The Belimo AFB24-SR is a fail-safe damper actuator designed for use in heating, ventilation, and air conditioning (HVAC) systems. As a spring-return (fail-safe) actuator, it ensures reliable positioning of dampers in the event of a power failure. With a torque rating of 180 in-lb and support for both 24VAC and 24VDC power inputs, the AFB24-SR is suited for applications requiring modulating control via a 2-10VDC signal. This article provides a detailed overview of its key technical specifications, installation considerations, and wiring guidance, based on the information provided in the source materials.
The Belimo AFB24-SR is manufactured with a degree of protection rated as IP42, which means it is protected against solid objects larger than 1 mm and splashing water. It also meets the NEMA 2 standard, indicating it is suitable for indoor use in non-hazardous locations. The actuator is equipped with a manual override feature, allowing users to adjust the damper manually using a 5 mm hex crank. The actuator’s enclosure is not rated for NEMA 4X, meaning it is not suitable for environments requiring protection against corrosion or high levels of water exposure.
The actuator is designed to operate in ambient temperatures ranging from -22°F to 122°F (-30°C to 50°C), making it suitable for a wide range of climate conditions. Its power consumption is relatively low, with a running power draw of 5.5 W and a holding power draw of 3 W. The motor operates for approximately 95 seconds per 90-degree rotation, and the fail-safe function engages within less than 20 seconds when power is lost.
The following sections explore the installation process, wiring requirements, and key technical features of the Belimo AFB24-SR actuator, based on the information provided in the source materials.
Installation Process for the Belimo AFB24-SR
The installation of the Belimo AFB24-SR involves several key steps to ensure proper functionality and safety. While the provided source material does not include a detailed, step-by-step installation manual, it references installation instructions as part of the product documentation. Users are advised to consult the official Belimo AFB Series Installation Instructions for a comprehensive guide.
The actuator includes a manual override feature that allows for manual adjustment of the damper using a 5 mm hex crank. This feature is particularly useful during installation for initial positioning or in the event of a power outage. The actuator’s direction of rotation is reversible with cw (clockwise) or ccw (counterclockwise) mounting, which should be configured according to the damper’s mechanical setup.
The actuator is designed with a switch that allows users to select the direction of motion for the motor. This switch is typically set to 0 or 1 and should be adjusted based on the damper’s orientation. Proper configuration of this switch is essential to ensure the actuator moves the damper in the correct direction.
When installing the actuator, it is important to ensure that the mechanical linkage between the actuator and the damper is properly aligned. The actuator must be mounted securely to prevent vibration or misalignment, which could affect its performance or lead to mechanical failure. The actuator’s mounting method should be selected based on the damper’s design and the available mounting points.
The angle of rotation for the AFB24-SR is 95 degrees. This means the actuator can move the damper through a full 95-degree arc, which is suitable for a wide range of damper sizes and configurations. The user should verify that the damper can accommodate this range of motion without exceeding its mechanical limits.
The actuator is not rated for NEMA 4X protection, so it should only be installed in indoor environments where it is not exposed to moisture, corrosion, or high levels of dust. It is also important to ensure that the ambient temperature remains within the specified range of -22°F to 122°F (-30°C to 50°C) to prevent overheating or freezing.
Wiring Requirements and Control Signals
The Belimo AFB24-SR is controlled using a 2-10VDC signal, which allows for modulating control of the damper position. This signal is typically provided by a building automation system or a thermostat, which adjusts the voltage to control the actuator’s position. The actuator interprets the voltage level and adjusts the damper accordingly.
The actuator supports both 24VAC and 24VDC power inputs. This dual-voltage capability makes it compatible with a wide range of power supplies and control systems. The power consumption during operation is 5.5 W, and during holding (when the damper is stationary), it is 3 W. The total power consumption for wire sizing is 8.5 VA, which should be considered when selecting the appropriate wiring and circuit protection.
The source material references a wiring guide for the AFB24-SR, which is typically used for most Belimo fail-safe modulating actuators. However, it is important to note that the AFB24-MFT95 model is an exception and should not use the same wiring diagram. Users are advised to verify that the wiring diagram they are using is appropriate for the AFB24-SR model.
The wiring process involves connecting the actuator to the control system, power supply, and damper mechanism. The control signal wires should be connected to the appropriate terminals on the actuator, ensuring that the polarity is correct. The power supply wires should also be connected to the designated terminals, and the actuator should be grounded according to electrical codes and standards.
The actuator does not include an auxiliary switch, meaning it does not provide direct feedback on the damper’s position or status. Instead, position feedback must be obtained from the control system or through an external sensor. This limitation should be considered when designing the control system and selecting the appropriate components.
Fail-Safe Functionality and Emergency Operation
One of the key features of the Belimo AFB24-SR is its fail-safe functionality. In the event of a power failure, the actuator engages a spring-return mechanism that moves the damper to a predefined position. This ensures that the damper remains in a safe position, which can help prevent damage to the system or maintain environmental conditions during an outage.
The fail-safe function engages within less than 20 seconds after power is lost, which is significantly faster than the actuator’s normal running time of 95 seconds per 90-degree rotation. This rapid response time is essential for applications where immediate positioning is required to maintain safety or comfort.
The direction of the fail-safe movement is determined by the actuator’s mounting orientation. The actuator can be mounted in either a clockwise (cw) or counterclockwise (ccw) direction, which affects the direction of the damper’s movement when the fail-safe function is activated. Users should ensure that the mounting orientation is selected based on the damper’s mechanical design and the desired fail-safe position.
The manual override feature is another important aspect of the actuator’s emergency operation. In the event of a power failure or control system malfunction, the damper can be manually adjusted using a 5 mm hex crank. This allows for temporary adjustments or full control of the damper without relying on electrical power. The manual override should be used with care to avoid damaging the actuator or the damper mechanism.
When using the manual override, users should ensure that the actuator is in the correct position before initiating manual movement. It is also important to return the actuator to the automatic mode after manual adjustments are made. Failure to do so could result in conflicts between the manual and automatic controls, which could lead to system instability or mechanical damage.
Compatibility and System Integration
The Belimo AFB24-SR is compatible with a wide range of HVAC systems and control architectures. It is designed to work with 24VAC and 24VDC power supplies, which are commonly used in commercial and residential HVAC applications. The actuator’s modulating control signal (2-10VDC) allows it to be integrated with programmable thermostats, building management systems, and other automation platforms.
The actuator’s low power consumption and compact design make it suitable for use in both new installations and retrofit projects. It can be used with a variety of damper types, including round, rectangular, and blade-style dampers, as long as the mechanical linkage is properly configured. The actuator’s mounting methods are flexible, allowing it to be adapted to different damper designs and installation requirements.
The actuator is not rated for NEMA 4X protection, so it is not suitable for outdoor installations or environments with high levels of moisture, dust, or corrosive elements. It should only be used in indoor HVAC applications where it is protected from environmental hazards. The actuator’s operating temperature range of -22°F to 122°F (-30°C to 50°C) makes it suitable for most climate-controlled environments, but it should not be used in areas with extreme temperatures or humidity.
The actuator’s IP42 rating provides protection against solid objects larger than 1 mm and splashing water, which is sufficient for most indoor HVAC applications. However, it does not provide protection against water immersion or high-pressure water jets. Users should ensure that the actuator is installed in a location where it is not exposed to direct water contact or high humidity levels.
The actuator’s compatibility with both AC and DC power sources makes it a versatile option for a wide range of control systems. It can be used with traditional low-voltage HVAC systems or integrated with modern smart HVAC systems that use digital control signals. The actuator’s modulating control signal allows for precise damper positioning, which can help improve energy efficiency and comfort levels in buildings.
Conclusion
The Belimo AFB24-SR is a versatile and reliable damper actuator designed for use in a wide range of HVAC applications. Its fail-safe functionality ensures that the damper remains in a safe position during power outages, while its modulating control signal allows for precise damper positioning. The actuator’s low power consumption, compact design, and compatibility with both AC and DC power sources make it a suitable option for both new and retrofit HVAC systems.
The actuator is equipped with a manual override feature that allows for manual adjustment of the damper, which is useful during installation or in the event of a power failure. The actuator’s direction of rotation can be adjusted based on the damper’s orientation, and the motor’s running time is optimized for efficient operation.
Users should ensure that the actuator is installed in a location that meets its environmental requirements, including the specified temperature range and protection from moisture and dust. The actuator’s wiring should be configured according to the provided wiring diagram, and users should verify that the control signal is properly connected to the actuator’s input terminals.
The actuator is not rated for NEMA 4X protection, so it should only be used in indoor environments where it is not exposed to high levels of moisture or corrosion. The actuator’s IP42 rating provides sufficient protection for most indoor HVAC applications, but users should ensure that it is installed in a dry and dust-free location.
Overall, the Belimo AFB24-SR is a reliable and efficient actuator that offers a balance of performance, durability, and ease of use. Its fail-safe functionality, modulating control, and low power consumption make it a valuable component in modern HVAC systems, particularly in applications where precise damper control and system safety are critical.