What air distribution system includes both a warm air duct and a cool air duct and uses mixing boxes near the zone to mix the warm and cool air streams and achieve the desired temperature while delivering air at a near constant volume?

What air distribution system includes both a warm air duct and a cool air duct and uses mixing boxes near the zone to mix the warm and cool air streams and achieve the desired temperature while delivering air at a near constant volume?

• A. Variable air volume (VAV)
• B. Dual duct
• C. Constant-volume single-duct
• D. Multizone terminal units

Answer: (B)

Mixing warm and cool air streams at the zone to reach the desired temperature while keeping the supply air volume essentially constant is the hallmark of a dual-duct system. In this setup there are two separate supply ducts: one carrying heated air and one carrying cooled air. Near each zone, a mixing box blends portions of both streams to achieve the required temperature, and the total air volume delivered to the space remains roughly constant as the temperature is adjusted by changing the mix. This approach is distinct from systems that vary volume, use a single duct, or zone via multizone terminals without mixing separate hot and cold ducts at the zone.

Mixing warm and cool air streams at the zone to reach the desired temperature while keeping the supply air volume essentially constant is the hallmark of a dual-duct system. In this setup there are two separate supply ducts: one carrying heated air and one carrying cooled air. Near each zone, a mixing box blends portions of both streams to achieve the required temperature, and the total air volume delivered to the space remains roughly constant as the temperature is adjusted by changing the mix. This approach is distinct from systems that vary volume, use a single duct, or zone via multizone terminals without mixing separate hot and cold ducts at the zone.