Supply Control; Supply Air - Emerson Liebert Challenger 3000 User Manual

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.
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.
• 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.
NOTE
Supply control and limit are calculated on each unit, independent of the other sensor readings
on the network.
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.
33
Operation