The Make Up Air Unit (MAU), also known as the Dedicated Outdoor Air System (DOAS) or 100% Outdoor Air system, presents four unique Modes of Operation.
Cooling Mode: Occupied Cooling is enabled when the temperature at the Mode Enable Sensor rises one deadband above the Cooling Setpoint.
Cooling is disabled when the mode enable temperature falls one deadband below the Cooling Setpoint.
(Note: MAUs are configured to use the outdoor air temperature as the mode enable sensor.)
In Cooling Mode, as the supply air temperature rises above the active Cooling Supply Air Temperature Setpoint, the compressors will stage on and modulate to maintain the active Supply Air Cooling Setpoint.
Cooling stages will continue to run until the supply air temperature falls below the active Supply Air Temperature Setpoint minus the cooling stage control window and the Cooling will begin to stage off.
Heating Mode: Common heating options are modulating gas, heat pump operation, and modulating SCR electric.
Occupied Heating is enabled when the temperature at the Mode Enable Sensor falls one deadband below the Heating Setpoint. Heating is disabled when the Mode Enable temperature raises one deadband above the Heating Setpoint.
In the Heating Mode, as the supply air temperature falls below the active Supply Air Heating Setpoint, the Heating will begin to stage on or to modulate.
Heating stages will continue to run until the supply air temperature rises above the active Supply Air Temperature Setpoint plus the heating stage control window at which point the Heating will begin to stage off.
Dehumidification Mode: Dehumidification is initiated when the outdoor air dewpoint rises above the Outdoor Air Dewpoint Setpoint by 2°F. The unit will leave the Dehumidification Mode when the dewpoint falls 2°F below this setpoint. The outdoor air dewpoint is calculated using the outdoor air temperature and the outdoor air humidity.
In the Dehumidification Mode, the compressors are controlled to maintain the Suction (Saturation) Temperature Setpoint, and Modulating Hot Gas Reheat is used to reheat the supply air. Reheat is controlled to the active Supply Air Setpoin.
Off Mode: System deactivated.
Each mode features specific control parameters; please see detailed operation sequences to ensure reliable performance and user satisfaction.
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