Likewise, the large central fans in the HVAC system must speed up and slow down to maintain adequate airflow volumes and pressure throughout the system. Those changes, in turn, further impact the static pressure throughout the duct system, so the set of VAV boxes end up in a frequent state of re-adjustment. The other VAV boxes in the network must then adjust their settings to maintain the airflows their spaces require. Namely, as one VAV box receives a signal from the space it controls to increase or decrease the airflow into that space, the change in that valve’s position impacts the static pressure in the duct system. As the network of ducts leading from the central heating and cooling system typically includes multiple VAV boxes, this tends to create an inherent inefficiency in the HVAC system. VAV boxes receive signals to adjust their dampers from controls placed in the space, or from the building automation system (BAS). That’s why venturi valves are increasingly being used for labs and other critical environments. But, in a lab or other crucial environment, lack of precise airflow control can cause injury or death. ![]() In an office building, for example, precise airflow control is not a matter of life or death, as occupants usually don’t notice the airflow variance. ![]() VAV boxes function fine in thousands of buildings around the world. The boxes are calibrated dampers that use a butterfly/blade device to regulate airflow into a space. VAV boxes control the volume of heated or cooled air entering a space in order to manage temperature, humidity, and ventilation.
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