Referring to the illustrated dual duct multiple zone HVAC system, how is the space temperature directly controlled? GS-RA-43 Illustration GS-RA-43: the U.S. Coast Guard has not released this illustration.

Correct Answer: Option A — The space air temperature is controlled by automatically proportioning the cold and hot air streams at the mixing unit.

Dual duct systems control space temperature by modulating the mixing dampers at the terminal unit. By varying the ratio of cold air from the cold duct and warm air from the hot duct, the system achieves the specific temperature setpoint required for the zone without altering the total air volume.