In many VAV systems, the exterior zones will utilize fan-powered terminal units. When compared to a single duct terminal unit, the fan-powered versions have a fan that enables the induction of plenum air into the airflow. During heating, the supplied conditioned air can be reduced to the minimum ventilation rate and the heating airflow is supplemented by induced plenum air. The introduction of the fan adds a few more variables to consider when selecting the equipment.
Parallel vs. Series
Before selecting the individual terminal units,...