VAV systems are the most common HVAC system for commercial buildings but duct design practices vary widely around the country. Duct design practices are seldom based on hard analysis of whether they are optimum from a life cycle cost perspective. This seminar compares various VAV box inlet and outlet duct design options including their impact on first costs and pressure drop. The presentation focuses on single duct VAV reheat systems, but most of the principles apply to other VAV system variations, such as dual duct and fan-powered box systems.

There is a perception that a reverse-return hydronic piping configuration uses more piping and is therefore more expensive than its direct-return counterpart. While the cost disadvantage of reverse-return is true in some instances, this seminar presents a case that reverse-return doesn’t always add piping length and system cost, depending on system configuration. Reverse-return is sometimes overlooked or dismissed out-of-hand when it offers tangible benefits and could easily have been implemented at no net cost to the project, so a goal of this seminar is to encourage pipe system designers to explore and consider reverse-return in further detail.

ASHRAE 90.1-2013 specifies that “Water economizer systems shall be capable of cooling supply air by indirect evaporation and providing up to 100% of the expected system cooling load at outdoor air temperatures of 50°F dry bulb/45°F wet bulb and below.” Many engineers size the components involved in the economizer (cooling tower, cooling coils and ductwork or piping serving constant load spaces) solely for their primary function without considering how these components affect the ability to meet the above requirement. This presentation discusses whether the above requirement can be met and what are the implications for selection of the components.

Many large central chilled water systems depend on high chilled water temperature differential, ΔT, to minimize pumping energy and optimize chilled water thermal storage capacity. Buildings directly connected to central chilled water distribution systems should be designed to minimize pumping energy and maximize return chilled water return temperature to the central plant. High ΔT is achieved with proper coil and control valve selection, piping and pumping design and supply water control. This seminar presents ways to improve performance and avoid problems commonly encountered in large chilled water systems.