9
Marvair GAA A/C w/Gas Heat I&O Manual
06/2023 Rev.5
Configuration “E”: Two-Position Motorized Fresh Air Damper w/Pressure Relief Ventilation &
Independent Control
Control Board/Factory Installed Relay Logic:
The 92589 control board allows the position of the “E”
damper to be set for desired outside air intake from fully closed to fully open. Setting 15 of the control
board configuration menu allows the user to set the position from 20 (2VDC / Closed) to 100 (10VDC
100% open). The damper position can be adjusted in 1VDC increments to any position from closed to
100% open as required.
Operation:
Upon a “Call for Motorized damper” via a 24V signal from an external user-installed device,
the motorized damper opens to the position selected in the control board configuration menu setting 15
and the indoor blower operates. A 24VAC signal {sourced from LVTB 24VAC “R” and supplied through
a user-provided Normally Open (NO) contact} activates (opens) the Motorized Damper and connected
Relief Damper. When the 24VAC signal is removed, the motorized damper spring returns to the fully
closed position and the indoor blower stops operation. The motorized damper Does NOT open when
there is a call for the indoor fan (G).
Note:
This circuit does not interrupt the compressor or heater operation.
Configuration “F”: No Free Cooling, 100%- Damper Opening, Emergency Ventilation Only w/
Pressure Relief and Independent Control
Factory Installed Relay Logic:
Upon a “Call for emergency ventilation”, from an external user-provided
device; the motorized damper opens to 100% open position and the indoor blower is forced to operate.
During “Emergency Ventilation mode”, the compressor and heater do not operate. The relay has a wire
lead extended for the installer to connect their emergency ventilation control signal.
Note:
This circuit interrupts the compressor and heater operation and forces the indoor blower and damper
to operate during emergency ventilation mode.
Configuration “N”: Manual Fresh Air Damper (Standard)
Barometric damper capable of up to 15% of the air conditioner’s total rated airflow of outside air; field
adjustable, no pressure relief.
1.7 Economizer Operation – Cooling Cycle (Marvair GAA unit with Economizer only)
The economizer is a regulated damper system with controls. The damper regulates the circulation of outside
air into the enclosure ( when the outdoor air conditions are suitable ) to reduce the need for mechanical
cooling, save energy, and extend compressor life.
Depending upon the options selected, the damper responds to either enthalpy or dry bulb temperature of
the outdoor air. On a call for cooling from a space thermostat, it operates as follows:
When the enthalpy of the outdoor air is below the set point, the outdoor air damper is proportioned open
( and return air damper is proportioned closed ) to maintain between 50
o
F and 56
o
F at the mixed / discharge
air sensor.
When the enthalpy of the outdoor air is above the set point, the outdoor air damper closes to its minimum
position. A call for cooling from the space thermostat brings on mechanical cooling.
An optional built-in adjustable minimum position potentiometer, p / n 70012, controls the amount of
outdoor air admitted to meet minimum ventilation requirements.
