What is the maximum face velocity for return air grilles in non-engineered systems?

In non-engineered systems, the maximum face velocity for return air grilles is established at 450 feet per minute. This specification is in place primarily to ensure efficient airflow while minimizing noise levels within the HVAC system. Higher velocities can lead to increased sound levels, which may result in discomfort for occupants in the space.

The choice of 450 feet per minute strikes a balance that adequately allows for effective air return without causing obstruction or excessive turbulence, which can diminish the system's performance. Additionally, staying within this limit helps to prevent issues related to wear and tear on equipment, improves system longevity, and allows for better air quality in living or working environments. Understanding these parameters is essential for proper design and implementation of HVAC systems in compliance with the code.