23
Demand Controlled Ventilation (DCV)
If a field-installed CO
2
sensor is connected to the EconoMi$er X
control, a Demand Controlled Ventilation strategy will operate
automatically. As the CO
2
level in the space increases above the
setpoint (on the EconoMi$er X controller), the minimum position
of the dampers will be increased proportionally, until the
Maximum Ventilation setting is reached. As the space CO
2
level
decreases because of the increase in fresh air, the outdoor damper
will follow the higher demand condition from the DCV mode or
from the free cooling mode.
DCV operation is available in Occupied and Unoccupied periods
with EconoMi$er X Controller. However, a control modification
will be required on the units to implement the Unoccupied period
function.
TROUBLESHOOTING
For a list of common operating issues and concerns see Table 14.
Power Loss (Outage or Brownout)
All setpoints and advanced settings are restored after any power
loss or interruption, as all settings are stored in the Economizer
controller’s non-volatile flash memory.
NOTE: If the power goes below 18 Vac, the W7220 controller
module assumes a power loss and the 5 minute power up delay
will become functional when power returns above 18 Vac.
Alarms
The economizer module provides alarm messages that display on
the 2-line LCD.
NOTE: Upon power up, the module waits several seconds before
checking for alarms. This allows time for all the configured
devices (e.g., sensors, actuator) to become operational.
If one or more alarms are present and there has been no keypad
activity for at least 5 minutes, the Alarms menu displays and
cycles through the active alarms.
The Alarms menus can be navigated to at any time. See Table 6
for the Alarms menu.
Clearing Alarms
Once the alarm has been identified and the cause has been
removed (e.g., replaced faulty sensor) the alarm can be cleared
from the display.
To clear an alarm, perform the following:
1. Navigate to the desired alarm.
2. Press the
button.
3. ERASE? displays.
4. Press the
button.
5. ALARM ERASED displays.
6. Press the
(Menu Up) button to complete the action and
return to the previous menu.
NOTE: If the alarm still exists after it is cleared, it is redisplayed
within 5 seconds.
Table 14 —
Operating Issues and Concerns
ISSUE OR CONCERN
POSSIBLE CAUSE AND REMEDY
My outdoor temperature reading on the
STATUS menu is not accurate
Check the sensor wiring:
• Enthalpy sensors are to be wired to the S-Bus terminals.
• Temperature sensors are to be wired to the OAT and MAT terminals.
If my enthalpy sensor drifts in accuracy over time, can I re-
calibrate it?
The sensor is not able to be re-calibrated in the field. However there is a menu item
under the ADVANCED menu to input a limited off set in temperature and humidity for
each sensor connected to the economizer.
Can I go back to factory defaults and start over?
Under the SYSTEM SETUP menu you can change the setpoints to the factory
defaults.
Will I be able to see the LCD screen when it is in the unit?
The LCD screen has a backlight that is always illuminated.
What is a good setpoint for the Mixed Air
Temperature (MAT)?
The mixed are temperature is the temperature of air that you want to supply to the
space. In a commercial building, this is between 50°F and 55°F (10°C and 13°C). The
mixed air is the mixing of the return air and the outdoor air.
I am using enthalpy sensors. Why did the control ask me to
input a dry bulb changeover temperature?
In the even the humidity sensor in the enthalpy sensors fails, the backup algorithm in
the control is to default to the temperature sensor in the enthalpy sensor.
In checkout, the outdoor damper closes when I command it
to open.
Check the actuator linkage or rotation. In the CHECKOUT mode, the outdoor damper
should drive open or closed with the return air damper having the opposite effect.
How do I set my minimum position?
The minimum position is set using the VENTMIN and VENTMAX setup in the
SETPOINTS menu. VENTMIN is the minimum ventilation required when using an
occupancy sensor and VENTMAX is the minimum ventilation when not using an
occupancy sensor for Demand Controlled Ventilation. The VENTMAX position is set
the same as with the potentiometer on the analog economizers and is the output
voltage to the damper actuator. The range is 2 Vdc closed OA damper and 10 Vdc
open OA damper.
What if my damper does not go completely closed in the
checkout operation?
Check the damper linkage or hub to make sure the damper is able to close
completely.
How do I set the OCC?
There are two settings for the OCC setting: INPUT and ALWAYS. INPUT is from the
space thermostat, if it has an occupancy output. ALWAYS is the unit in the occupied
mode, if the economizer is powered (fan on).
Does the economizer save my program values if the unit
loses power?
Yes, once the changes are stored in the controller they will be stored until they are
changed by the operator.
If the unit is left in checkout, how long will the unit stay in
checkout mode without input?
The unit will remain in checkout for 10 minutes, then return to normal operation.
