Performance of VAV Fan Powered Terminal Units: An Evaluation of Operational Control Strategies for Series vs. Parallel Units

Previous papers under RP 1292 presented engineering models and experimental verification of those models for series and parallel VAV fan powered terminal units. Terminal units with 8 in. (203 mm) and 12 in. (304 mm) primary air inlets from three different manufacturers were evaluated under this research project. This paper presents the results from the research in terms of operational control strategies for series vs. parallel fan powered terminal units. Each system type was operated in a simulation that varied geographic location in five regions of the United States and under several different control strategies. Results show that, depending on system loads, system control, and operational settings, the VAV control strategy can have a significant impact on operations, comfort conditions, and energy consumption. Conventional control strategies are likely going to lead to underperforming systems and a resulting increase in energy consumption. Improvements to conventional control strategies are also presented and discussed in this paper.