Outdoor Temperature And Humidity Combination Sensor; Outdoor Temperature Sensor Failure Alarm; Outdoor Humidity Sensor Failure Alarm; Mixed Air Temperature Sensor - Bard MEGA-TEC W090A Service Instructions Manual

Outdoor Temperature and Humidity Combination Sensor

The unit is equipped with a combination outdoor
temperature and humidity sensor to monitor
outdoor conditions for the economizer operation.
The temperature is measured with a 10k ohm NTC
thermistor. The humidity is measured with a humidity
sensor that outputs a 4-20mA signal to the controller.
The outdoor temperature can be verified by:
1. Press MENU key to go to the Main Menu screen.
2. Press UP or DOWN keys and ENTER key to enter
TECHNICIAN password 1313.
3. Press UP or DOWN keys to scroll to I/O Config;
press ENTER key.
4. Press UP or DOWN keys to scroll to Analog Inputs;
press ENTER key.
5. Press UP or DOWN keys to scroll to Analog Ins
4/19.
6. Reference the Value to see the input of the sensor
(see Figure 39).
7. To apply an offset, press ENTER key to scroll to
Offset.
8. Press UP or DOWN keys to change to the desired
value.
9. Press ENTER key to save the value.
FIGURE 39
Outdoor Temperature Sensor
The outdoor humidity can be verified by:
1. Press MENU key to go to the Main Menu screen.
2. Press UP or DOWN keys and ENTER key to enter
TECHNICIAN password 1313.
3. Press UP or DOWN keys to scroll to I/O Config;
press ENTER key.
4. Press UP or DOWN keys to scroll to Analog Inputs;
press ENTER key.
5. Press UP or DOWN keys to scroll to Analog Ins
5/19.
6. Reference the Value to see the input of the sensor
(see Figure 40).
7. To apply an offset, press ENTER key to scroll to
Offset.
8. Press UP or DOWN keys to change to the desired
value.
9. Press ENTER key to save the value.
FIGURE 40
Outdoor Humidity Sensor

Outdoor Temperature Sensor Failure Alarm

When the sensor reads a value that is outside of the
acceptable -41 to 303.0° range, an alarm will be
generated indicating the sensor has failed. This alarm
condition will disable the economizer.
This alarm is fixed and cannot be adjusted.

Outdoor Humidity Sensor Failure Alarm

When the sensor reads a value that is outside of the
acceptable 0 to 100% RH range, an alarm will be
generated indicating the sensor has failed. This alarm
condition will disable the economizer when the mode is
set to temperature and humidity or enthalpy.
This alarm is fixed and cannot be adjusted.

Mixed Air Temperature Sensor

The unit is equipped with a mixed air temperature
sensor to monitor the mixed air temperature. The
mixed air is measured where the economizer mixes
return air and outdoor air. This measurement is used
to determine if the economizer is controlling correctly.
The sensor is a 10k ohm NTC Thermistor.
The mixed air temperature can be verified by:
1. Press MENU key to go to the Main Menu screen.
2. Press UP or DOWN keys and ENTER key to enter
TECHNICIAN password 1313.
3. Press UP or DOWN keys to scroll to I/O Config;
press ENTER key.
4. Press UP or DOWN keys to scroll to Analog Inputs;
press ENTER key.
5. Press UP or DOWN keys to scroll to Analog Ins
18/19.
6. Reference the Value to see the input of the sensor
(see Figure 41 on page 30).
Manual 2100-671C
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