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Eubank 7AA1024H-1060H & 7AA2024H-2060H I&O Manual 03/2021 Rev.1
Controls
The economizer is controlled by an enthalpy sensor or optional dry bulb sensor.
Economizer Changeover Control
The enthalpy sensor responds to the total heat content of the outdoor air to provide changeover to outside
air for free cooling. The change point is adjustable from 63°F @ 50% RH (full clockwise) to 73°F @
50% RH (full counterclockwise). Refer to Figure 3.
Once the enthalpy sensor has selected outside air, the mixed air sensor will limit the air temperature
delivered to the space by modulating the damper blade to "mix in" a quantity of inside air to provide a
constant 50° to 63°F. (Adjustable minimum potentiometer is optional.)
The sensor modulates the position of the outside air damper in response to input from the enthalpy and
mixed air sensors. The controller is designed to maintain the supply air temperature between 50
o
to 56
o
F
by mixing warm indoor air with cooler outdoor air.
On a call for cooling from the wall-mounted thermostat, if outdoor conditions are suitable, the sensor will
open the damper and admit outside air (i.e., economizer cooling). If the outdoor ambient is too hot or
humid, the sensor will place the actuator in the closed or minimum open position and activate mechanical
cooling. The compressor is locked out during the economizer cooling mode.
Figure 2 - Enthalpy Sensor Temperature Control Points
Mixed Air Sensor
The mixed air sensor is a thermistor mounted on a bracket adjacent to the right side of the blower
assembly. The thermistor senses the air temperature entering the structure, and provides a signal to the
economizer controller for modulating the position of the damper. Nominal resistance of the sensor at
77°F is 3000 ohms.
