Belimo AF24 US - User Manual

The AF Series Spring Return Direct Coupled Actuator is designed for the precise control of air dampers and valves in HVAC systems. These actuators provide a reliable fail-safe operation, ensuring positive close-off on airtight dampers. The spring return system maintains consistent torque to the damper, whether power is applied or not.

Function Description

The AF Series actuators are available in various configurations, including On/Off, proportional, and multi-function (MFT) models, catering to a wide range of control requirements.

On/Off Control: For basic open/close applications, the On/Off models respond to a simple auxiliary contact or manual switch. They are ideal for fail-safe control of dampers, ensuring they return to a pre-defined position (e.g., closed) upon power loss.
Proportional Control: Proportional models modulate dampers in response to a continuous control signal, such as 2 to 10 VDC or 4 to 20 mA. They offer precise positioning for optimal airflow regulation. A 2 to 10 VDC feedback signal is provided for position indication or master-slave applications.
Phasecut Control: The AF24-PC US model operates with a 0 to 20 V phasecut control input, offering another method for proportional modulation in HVAC systems.
Economizer Control: The AF24-ECON-R03 US is specifically designed for stand-alone economizer damper control, utilizing a 3 kΩ mixed air sensor. It features built-in minimum position adjustment and integrated mixed air PI-control, allowing for proportional control of mixed air setpoint.
Multi-Function Technology (MFT): MFT models offer the most versatile control, with configurable parameters for proportional modulation, spring return fail-safe, and various input/output signals. These actuators can be customized for specific applications, including different control ranges, feedback options, and override settings.

Usage Features

The AF Series actuators are designed for ease of installation and flexible application.

Direct Coupling: The actuators mount directly to a damper shaft up to 1.05 inches in diameter using a universal clamp, eliminating the need for complex crankarms and linkages in many applications. This direct coupling reduces labor costs and simplifies setup.
Fail-Safe Operation: A true mechanical spring return ensures that the damper moves to a pre-defined fail-safe position upon power interruption, providing a highly reliable safety mechanism.
Position Indication: A clear, graduated position indicator shows the damper's rotation from 0° to 95°, allowing for easy visual verification of the damper's status.
Adjustable Angle of Rotation: The angle of rotation can be adjusted, with some models offering a range of 35° to 95° using an optional ZDB-AF2 US limiter. This allows for fine-tuning the damper's travel to match specific system requirements.
Manual Override: A manual override crank is supplied with the actuator, enabling manual positioning of the damper for installation, testing, or emergency situations when power is unavailable. This feature speeds up installation and troubleshooting.
Direction of Rotation Switch: Many models include an external switch for reversing the direction of rotation, providing flexibility in mounting and control setup.
Auxiliary Switches: Select models (-S versions) are equipped with two built-in SPDT auxiliary switches. These switches can be used for safety interfacing, signaling, or fan start-up. One switch is fixed at +5° from the fail-safe position, while the other is adjustable between +25° and +85°.
Overload Protection: The actuators are protected from overload throughout their entire rotation range, preventing damage even if the damper stalls.
Environmental Robustness: The rugged metal housing withstands rough handling in mechanical rooms. The Golden Point breather membrane optimizes performance in harsh airstream environments by eliminating internal condensation.
Cable Options: Available with plenum-rated or appliance-rated cables (18 GA), and a 1/2" conduit connector for easy electrical connection.
Double Insulation: Many 120V and 230V models feature double insulation, eliminating the need for a separate safety ground connection.
Damper Seal Wear Compensation: The actuators automatically compensate for damper seal wear, ensuring a tight close-off over time.

Maintenance Features

The AF Series actuators are designed for minimal maintenance and long service life.

Brushless DC Motor: Utilizing microprocessor-controlled brushless DC motors, these actuators offer increased life span and reliability compared to conventional DC motors. The brushless design eliminates wear components like brushes and commutators.
Maintenance-Free Design: The actuators are designed to be maintenance-free, reducing operational costs and downtime.
Digital Rotation Sensing (DRS): The ASIC (Application Specific Integrated Circuit) and microprocessor monitor and control the motor's rotation, providing a digital rotation sensing function that prevents damage in stall conditions. This eliminates the need for mechanical end switches.
Constant Running Time: The microprocessor ensures a constant running time, independent of the load, for consistent performance.
Control Accuracy and Stability: AF24-SR US actuators feature a non-symmetrical deadband and high resolution (80 mV) for precise control. They are designed to ignore minor input signal fluctuations while responding accurately to significant changes, enhancing system stability.
Initialization Memory: For proportional models, the actuator memorizes its zero position upon initial power application and retains this information during short power failures (up to 20 seconds). This ensures consistent control even after brief interruptions.