AHU capacity refers to the amount of air an Air Handling Unit (AHU) can condition and distribute within a building. It’s essentially a measure of the AHU’s ability to handle airflow. There are two main ways to express AHU capacity:
Airflow Rate: This is typically measured in Cubic Feet per Minute (CFM) or Cubic Meters per Hour (CMH). It represents the volume of air the AHU can move within a given timeframe. Higher CFM or CMH indicates a greater capacity to circulate air.
Cooling Capacity: This is measured in tons of refrigeration (TR) or kilowatts (kW) of cooling. It reflects the AHU’s ability to remove heat from the air it processes. A higher TR or kW rating signifies a greater capacity for cooling the conditioned air.
Choosing the right AHU capacity depends on several factors:
- Building size and layout: Larger buildings or those with complex layouts will require AHUs with higher airflow rates.
- Occupancy level: Buildings with more occupants will generate more heat, requiring AHUs with greater cooling capacity.
- Desired indoor temperature and humidity: Maintaining lower temperatures or more controlled humidity levels might necessitate a higher capacity AHU.
- Fresh air requirements: If a significant amount of fresh air needs to be introduced, the AHU will need sufficient capacity to handle that additional airflow.
Here are some additional points to consider regarding AHU capacity:
- Static pressure: This refers to the air pressure required to overcome resistance within the ductwork system. AHUs are also rated for their available static pressure, which should be sufficient to overcome the pressure drop in the specific duct system design.
- AHU selection process: Selecting the right AHU capacity involves careful calculations considering all the factors mentioned above. Consulting with an HVAC engineer is recommended to ensure you choose an AHU that meets your building’s specific needs efficiently.