This paper discusses how dual-duct variable-air-volume systems, properly designed and controlled, can lower first costs and operating costs using a variety of strategies including:

• Twin-duct system architecture
• Dual motor fan drives with inlet vanes in lieu of a single motor with inverter
• Heating/cooling changeover of the traditional hot duct
• Direct digital control of terminal units
• Precise control of duct static pressure
• Elimination of return air fan

By utilizing the above concepts and a computerized design program, a system canbedesigned
that retains the low maintenance benefits of traditional dual-duct systems as well as providing the low noise, low cost, energy-efficient systems required to make today’s building profitable.

Units: Dual