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Ultra-Aire MD33 Installation Instructions
The Ultra-Aire MD33 has an illuminated display, user selectable setpoint, and a power ON / OFF button located
behind the diffuser. The diffuser is fastened with tamper resistant screws to limit access to the control. The diffuser
can also be fastened with the included phillips screws if limiting access to the control is not needed.
When turning power on for the first time, the set point will be at the factory setting of 55% RH. In the event of
a power outage, the dehumidifier restarts at the previous set point when power is restored.
Pressing the middle button (the power button), the control will toggle the Ultra-Aire MD33 to turn ON or OFF.
If the unit is on and power button is pressed, control will turn compressor and fan off. As a result, both DISPLAY
and LED will go off.
If the unit is off and power button is pressed, control will turn fan on. As a result, both DISPLAY and LED will
go on.
If there is an error, the unit will shut down and indicator LED will turn to red and display will show an error code
(see page 14 for error codes).
Sequence of Operation
1. Press the ON
/
OFF button to turn the dehumidifier control on. The display will show “00” for a couple of
seconds and then it will display the RH level of the room and the dehumidifier blower will turn on to start
sampling the air for one minute.
Indicator LED, located above display, will be green, showing the unit is operating normally.
2. Pressing either of the arrow keys will cause the DISPLAY to flash and indicate the current set point. The RH set
point can be adjusted from a minimum of 35% to a maximum of 99% in 1% increments. Adjust the humidity set
point as desired. The recommended initial setting is 55%.
Pressing the DOWN arrow key below the 35% set point on the control will cause the display to read “00” and
the Ultra-Aire MD33 will run continuously. After 10 seconds, it will go back to display room RH level.
Ten seconds after making an adjustment, from either UP or DOWN arrow keys, the display will go back to show
the room RH level.
3. If the sensor detects a reading above the set point, it will run the fan to sample the return air for a period of one
minute. The sampled humidity of the return air will be compared to the RH setting. If the humidity is above the
setting, the dehumidifier compressor turns on. The compressor remains on until the measured humidity falls 3%
below the RH setting. If the sampled humidity is below the setting, the compressor and blower turn off and the
display returns to showing the RH setting. The dehumidifier will sample again every 15 minutes.
CONTROLS
