Dual Duct System or Double Duct System Dual Duct System or Double Duct System Dual or double duct system is an air conditioning system in which dehumidified air is circulated throughout a building via two parallel ducts.
Hot air flows within one duct, cold air within the other.
A central plant supplies both cold and hot air. The proportion of hot and cold air delivered to each room within the building may be controlled by thermostatically operated dampers on the ducts outlet.