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Marvair MGA3090-3180 Wall Mount AC I&O Manual 05/2023 Rev.14
Enthalpy Setpoint is Setting 14 in control
board configuration menu.
Options
A=
73ºF
B=
70ºF
C=
67ºF
D=
63ºF
E=
55ºF
All settings are @ 50%Rh
Figure 3. Enthalpy Sensor & Temperature Control Points
Enthalpy Operation
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. The Supply Air sensor monitors the supply
air of the system in economizer mode to modulate the economizer damper to maintain a 55F
supply air temperature.
During the testing of the air conditioner at the factory, the control board has been configured for
the sensor type used in the system. There should be no need to change the sensor configuration.
If an enthalpy sensor is being used, setting 13 of the control board configuration menu will be
set for EN= Enthalpy. A disconnected or faulty enthalpy sensor is annunciated on the control
board display as “ES-F”. Economizer operation is only allowed in Cooling Mode.
Note:
A call for Y2 or FC Inputs or a faulty or disconnected enthalpy sensor will override the
economizer operation and force the compressor to operate.
3.2 Dry Bulb Sensor and Operation –
The dry bulb sensor only responds to the dry bulb temperature
of the outside air and ignores the humidity. The sensor is a 10K NTC sensor probe. The factory
setting is 63°F. This setpoint can be adjusted in 1F increments from 20F to 105F in the control
board configuration menu setting 14. Example of the dry bulb sensor is shown below.
Note:
Selecting N=No in configuration setting 12 will disable economizer operation.
