Improving Control of a Dual-Duct Single-Fan Variable Air Volume Systems

Abstract

This paper discusses improved control strategies for dual-duct single-fan variable air volume (VAV) systems. Common control strategy for supply air volume modulation is evaluated, and an improved air volume control strategy that maintains separate cold and hot air duct static pressure set points is presented. The paper also explores the interactions between the cold and hot deck temperatures and duct static pressures, and discusses the impact of non-ideal deck temperature settings on duct static pressures and overall system energy consumption. To compensate the negative impact of non-ideal cold and hot deck temperature set points, the authors propose using real-time duct static pressure readings as feedback signals to fine-tune the deck temperature set points. These new control schemes can reduce simultaneous cooling and heating while reducing fan power consumption.