What defines a closed-loop control system in BAS?

What defines a closed-loop control system in BAS?

• A. It uses feedback from the process variable to adjust a manipulated variable to reduce error.
• B. It operates with no sensors.
• C. It uses only manual commands.
• D. It always runs at full capacity.

Answer: (A)

Closed-loop control in BAS relies on feedback to keep a process at its desired value. The system senses the actual process variable with a sensor, compares it to the setpoint, and the controller computes the difference (the error). It then adjusts a manipulated variable—like valve position, damper, or fan speed—to drive that error toward zero. This ongoing loop lets the system respond to disturbances and keep conditions (such as temperature or humidity) near the target. So, using feedback from the sensor to continuously adjust the actuator to reduce error is what makes a BAS system closed-loop. In contrast, running without sensors, relying only on manual commands, or operating at a constant full capacity lacks that automatic feedback mechanism, which is why those descriptions refer to open-loop or non-feedback operation.

Closed-loop control in BAS relies on feedback to keep a process at its desired value. The system senses the actual process variable with a sensor, compares it to the setpoint, and the controller computes the difference (the error). It then adjusts a manipulated variable—like valve position, damper, or fan speed—to drive that error toward zero. This ongoing loop lets the system respond to disturbances and keep conditions (such as temperature or humidity) near the target.

So, using feedback from the sensor to continuously adjust the actuator to reduce error is what makes a BAS system closed-loop. In contrast, running without sensors, relying only on manual commands, or operating at a constant full capacity lacks that automatic feedback mechanism, which is why those descriptions refer to open-loop or non-feedback operation.