In HVAC (Heating, Ventilation, and Air Conditioning) systems, risers and plenums are important components that play different roles. While they are both used to distribute air throughout a building, they have distinct differences in terms of their design and function. In this answer, we will discuss the differences between risers and plenums.
Risers:
A riser is a vertical duct that connects a HVAC system’s air handling unit (AHU) to the floor vents or diffusers. Risers are used to distribute conditioned air from the AHU to various floors of a building. They are typically made of metal or fiberglass and are available in various sizes depending on the volume of air that needs to be circulated.
Plenums:
A plenum is a compartment or chamber that serves as a central distribution point for conditioned air in an HVAC system. It is typically located above a dropped ceiling or below a raised floor and is connected to the air handling unit via a main duct. The plenum distributes air to various branch ducts that, in turn, supply air to individual rooms or spaces. Plenums can be made of various materials, including sheet metal or fiberglass, and can be rectangular or circular in shape.
Differences between Risers and Plenums:
- Function: The primary function of a riser is to distribute air from the AHU to floor vents or diffusers. On the other hand, the primary function of a plenum is to serve as a central distribution point for conditioned air in an HVAC system.
- Location: Risers are typically located within the building’s walls and run vertically to supply air to various floors. In contrast, plenums are typically located above dropped ceilings or below raised floors.
- Shape and Size: Risers are typically cylindrical or rectangular in shape and are available in various sizes depending on the volume of air that needs to be circulated. Plenums, on the other hand, can be rectangular or circular in shape and are usually larger in size than risers.
- Material: Risers are usually made of metal or fiberglass, while plenums can be made of various materials, including sheet metal or fiberglass.
- Airflow: Risers have a higher air velocity than plenums, as they are designed to distribute air to individual floors. Plenums, on the other hand, have a lower air velocity, as they are designed to distribute air to individual rooms or spaces.
Conclusion:
In summary, risers and plenums are both essential components of an HVAC system, but they have distinct differences in terms of their design and function. Risers are used to distribute air from the AHU to floor vents or diffusers, while plenums serve as a central distribution point for conditioned air in an HVAC system. Understanding the differences between these components can help HVAC professionals design and install effective and efficient HVAC systems.