How much larger should an air conditioning return duct be compared to the discharge duct?

The appropriate sizing of return air ducts compared to discharge ducts is critical for maintaining effective airflow and system efficiency in air conditioning systems. A return duct should generally be larger than the discharge duct to ensure that there is enough capacity to handle the volume of air being circulated back into the system.

Choosing to make the return duct 20% larger than the discharge duct is beneficial for several reasons. First, a larger return duct helps reduce the velocity of the returning air, which minimizes noise and turbulence. A lower velocity allows for a smoother flow of air back to the system, enhancing the overall performance of the air conditioner. Additionally, this sizing approach mitigates the risk of creating negative pressure in the space that might lead to inadequate air distribution or even damage to the system components due to improper airflow dynamics.

Ultimately, this practice aims to achieve a balance whereby the system operates at maximum efficiency, providing optimal comfort levels while prolonging the life of the equipment.