviation from the return

air setpoint and the supply limit setpoint, and calculates the output to the actuator from the

smaller deviation.

• Cooling Only: When Cooling Only is selected, the cooling capacity of the system (valve or com-

pressor) is modulated based on the supply temperature, but allows the fan speed to be controlled

by a different sensor.

• Disable: Setting the supply sensor to Disable will allow the supply sensor to be monitored but

will not affect the control output of the unit.

When the supply air sensor is set up for Supply control, additional Supply Air configuration

parameters (valve pulse, cooling filters and return compensation) can be used to further enhance

the supply air control.

• The valve pulse and cooling filter timer can be adjusted to prevent oscillating around the supply

setpoint and still allow for rapid valve adjustments to compensate for heat load changes. Contact

your local Liebert service personnel for adjustments.

• Return Compensation begins to increase the supply air setpoint when the return air decreases

below the return air setpoint.

Example

Setting the return compensation value in the Service, Setpoints menu to 5°F (2.7°C) will

increase the supply setpoint from 50°F to 55°F (10°C to12.8°C) when the return temperature is

at the low limit of the proportional band.

NOTE

If unit is equipped with a 3P actuator type valve then the valve must be changed to utilize the

feedback signal. See 3.2.3 - Chilled Water Control.

NOTE

Supply control and limit are calculated on each unit, independent of the other sensor readings

on the network.

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Emerson Liebert ICOM-DO User Manual Page 39