Which of the following events will not require a shutdown of the supply air fan?

• A. Open isolation dampers
• B. Close isolation dampers
• C. Shut off outside air
• D. Turn off the main power

Answer: (A)

Opening isolation dampers reopens the airflow path, so air can continue to be supplied to the spaces without stopping the fan. The fan keeps running because there is still demand for conditioned air; no interlock or power cut is triggered by simply removing the barrier that was isolating a zone.

Closing isolation dampers, shutting off outside air, or turning off the main power all remove or severely reduce the system’s demand, or cut power to the equipment, which typically triggers a shutdown sequence for the supply air fan.