Microprocessor Controller for DOAS
23
Menu
e
conomizer
c
onTrol
v
ariables
.
The economizer screen appears when economizer function is enabled.
The outside air damper will modulate between the min and max position to
maintain the supply temperature set point.
The user can select the economizer control method from the following options:
Outside Dry Bulb
– Economizing is allowed when the outside dry bulb is less
than the economizer temperature enable set point.
Outside Enthalpy
- Economizing is allowed when outside enthalpy is less than
the economizer enthalpy set point.
Comparative Dry Bulb
- Economizing is allowed when outside temperature is
less than the space or return temperature.
Comparative Enthalpy
- Economizing is allowed when outside enthalpy is less
than the space or return enthalpy.
Maximum Position
– Each sequence that can adjust the OA damper set point
contains a max position to prevent excess OA. The active set point will be
determined based on the greatest demand of the configured sequences. For
example, if a unit is equipped with a DCV CO
2
and an economizer sequence,
the OA damper set point will react to an economizer demand even if the CO
2
set
point is satisfied. Likewise, if economizer is not available but CO
2
is above set
point, the OA damper will open to satisfy the CO
2
set point.
Economizer
– The active set point will be reset based on Economizer demand,
between the min and max positions.
Set Point Selections:
Constant Position
– The min OA percentage is constant; set by the controller.
SF Reset
– The min and max positions are reset by the supply fan speed.
BMS
– The BMS can directly control the OA damper position between the min ad
max percentages.
Building Pressure
– Damper position is reset by a building pressure control loop.
DCV CO
2
– Damper position is reset by a demand-controlled ventilation control
loop based on space CO
2
levels. The CO
2
max is the highest percentage that the
OA damper can modulate when solely based on CO
2
.
2 Position
– Damper position is reset to “2-Pos/Max Vent:” set point when a
contact closure is made. The 2-position damper operation can be configured to
temporarily force the unit into occupied mode until the contact is open
(Max Ventilation Mode - enabled in Advanced menu).
0-10 By Others
– The 0-10V signal directly correlates to the damper position
of 0-100%. When the signal is below the minimum damper position setpoint,
the damper will modulate to minimum position. When the signal is above the
maximum damper position setpoint, the damper will modulate to max position.
