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Marvair 8AA1024A-1060A & 8AA2036A-2060A I&O Manual
03/2021 Rev.1
1.8 Economizer Components (Economizer Equipped Models Only)
Damper Actuator:
The damper actuator is a 24V motor that modulates the position of the damper blade. It is capable
of driving a full 90 degrees within 90 seconds. The assembly has a spring return to close the damper
during power outage.
Economizer changeover control (W1 Jumper)
The economizer can be controlled by either an enthalpy sensor or a dry bulb sensor. 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 free cooling). If the outdoor ambient is too hot or humid
(enthalpy sensor only), 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.
During the testing of the air conditioner at the factory, the control board has been configured for the
sensor in the air conditioner. There should be no need to change the sensor configuration. If an enthalpy
sensor is being used, pins 1 & 2 should be jumpered on the board. If a dry bulb sensor is being used,
pins 2 & 3 should be jumpered. See item 1 in Figure 4 for the location of this jumper.
Economizer changeover control setting - Enthalpy Sensor
The enthalpy sensor responds to the total heat content of the outdoor air to provide the changeover
to outside air for free cooling. The control board must be configured for proper operation of the
economizer by selecting the desired changeover temperature. The desired temperature is selected
by four DIP switches on the board. See item 9 in Figure 4 for the location of the DIP switches.
1. Selecting the set point for the enthalpy sensor. On the board there are four DIP switches – 1, 2,
3 & 4 - that determine the ambient temperature at which the economizer damper opens. These
DIP switches correspond to the following temperatures:
DIP Switch #
Previous Honeywell controller setting
Temperature °F/°C
All 4 Switches Down
A
73°/23.8°C
1
A
73°/23.8°C
2
B
70°F/21.1°C
3
C
67°F/19.4°C
4
D
63°F/17.2°C
2. Gently push the DIP switch UP to select the desired set point temperature. The factory setting is
for DIP switches number 1, 2, & 3 to be in the Down position and #4 to be in the Up position.
With DIP switch #4 in the Up position, the economizer damper will begin to open when the
ambient temperature is 63°F/17.2°C.
3. Only one switch should be in the Up position.
Note: having all four switches in the down position is the same setting as having the #1 switch
in the Up position.
DANGER
Sever hazard. The economizer contains moving parts capable of causing
serious injury or death. Disconnect power before removing the covering panel.
Economizer changeover control – Dry Bulb Sensor
The dry bulb sensor only responds to the dry bulb temperature of the outside air and ignores the humidity.
The sensor has eight set points. The factory setting is 58°F (14.5°C). These set points can be changed
by moving the DIP switches on the top of the dry bulb sensor. See Fig. 2.
