Emerson PFH020A-L, User Manual

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Microprocessor Control
43 Liebert
®
Mini-Mate2
™
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/Down Arrows to
change the value. Press Enter to store the value.
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.
In terms of relative humidity control, 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. The predictive humidity control can greatly
reduce energy consumption by minimizing both compressor/reheat operation and elimination
unnecessary operation. Use the Up/Down Arrows to select the desired humidity control method.
6.1.8 Change Passwords
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 set (12-3)
for setpoints and (3-2-1) for setup. The password function provides system security, so that only
authorized 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 wall box to OFF.
Table 18 Setup functions, default values and allowable ranges
Function Default Range
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