Emerson Liebert ICOM-DO User Manual download pdf (Page 20)

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Operation

Chilled Water Units with Variable Fan Speed—EC or Variable Frequency Drives

VSD Fan Speed parameter can be found in the Service Menu / Setpoints submenu on page 5 of 6. This

menu allows the cooling unit's fan motor speed to be configured and adjusted for a variety of applica-

tions.

• Auto Operation: When set to Auto, the speed of the fan motor follows the position of the chilled

water valve based on predetermined logic for cooling and dehumidification operation. Auto opera-

tion can be set with either return or supply air control.

• Manual Operation: When set to Manual, the speed of the fan motor follows user input as set

either locally at the Liebert iCOM display or remotely via a Modbus signal with an optional Lie-

bert IntelliSlot® 485 card.

• Economy Operation (GLYCOOL or dual-cool units only): When set to Economy, the speed of the

fan motor follows the Free Cooling or Dual Cool water valve. The fan speed will go to the STD set-

point (Service Menu, Setpoints) when a compressor activates to prevent pre-cooling of the DX coil.

• Delta Operation: When set to Delta, the speed of the fan motor is controlled by two temperature

sensors (optional). The sensor temperature readings will be compared and a delta between the

two sensors will be determined. The delta of the two sensors will be compared to the fan speed

delta setpoint and will determine the correct fan speed. This control can be adjusted using the

Fan Speed P-Band and the Fan Speed Integration to determine the rate of change based on the

sensor delta. Delta operation enhances air flow control when a containment solution is being uti-

lized. This is accomplished by maintaining the correct airflow based on the inner and outer con-

tainment temperatures.

• Return Operation: When set to Return, the speed of the fan motor is controlled by the return air

sensor and the cooling capacity is controlled from the supply sensor (optional). This allows the

return air sensor to be left in the return air of the unit or placed remotely. If placed remotely

make sure that the sensor is mounted with the connected unit's area of influence.

Additional fan speed configuration parameters include a fan speed filter and fan speed reposition

delay timer. These parameters allow the fine tuning of the fan speed control and can be applied to any

control mode except Manual.

• The fan speed filter allows the fan to react differently depending on the location of the control

point within the proportional band.

Example: When the temperature is close to setpoint or lower in the proportional band the fan

speed changes are slow to avoid overshooting the setpoint. However, when the temperature is fur-

ther away from setpoint or higher in the proportional band the control will respond quickly.

• The fan speed reposition delay timer can be adjusted to prevent the fans from oscillating. This

delay timer will only allow the fan speed to decrease when the timer expires. Increases in fan

speed are not limited by this delay.

VSD Setpoint (VSD Fan Speed Setting)

If the VSD Fan Speed Control (Service Menu, Setpoints) is set for Manual, the VSD Fan Speed Set-

point (Service Menu, Setpoints) may be set for the desired speed of the variable speed motor.

Depending on the product control design, there may be an internal minimum speed, as defined by

that specific product operation, while the customer input may be set for 0-100%:

• Fan speed may be set locally at the unit using the Liebert iCOM display.

• Fan speed may be set remotely via a BMS signal (sent via Modbus using an optional Liebert Intel-

liSlot 485 card), which then transmits to the unit local control.

NOTE

• The fan speed lower and upper limit settings are defaulted to 60% and 100%. These

parameters can be adjusted to operate at any point between the default settings.

• The standard fan speed control will be overridden during a call for Dehumidification. When

there is a call for Dehumidification, the fan speed will change to the VSD Setpoint Dehum

parameter found in the Service Menu, Setpoints.

• The standard fan speed control will be overridden during a call for Humidification or

Reheat. During a call for Humidification or Reheat ,the fan speed will change to 100% to

eliminate the possibility of condensation or damage to the unit.

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Emerson Liebert ICOM-DO User Manual Page 20

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