How do I size an actuator for a large outdoor air damper?

For large outdoor air dampers (>2 m² face area), actuator sizing must account for wind loading (wind gusts to 30 mph can add 0.2–0.5 in. w.g. pressure differential) and seal breakaway torque, which can be 30–50% higher than running torque on dampers with blade edge seals that have taken a set. Belimo recommends 20 N·m actuators for dampers between 2–4 m² and jackshafting with dual actuators for dampers exceeding 4 m². Spring-return actuators are required per NFPA 90A for smoke control, with NEMA 4/IP66 enclosures for weather exposure.