What is the role of supply air static pressure control in a BAS?

• A. To measure indoor air temperature.
• B. To log energy usage for the HVAC system.
• C. To maintain desired duct static pressure by modulating dampers or fan speeds, ensuring adequate airflow with energy efficiency.
• D. To predict future occupancy.

Answer: (C)

The main idea is controlling how much pressure the supply air must push through the ductwork to reach all zones. In a BAS, a supply duct pressure sensor feeds a control algorithm that modulates the main fan speed or the position of dampers to hold the duct static pressure at a setpoint. When the system resistance changes—loads change, filters clog, or dampers open/close—the control steps in so airflow to each space stays within the required range. Maintaining the right static pressure avoids wasting energy from an overworked fan and prevents under-delivery of air that could lead to uncomfortable or stale spaces. In short, it keeps adequate, efficient airflow by dynamically balancing pressure in the ducts as conditions vary. This function isn’t about measuring indoor temperature, logging energy usage, or predicting occupancy; those are separate BAS tasks.