88
Economizer
Economizer type sets the type of economizer logic that will be used. This feature will control the
economizer using a
0-10V DC
signal output on the MUA board. The table below shows option selections
and definitions.
Use the HMI to select Economizer type. Go to
Factory Settings > Unit Options > Outdoor Air Config >
Economizer
.
Disable Cooling
Figure 41 - Damper Assembly
This allows the user to set the Outdoor Air (OA) percentage
through the damper assembly (
) when mechanical
cooling is disabled.
Refer to
“Psychrometric Chart” on page 89
for economizer
operation and logic.
Table 15 - Economizer Options
Option
Definition
Fixed Dry Bulb
The economizer will modulate open if the outdoor air temperature is less than
the economizer temperature set point. The modulation occurs from the current
damper position to fully open over a specific temperature range (determined by
the economizer temperature band value).
Differential Dry Bulb
The economizer will modulate open if the outdoor air temperature is less than
the return air temperature. The modulation occurs from the current damper
position to fully open over a specific temperature range (determined by the
economizer temperature band value).
Fixed Total
The economizer will modulate open from the current position if the outdoor air
dew point temperature is less than the economizer dew point set point, and the
outdoor dry bulb temperature is less than the economizer temperature set
point. The dew point set point is calculated using the economizer temperature
and humidity set points. The modulation occurs from the current damper
position to fully open over a specific dew point temperature band.
Differential Total
The economizer will modulate open from the current position if the outdoor air
wet bulb temperature is less than the economizer dew point set point, and the
outdoor dry bulb temperature is less than the economizer temperature set
point. If the return dew point is less than the dew point set point, the unit will
use the return dew point as the beginning of the modulation band. The
modulation occurs from the current damper position to fully open over a specific
dew point temperature band.
