Where is the outside air piped into a residential system?

In a residential HVAC system, outside air is typically introduced at the return air plenum. This location is critical because the return air plenum is responsible for gathering air from various parts of the home and circulating it back to the heating or cooling system. By introducing outside air at this point, it can mix with the indoor air, thereby improving indoor air quality and ensuring that the system efficiently processes that air for heating or cooling before it is distributed back into the living spaces.

Additionally, bringing in outside air at the return air plenum helps to balance the air pressures within the home, preventing negative pressure conditions that might lead to drafts or increased energy consumption. This design is essential for maintaining comfort and energy efficiency in residential systems.

While the supply plenum, furnace, and air conditioner play vital roles in the HVAC system, they are not designed for the direct introduction of outside air, which is crucial for maintaining air quality and effective system operation.