Outdoor Temperature And Humidity Combination Sensor; Outdoor Temperature Sensor Failure Alarm; Outdoor Humidity Sensor Failure Alarm; Mixed Air Temperature Sensor - Bard MEGA-TEC W180B 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 C3-4.
6. Reference the Value to see the input of the sensor
(see Figure 51).
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 51
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 C3-
5.
6. Reference the Value to see the input of the sensor
(see Figure 52).
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 52
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 two mixed air temperature
sensors to monitor the mixed air temperature of each
air path separately. The mixed air is measured where
the economizers mix return air and outdoor air. This
measurement is used to determine if the economizer is
controlling correctly. These sensors are 10k ohm NTC
thermistors, located in the blower section.
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 C3-
15 (Mixed Air Temp 1) or C3-16 (Mixed Air Temp
2).
6. Reference the Value to see the input of the sensor
(see Figure 53 on page 34).
Manual 2100-749
Page 33 of 68