The Dwyer Instruments AAFS Adjustable Air Flow Paddle Switch is a heavy-duty sensing solution engineered to monitor and verify air flow velocity in HVAC and industrial ductwork. Designed to handle air and compatible gases, this unit features a field-adjustable SPDT switch, allowing for precise setpoint selection between 200 to 1800 FPM. As the direct replacement for F40AA-2, it offers a drop-in upgrade for legacy systems requiring reliable proof of flow or low-flow protection. The assembly includes a stainless steel paddle and a rugged flange connection for secure mounting on round or rectangular ducts. The mechanical airflow switch mechanism ensures consistent operation across a temperature range of up to 180°F. For contractors overseeing commercial duct sensor install projects, the AAFS provides a dependable interlock for electric heaters, exhaust fans, and cooling coils, preventing equipment damage during airflow loss or restricted circulation. Key Benefits Field-Adjustable Setpoints: Easily tune the actuation point between 200 and 1800 FPM to match specific system requirements. Rugged Construction: Features a stainless steel paddle and gasketed enclosure for long-term durability in demanding airstreams. Drop-In Compatibility: Serves as a direct functional cross-reference for Johnson Controls F40AA-2, minimizing downtime during retrofits. Versatile Mounting: The included flange bracket simplifies the duct airflow switch wiring and installation process. Reliable Proof of Flow: Provides a discrete dry contact signal to BAS or safety circuits to verify fan operation. Common Questions Can the AAFS be used in a vertical duct?Yes, the unit can be mounted in both horizontal and vertical orientations. However, the setpoint must be adjusted to account for the weight of the paddle when installed in vertical applications. How sensitive is the paddle to turbulent air?To ensure an accurate airflow measurement and prevent switch chatter, the paddle should be installed in a straight duct run at least five diameters downstream and three diameters upstream from elbows or dampers. What is the maximum pressure rating for the housing?The AAFS is designed for standard duct velocities and is typically rated for static pressures up to 10 PSIG. Disclaimer: While we strive for 100% accuracy, product data and specifications are subject to change. Please contact our team to confirm compatibility or technical details before purchasing. AAFS is the cross for AF1-S
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