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 maintain space temperature by mixing two distinct air streams. A hot deck and a cold deck supply air to a mixing box, where a thermostat-controlled damper proportions the ratio of hot and cold air to achieve the desired discharge temperature, providing precise individual zone climate control.