What is the flow restriction for return air from any room according to the code?

The flow restriction for return air from any room is established to ensure balanced airflow within the HVAC system, which is crucial for maintaining indoor air quality and energy efficiency. Choosing an option where the flow of return air is less than that of supply air helps prevent the development of negative pressure in the conditioned space.

When return airflow is lower than supply airflow, it encourages proper mixing of air, allowing the HVAC system to operate efficiently while maintaining comfortable temperatures. Additionally, this setup reduces the risk of issues such as drafts and temperature imbalances, which can occur if too much air is drawn from a room.

On the other hand, if the return airflow were greater than the supply, or equal to outside air, it could lead to several potential problems, such as inadequate conditioning of the space, increased energy use, and uncomfortable living conditions. Therefore, maintaining a flow restriction where return air is less than supply air is an essential guideline by the code for optimal system performance.