DUCT SIZE CALCULATOR
What size rigid duct do I need for my air system?
To determine the appropriate size of rigid duct for your air system, follow these steps:
Enter the required air flow rate: Determine the amount of air that needs to be moved through the system, typically measured in litres per second (L/s)
Enter the estimated air temperature: Air temperature affects air density, which in turn affects the airflow. Consider the temperature at which the system will operate
Enter the estimated relative humidity of the air: Relative humidity also affects air density. Take into account the humidity levels expected in the air stream
Enter the limit of linear pressure loss in your system: Specify the acceptable pressure drop in the ductwork. As a general guideline, a range of 0.8-1 Pascal per meter (Pa/m) is considered optimal
Enter one side of rectangular duct or one axis of oval duct: If you're using a rectangular duct, enter the measurement of one side. For an oval duct, enter the minor or major axis
Check the resulting air velocity, he recommended supply air velocity typically ranges between 4 to 6 m/s for most HVAC systems. This range ensures adequate air distribution without causing discomfort or noise issues
The calculator will provide the minimum required dimension for the other side of the rectangular duct, other axis of the oval duct, and the equivalent diameter for a round duct. Keep in mind that these results are based on minimum dimensions. In practical terms, round the dimensions to the nearest size available from your duct manufacturer.
Note: NCC Section J ductwork fan system DtS requirement: The pressure drop in the index run across all straight sections of rigid ductwork and all sections of flexible ductwork must not exceed 1 Pa/m when averaged over the entire length of straight rigid duct and flexible duct. The pressure drop of flexible ductwork sections may be calculated as if the flexible ductwork is laid straight.
Disclaimer- Our engineering calculators only provide guidance and estimate to help you determine your component size requirements. This guide should not be considered a replacement for an expert advice. If you have any questions regarding TPCE calculators, please feel free to CONTACT US today, one of our friendly experts will be in touch with you as soon as possible to assist you with your engineering needs.