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Scholar V VAIVA Maintenance & Service Manual 10/2017 Rev.2
Indoor air runs continuously
1. Indoor blower set to ON instead of Auto. This selection can be made on main screen.
2. Post -Purge timer allowing the blower to run for 90 seconds on off cycle.
ס This time period can be adjusted on the HMI screen. A user name and password
may be required.
Indoor air flow appears to be insufficient
1. The indoor air flow is automatically adjusted by the PLC to correspond with the
compressor speed. This allows the evaporator temperature to remain fairly constant.
2. When the compressor is running full speed,10 volts is sent by the PLC to the indoor
blower controller to set the speed. When the compressor is at minimum speed, 5 volts is
sent to the controller.
ס Check this voltage on the analog output resister on the PLC and on the speed con-
trol terminals of the indoor blower controller.
3. Check for dirty filters.
ס The ECM motors will automatically try to compensate to some extent for dirty filters,
but if filters are extremely dirty, the compensation is insufficient.
Unit cuts out on High Condenser Pressure (See Page 76)
1. This condition presents a message on the HMI screen.
ס A high pressure condition will reset automatically twice and then will lock out. A hard
lock out must be manually reset by pressing the Reset button on the main screen.
ס If the problem continues, the condenser blower(s) may be running improperly. On a
condenser system with dual blowers, one of the blowers is cycled on and off based
on the thermocouples embedded in the distributor tubes on the outdoor coils. See
the discussion of the HMI screens to change the settings on cycling the outdoor
fans for head pressure control.
Unit cuts out on Loss of Charge switch (See Page 76)
1. This condition presents a message on the HMI screen.
ס A significant loss of charge must be in play if this switch actuates.
ס Check the EEV and refrigerant sight glass as mentioned above to check for
symptoms of a refrigerant leak.
■ Be sure Schraeder caps are in place and are tight (Items 37 and 38).
■ Look for signs of refrigerant oil on components. This can often pinpoint a leak.
■ Use an electronic leak detector. Large leaks can sometimes be found with
soap bubbles.
Unit cuts out on High Discharge Temperature Switch (See Page 76)
1. This condition presents a message on the HMI screen.
ס A snap disc thermostat is located on the compressor discharge line (Item 5). This
switch opens an input to the PLC when the temperature reaches approximately
225°F.
ס If this condition occurs, press the Reset button on the main screen of the HMI.
■ If the problem persists, there could be a low refrigerant charge.
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This may be accompanied with a high superheat and the EEV opened
close to 100%.
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Low suction pressure may also be seen and can be read on the EEV
display (Screen #2)