8.9.1 Restart Time Delay
This function delays unit restart after main power is restored to the unit. If several systems are operating,
the time delays should be set to different values to cause a sequential start. Delay can be set from 0.1
minutes to 9.9 minutes (6 seconds to 594 seconds). Setting the value to zero (0) will prevent the unit from
restarting when power is restored. In this case, the unit must be restarted manually by pressing the
“ON/OFF” button on the keypad.
8.9.2 C/F Degrees
The control may be selected to show readings and setpoints in either degrees Fahrenheit (°F) or Celsius
(°C). To change the value use Enter to select this function, then use the Up and Down arrows to change
the value. Press Enter to store the value.
8.9.3 Humidity Control Method
The operator may select either relative (direct) or absolute (predictive) humidity control. If “relative” is
selected, the RH control is taken directly from the RH sensor. If “absolute” is selected, the RH control is
automatically adjusted whenever return air temperature deviates from the desired temperature setpoint
(i.e., predictive humidity control). The LCD display will indicate percentage relative humidity for both
methods of control. If the “absolute” feature is selected, the adjusted humidity reading will also be shown.
When utilizing the predictive humidity control feature, the humidity level is automatically adjusted ~2%
RH for each degree difference between the return air temperature and the temperature setpoint.
Unnecessary dehumidification can result when overcooling occurs during a dehumidification cycle. This
is due to a higher than normal RH reading caused by overcooling the room (about 2% RH for each degree
of overcooling). This drop in temperature extends the dehumidification cycle. Later, when the
dehumidification ends and the temperature rises to the setpoint, the RH reading falls. The final RH
reading will then be lower than actually desired. If the temperature drop was significant enough, the
percentage RH could be low enough to activate the humidifier.
If the absolute humidity control is selected, over-dehumidification may be avoided. When overcooling
occurs (i.e., causing an increase in the RH reading) the humidity control program estimates what the RH
will be when the dehumidification cycle ends and temperature returns to the setpoint. This allows the
dehumidification cycle to end at the proper time. Predictive humidity control can greatly reduce energy
consumption by minimizing both compressor/reheat operation. Use the UP or DOWN arrow key to select
the desired humidity control method.
8.9.4 Show DIP Switch
This function shows the position of the DIP switches, which are located on the control board in the unit; 1 =
Switch is “ON” and 0 = Switch is “OFF.” For more information on the DIP switches and their functions, see
Table 8.5 on page63.
8.9.5 Valve Time (for Systems With a Modulating Chilled Water Valve)
This function shows the full valve travel time of the modulating valve on a chilled water system. This is the
time it takes for the valve to travel from full closed to full open. It is programmable from 50 to 250 seconds;
factory default time is 165 seconds and should not be changed. The full valve travel time is used by the
control to determine the appropriate valve position. For example, if the valve travel time is 165 seconds
and 50% cooling is being called for, the valve will open for 83 seconds to achieve 50% open.
Vertiv | Liebert Mini-Mate2—5 ton User Manual| 59
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