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Scholar V VAIVA Maintenance & Service Manual 10/2017 Rev.2
9.1 HMI MODES OF OPERATION
Be sure all installation steps have been completed and double checked. Check the
voltage and phasing to be sure they are correct. Be sure breakers have been sized
properly. Be sure wire has been sized properly. Turn on the circuit breakers to provide
power to the unit. After a few seconds, the HMI display will activate.
Refer to the HMI Screen Navigation section shown above.
Start with HMI showing Screen 1 (Main Screen)
• Set Occupied or UnOccupied as desired
• Set Pre-Conditioning On or Off as desired
• Set Blower Auto or Blower ON as desired
• Be sure desired set points have been entered for all modes
Cooling
• Press the Cooling button on Screen 1. If the room temperature is greater than or
equal to the cooling set point, the compressor should start. This may take up to 60
seconds, based on the setting of the ASCT setting.
• One or both outdoor coil blowers should come on. This may take a few seconds,
especially if the outdoor air is cool. (See Head Pressure Control).
• The indoor blower should come on. It will run continuously if the blower is set to ON,
It will cycle with the compressor if set to AUTO. If set to AUTO, it will run for a period
of time after the compressor turns off, based on the Post Purge time setting.
• If the room temperature is considerably higher than the cooling set point, the com-
pressor speed will ramp up slowly until the maximum control voltage is provided to
the compressor controller. This sets the maximum compressor speed and maximum
unit cooling.
• If the room temperature is slightly below the cooling set point, the compressor
speed will ramp down until the minimum voltage is provided. This sets the minimum
compressor speed.
• When the room temperature is approximately equal to the set point (inside the
control band explained in Screen 4), the compressor speed stops changing and
stays fixed.
• As the compressor speed changes, the indoor blower speed will also change. The
higher the compressor speed, the higher the indoor blower speed.
• The reversing valve is energized in cooling.
• If the Occupied Mode has been set, the ventilation fan will come on. This will stay
on continually.
• If pre-conditioning has been set to ON, outside air ventilation is disabled.
• The control logic allows the compressor speed to fluctuate normally unless the
relative humidity does not drop to the RH set-point in a reasonable amount of time.
This time is the Dehum Override Time set on Screen 7 (Timers and Counters) and
is adjustable.
• If, when the compressor is running full speed to satisfy humidity, the room is cooled
below the cooling set point and the relative humidity is still not satisfied, the com-
pressor continues to run at full cooling speed. Hot gas reheat (and electric reheat, if
chosen), is activated to keep from overcooling the room to an uncomfortable level.
