Exploring a Multizone To Variable Volume HVAC Controls Retrofit

The U.S. Department of Defense (DOD) has thousands of 10 to 40+ year old multizone air-handling units (AHUs) in operation. These constant volume, variable temperature units are quick to meet space temperature needs, but they can be very energy inefficient. Multizone units deliver a constant volume of air to the building zones serviced, regardless of the actual cooling, heating and ventilation requirements of each zone. Further, the conventional two-deck multizone uses continuous, simultaneous operation of the heating and cooling coils, even when additional heating or cooling is not needed. Modern alternative system replacements (such as variable air volume systems) help address these inefficiencies but are costly and disruptive to install. This article presents an energy savings retrofit of the multizone control system that provides variable volume airflow at significantly lower expense and with less disturbance than a complete system change out.