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Marvair 8AA1024A-1060A & 8AA2036A-2060A I&O Manual
03/2021 Rev.1
Equipment, devices and necessary system components are specified in the respective section.
Note:
1. All inputs on the Controller go through a 5 seconds Time-On Delay to prevent nuisance request.
Compressor Outputs go through 5 seconds staggered Time On delay to prevent nuisance tripping
of breaker due to the inrush associated with these large inductive loads.
2. Normal Operating Mode describes a mode in which there are no active faults which would inter-
rupt the operation of the system.
3. A control voltage being “High” describes the event in which 24VAC is supplied to that input.
Conversely, a “Low” control signal describes an event in which less than 5VAC is supplied to the
1.0 – Blower Operation
A request for Fan Only (independent G-signal via Digital input or MODBUS), results in the indoor motor
turning “ON” and operating at the “Y2” motor speed (Only Applicable for EC motors). See Installation/
Operation manual to see how to set the speeds for the various operations. As long as there is a request
for Fan (G-input High or a request for Indoor Fan Only via MODBUS), the indoor motor will continue
to operate at the Y2 speed setpoint.
When there is a request for Indoor Fan (G-input High) along with a request for cooling, heating or
dehumidification, the G-Input becomes lowest priority. This means that in any combination involving
the G-input, the speed associated to Fan Only will never take precedence.
The priority list from Highest to Lowest goes as follows:
1. Stage 2 Cooling Request (Y2-Input)
2. Stage 1 Cooling Request (Y1-Input)
3. Electric Heat Request (W2-Input)
4. Dehumidification Request (Hum-Input)
5. Indoor Fan Request (G-Input)
Note
– The priority list above also describes the operation that takes precedence in the event that there
is a request for all operations or a combination of operations. The controller will NOT energize the
compressor outputs and the heater output simultaneously.
The speed at which the Indoor Fan Operates during Stage 1 (Y1) and Stage 2 (Y2) Cooling Request
can be set directly at the board using the jumper associated to the “Y1” and “Y2” pin. All other requests
run at 80% of Y2 speed except for the lone G-input which runs at the Y2 speed settings. All requests
are interlocked with the Indoor Fan and will run the Fan at the respective speed associated with the
operation. This means that a lone call for Stage 1 (Y1) Cooling will automatically run the Indoor Fan
at Stage 1 (Y1) Cooling Speed even without a request for Indoor Fan. This holds true for all request.
2.0 – Cooling Operation
2.1– Mechanical Cooling
This section will describe the sequence of operation which takes place during Direct Expansion (DX)
cooling from a control standpoint.
2.1.1
Y1 Cooling (Partial Capacity 50-60%)
In normal operating mode, a request for “Stage 1 Cooling (Y-input)” via MODBUS, Digital Input
or Onboard Thermostat, energizes Compressor 1 Relay Output (CC1) on the PCB. The controller
provides a continuous control signal associated to the Indoor Fan Motor, that is proportional to the
“Y1” speed setting on the board or via MODBUS. It also outputs a request dependent (based on
FCC IN) control signal for the Outdoor Fan Motor. In Stage 1 Cooling operation, the compressor
