A damper in an Air Handling Unit (AHU) is a valve or plate that regulates airflow within the system. Specifically, it's used to control the amount of:
- Outdoor air entering the AHU.
- Air exhausted from the system.
- Return air from the building recirculated through the system.
Essentially, dampers act as adjustable barriers within the AHU's ductwork. They can be opened or closed to varying degrees to adjust airflow rates and mix different air streams (outdoor, exhaust, and return). This control is crucial for maintaining proper ventilation, temperature, and air quality within a building.
Here's a breakdown of the functions and types of dampers in AHUs:
Functions of Dampers in AHUs:
- Airflow Control: The primary function is to regulate the volume of air moving through different sections of the AHU.
- Mixing Air: Dampers allow for the mixing of outdoor air (fresh air), return air (air recirculated from the building), and sometimes exhaust air (air being expelled from the building). This mixing helps to optimize energy efficiency and maintain indoor air quality.
- Balancing Air Pressure: Dampers help balance the air pressure within the AHU and the connected ductwork, ensuring even airflow distribution throughout the building.
- Zone Control: In some AHU systems, dampers are used to control airflow to specific zones or areas within a building, allowing for independent temperature and ventilation control.
- Isolation: Dampers can completely shut off airflow to certain sections of the AHU for maintenance or repair purposes.
- Preventing Backdraft: Some dampers, known as backdraft dampers, prevent reverse airflow in the ductwork, especially in exhaust systems.
- Fire Safety: Fire dampers are installed to close automatically in the event of a fire, preventing the spread of flames and smoke through the ductwork.
Types of Dampers Used in AHUs:
| Damper Type | Description | Application |
|---|---|---|
| Parallel Blade | Blades rotate in the same direction, offering less linear airflow control. | On/off applications and when precise airflow modulation is not critical. |
| Opposed Blade | Blades rotate in opposite directions, providing more linear and precise airflow control. | Applications requiring accurate airflow modulation, such as mixing boxes, variable air volume (VAV) boxes, and precise zone temperature control. |
| Round Dampers | Circular dampers used in round ductwork. | Round duct systems. |
| Backdraft Dampers | Allow airflow in only one direction, preventing reverse airflow. | Exhaust systems and applications where preventing backflow is crucial. |
| Fire Dampers | Automatically close in the event of a fire to prevent the spread of flames and smoke. | Ductwork passing through fire-rated walls or floors. |
| Motorized Dampers | Controlled by an electric or pneumatic actuator, allowing for automated airflow adjustment. | Automated control systems and applications requiring remote adjustment of airflow. |
| Manual Dampers | Adjusted manually using a lever or handle. | Simple applications where infrequent adjustment is needed. |
| Balancing Dampers | Used to adjust airflow to balance the HVAC system. | Balancing airflow to different zones in a building. |
Dampers are essential components in AHUs that enable precise control over airflow, ensuring efficient and effective HVAC system operation. Their proper functioning is critical for maintaining comfortable and healthy indoor environments.
