1. How to Determine Damper Size Based on Airflow?
The relationship between airflow and effective free area is:
Q = 3600 × A × V
Where:
Q: Airflow, m³/h;
A: Effective free area, m²;
V: Air velocity through the damper, m/s.
For example, if the design airflow is 3,600 m³/h and the selected air velocity is 5 m/s, the theoretical free area is approximately 0.20 m². However, the area occupied by the blades, shafts, and frame must also be considered. Therefore, the duct cross-sectional area cannot be used directly as the effective free area.
If the damper is too small, air velocity, noise, and pressure loss will increase. If it is too large, the damper may operate within a small opening range for long periods, reducing control stability. The final size should be confirmed according to the manufacturer’s selection data.
2. How to Match the Damper with the Duct Size?
An AV Damper is generally selected according to the width and height of the connecting duct, such as 500 × 400 mm. For circular ducts, the diameter and flange type must be confirmed.
The following items should be checked during selection:
Whether the dimensions refer to the duct’s internal size or the flange’s external size;
Whether the connection is rectangular, circular, or specially shaped;
Flange width and bolt-hole requirements;
Horizontal or vertical installation direction;
Whether sufficient maintenance space is available on the actuator side.
Large rectangular dampers may require multiple blades, segmented frames, or multiple actuators. Simply enlarging a single damper body may result in blade deformation, poor shutoff performance, or insufficient actuator torque.
3. How to Select the Control Signal?
The control signal must be compatible with the building control system, thermostat, or DDC controller.
| Control Method | Typical Application |
|---|---|
| Manual | Manual commissioning and airflow balancing |
| On/Off | Fully open and fully closed control |
| 3-Point/Floating | Open, stop, and close control |
| 0–10V or 2–10V | Continuous proportional control |
| 4–20mA | Industrial control systems |
| Modbus/BACnet | BMS digital communication |
If the system needs to continuously adjust airflow according to temperature, pressure, or CO₂ concentration, a modulating actuator should be selected. If only start/stop or interlock control is required, an on/off actuator can be used.
The power supply, such as AC/DC 24V or AC 220V, must also be confirmed during procurement. Buyers should also specify whether position feedback, spring return, and power-failure protection functions are required.
4. How to Determine Actuator Torque?
Actuator torque is related to the damper size, number of blades, sealing-strip friction, system static pressure, and operating time. High-pressure systems, dampers with sealing structures, and large dampers generally require higher torque.
Insufficient actuator torque may cause:
The blades to fail to open or close completely;
The actual opening position to differ from the control signal;
Long-term motor overload;
Increased closed-damper leakage.
It is recommended that the damper manufacturer calculate the required torque according to the damper structure and retain a reasonable safety margin. Selection should not be based solely on actuator price.
5. How Should Different Projects Be Configured?
General Supply and Return Air Systems
Manual or modulating AV Dampers can be selected for system balancing and zoned airflow adjustment.
Variable Air Volume Air-Conditioning Systems
A modulating actuator should be installed and linked with temperature, static-pressure, or airflow sensors. If the project requires accurate maintenance of the set airflow, an airflow measurement device and controller should also be installed. A standard damper alone cannot directly guarantee constant airflow.
Cleanrooms and Laboratories
In addition to airflow, shutoff leakage, materials, corrosion resistance, response speed, and BMS communication must be confirmed. When room pressure differential control is involved, the supply-air and exhaust-air dampers should be integrated into a unified control sequence.
Industrial Exhaust Systems
Galvanized steel, stainless steel, aluminum alloy, or corrosion-resistant coated structures should be selected according to dust, corrosive gases, temperature, and humidity.
6. Common Procurement Questions
Must the Damper Size Be Exactly the Same as the Duct Size?
It should generally match the duct connection. If a transition is required, airflow distribution, local pressure loss, and installation space should be evaluated to avoid sudden changes in duct size immediately before or after the damper.
Can a 0–10V Actuator Be Connected to an On/Off Signal?
It cannot be used as a direct replacement. The actuator input signal, supply voltage, and controller output must be compatible.
Can an AV Damper Replace a VAV Box?
A standard AV Damper mainly adjusts the opening position. A VAV Box generally includes an airflow measurement device, controller, and actuator. If closed-loop constant-airflow or variable-airflow control is required, a complete set of control components must be installed.
7. Yueboyang AV Damper Solutions
Jiangsu Yueboyang Purification Equipment can provide rectangular or circular AV Damper selection according to the design airflow, duct dimensions, system static pressure, and control method. Customization is available for the damper body material, actuator, control signal, and connection dimensions.
When requesting a quotation, it is recommended to submit the Airflow Schedule, Duct Size, and Control Sequence together. This allows the damper specifications, actuator torque, and control interface to be determined accurately, reducing the risk of reselection and recommissioning after installation.
