In a modern building automation system, which statement best describes the role of a field controller?

• A. Schedules maintenance tasks only
• B. Monitors energy prices and optimizes billing
• C. Replaces the BAS in the building
• D. Runs local control logic, interfaces with local sensors/actuators, and communicates with the BAS

Answer: (D)

Field controllers act as the local brain near the equipment, running the control logic that directly interfaces with sensors and actuators. They continuously read local measurements (like temperature or flow), make real-time decisions, and drive devices (valves, dampers, fans) to maintain the desired conditions. At the same time, they communicate with the building automation system to report status, receive setpoints, alarms, and instructions, enabling coordinated, centralized oversight while keeping fast, local control in place. The other ideas miss the core function: maintenance scheduling is handled by separate systems, monitoring energy prices and billing is an EMS/billing function, and the BAS is not replaced by a field controller—the field controller is a component that supports the BAS with local control and device interfacing.