Emerson Liebert Deluxe System/3 DH - Manual (Page 34)

Advanced Microprocessor with Graphics Control Setup
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4.7.6 Select Humidity Sensing Mode
This screen permits the user to select between RELATIVE (direct) and ABSOLUTE (predictive)
humidity control. If relative is selected, the RH control is taken directly from the RH sensor. If abso-
lute is selected, the RH control is automatically adjusted as the return air temperature deviates from
the desired temperature setpoint. This results in predictive humidity control. The display will indi-
cate % RH for both methods of control, but the adjusted humidity reading will be displayed if absolute
is selected. With predictive humidity control, the humidity control is automatically adjusted approxi-
mately 2% RH for each degree difference between the return air temperature and the temperature
setpoint.
With relative humidity control, unnecessary dehumidification can result when overcooling occurs dur-
ing a dehumidification cycle. This is because a higher than normal RH reading is caused by overcool-
ing the room (about 2% RH for each degree of overcooling). This 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 overcooling was significant
enough, the RH could be low enough to activate the humidifier.
If absolute humidity control is selected, over-dehumidification is avoided. When overcooling occurs,
causing an increase in the RH reading, the humidity control program “predicts” what the RH will be
when the dehumidification cycle ends and temperature returns to the setpoint. This allows the dehu-
midification cycle to end at the proper time. The predictive humidity control can reduce energy con-
sumption by minimizing compressor and reheat operation, and eliminating unnecessary humidifier
operation.
4.7.7 Set Status Display
The Status Display can be set to show the return air temperature and humidity SENSOR READ-
INGS or the temperature and humidity control SETPOINTS through this selection. When setpoints
are selected, the Status Display indicates so by also displaying “SETPOINTS”. If SENSOR READ-
INGS is selected, the Status Display will show the return air sensor readings.
4.7.8 Change Passwords
Selecting Change Passwords will prompt the user to select one of the following:
• SETPOINT PASSWORD
• SETUP PASSWORD
The display prompts you to enter a three digit password when making changes. The system includes
two (2) passwords, one for setpoints and one for system setup. The system allows the passwords to be
changed by first entering the present password, factory set as “123” for setpoints and “321” for setup.
The password function provides system security, so only personnel authorized to make changes
should know the passwords. If unauthorized changes are being made, the passwords may be compro-
mised and new ones should be selected. The password function can be disabled by setting DIP switch
8 to OFF.
4.8 Main Menu (AG)—Run Diagnostics
By selecting Run Diagnostics, maintenance personnel can check system inputs, outputs, and complete
a test of the microcontroller circuit board, all from the front panel. Review of the system inputs and
the microcontroller test can be done without interrupting normal operation.