Economizer Operation - Minimum Position; Miscellaneous Components; Supply Temperature Sensor; Supply Temperature Sensor Failure Alarm - Bard MEGA-TEC W090A Service Instructions Manual

When the economizer is activated during a free cooling
call only, using any of the previously mentioned modes,
a 0-10v analog signal will be sent to the economizer
actuator. The actuator will then open and close the
damper blades to maintain a mixed air temperature of
55°F. When the mixed air temperature increases, the
damper will open and when the mixed air temperature
decreases, the damper will close.
The economizer may be disabled by the LC if the
system determines it needs to enter dehumidification
mode. More information about the dehumidification
sequence can be found in the latest revision of LC6000
Service Instructions 2100-669. In addition to dehum
mode, the economizer may be disabled for 5 minutes
(adjustable) if the dust sensor indicates the outdoor
air may cause particulate buildup in the air filters.
After the time has expired and on a call for cooling,
the economizer will open again to sample the air. The
wall-mount unit will either return to normal operation
or remain locked out for another 5 minutes.
Economizer Operation – Minimum Position
The economizer has an option to set minimum position
for the economizer. The minimum position will only
be active while the blower is operating. To enable
minimum position all the time, continuous blower must
be activated for the wall unit in the LC6000. See latest
version of LC6000 Service Instructions 2100-669 for
continuous blower configuration.
To set the minimum position value:
1. Press MENU key to go to the Main Menu screen.
2. Press UP or DOWN keys and ENTER key to enter
USER password 2000.
3. Press UP or DOWN keys to scroll to System Config;
press ENTER key.
4. Press UP or DOWN keys to scroll to Economizer
Setup A2.
5. Press ENTER key to scroll to Min Position (see
Figure 42 on page 30).
6. Press UP or DOWN keys to change to the desired
value.

Miscellaneous Components

Supply Temperature Sensor

The unit is equipped with a supply air temperature
sensor to monitor the leaving air temperature of the
unit. The temperature is measured with a 10k ohm
NTC thermistor.
The supply 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.
Manual 2100-671C
Page 32 of 59
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
2/19.
6. Reference the Value to see the input of the sensor
(see Figure 46).
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 46
Supply Air Temperature Sensor

Supply Temperature Sensor Failure Alarm

When the sensor reads a value that is outside of the
acceptable -41.0 to 303.0° range, an alarm will be
generated indicating the sensor has failed.
This alarm is fixed and cannot be adjusted.

Emergency Cooling Mode

If the shelter temperature is above the high temperature
alarm setpoint on the LC, the unit will be commanded
into emergency cooling mode. In this mode, the
unit will operate the economizer regardless of the
economizer setup, as long as the outdoor temperature is
below the indoor temperature. This will stay active until
the LC returns the unit to normal operation.
Emergency Cooling − Orphan Mode
When the unit is not connected to the LC6000 and
operating in orphan mode, the unit still has the
capability to operate in emergency cooling mode. By
default this feature is not enabled.
To enable emergency cooling in orphan mode:
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 Adv System
Config; press ENTER key.
4. Press UP or DOWN keys to scroll to Emer. Cool B6.