Scholar V VAIVA Maintenance & Service Manual 10/2017 Rev.2
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• DI 0.3 –
CO2 Sensor
: Opens when the CO2 content of the room gets above set-
point of the sensor
• DI 0.4 –
Evaporator Coil Freeze-Stat:
Opens when temperature of the evaporator
coil fins falls below 28°F. This is an indication that the evaporator coil may be
freezing up.
B. Digital Outputs
• DO 0.0 – Provides 24 VAC ON signal for Electronic Expansion Valve and for
Variable Speed Compressor Driver Board
• DO 0.1 –
24 VAC to Reversing Valve:
Valve is energized in Cooling Mode.
• DO 0.2 –
24 VAC to Reheat Valve
: Valve is energized in the Dehumidification
Mode when the supply air temperature is below the cooling set-point
• DO 0.3 –
24 VAC to Condenser Fan Head Pressure Control
• DO 0.4 –
24 VAC to Heater Contactor
• DO 1.0 –
24 VAC to Indoor Blower Controller
• DO 1.1 –
24 VAC to Ventilation Control Relay
C. Analog Inputs
• AI 0 –
0-10 VDC modulating signal from indoor Relative Humidity Transmitter:
0 Volts = 0 %RH 10 volts = 100 %RH
• AI 1 –
2-10 VDC modulating signal from indoor Temperature Transmitter:
2 Volts = 50°F 10 volts = 150°F
D. Analog Outputs
• AO 0 –
0 – 20 ma current signal to Variable Speed Compressor driver board:
This signal is converted to voltage with a 500 ohm resistor at the board. The
voltage varies between 1 VDC and 9.4 VDC. 1 VDC drives the compressor at
1200 RPM. 9.4 VDC drives the compressor at 4800 RPM.
• AO1 –
0-20 ma current signal to EC Indoor Blower Motor control board:
This
signal is converted to voltage with a 500 ohm resistor at the board. The Indoor
Blower speed modulates linearly with the compressor speed. A maximum and
minimum blower speed can be set to correspond linearly with the maximum and
minimum compressor speeds.
E. Thermocouple Module
• Used to control defrost in heating mode.
• Used to control condenser fan cycling in cooling mode.
The Thermocouple Module has 4 channels. Type K thermocouples are used.
