Liebert 50 & 60Hz User Manual

This function shows the interval time at which the system will perform a modulating chilled-water 

valve system flush cycle. The factory default is 24 (hours) and is programmable from 0 (hours) which 

signifies to never flush, to 99 (hours) which signifies to flush after every 99 hours of valve non-use. If 

the valve is called on by the control to open within the programmed interval time, the timer will be 

reset to 0. The flush cycle is active even when the fan is turned off, but power is applied to the unit. 

When the interval timer reaches the programmed time, the valve will be opened for 3 minutes to flush 

any contaminates which may have collected in the system.

The display will prompt the operator to enter a three digit password when attempting to make 

changes. The system includes two (2) passwords, one for setpoints and one for setup. The system 

allows the password to be changed by first entering the default password set at the factory (1-2-3) for 

setpoints and (3-2-1) for setup. The password function provides system security, so that only autho-

rized personnel are allowed to make changes to the system. (If unauthorized changes are being made, 

the passwords may be compromised and new ones should be selected). The password function can be 

disabled by setting DIP switch 8 in the wallbox to OFF, then resetting power to the unit.

The temperature and humidity sensors can be calibrated by selecting the CALIBRATE SENSORS 

menu item. The temperature sensor can be calibrated ±5°F, while the humidity sensor can be cali-

brated ±10% RH. When calibrating the humidity sensor, the value shown will always be % RH, even 

though absolute humidity control may be selected. If absolute humidity control is selected, the Nor-

mal Status Display will display the adjusted reading. This reading may not agree with the relative 

humidity reading displayed while in calibration.
If the sensors are subject to frequent wide temperature and humidity swings, it may be necessary to 

shorten the cycling by increasing the sensor response time delay. If the sensors are located too close to 

the air discharge, they will likely experience rapid swings in measurement. The factory default is 30 

seconds. Another method in reducing compressor cycling is to increase the temperature and/or humid-

ity sensitivity.

Each alarm can be disabled or enabled. Use the UP/DOWN ARROW to select a particular alarm, 

press Enter to select either enable or disable. Then press Enter again to store the change. When the 

alarm is disabled it will NOT report to either the wallbox beeper or the common alarm relay. The high 

water in condensate pan and high head alarms cannot be disabled.

Restart Time Delay

0.1

0 to 9.9 min

(0 = manual restart)

C/F Degrees

°

F

°

C or 

°

F

Humidity Control

Rel

Relative or Absolute

Valve Time

165

50 to 250 sec(s)

CW Flush

24

0 to 99 hours