The FFU group control percentage setting is the same, why is the wind speed of each unit still different?
The percentage is the same, but the wind speed is not necessarily the same.
In the FFU group control system, operators usually set the same speed adjustment percentage for a group of FFUs, for example, all are set to 70%. After the settings were completed, on-site measurements found that the wind speeds on the outlet surfaces of different FFUs were inconsistent, with some being higher and some being lower.
This situation does not necessarily indicate that there is a problem with the group control system. The speed adjustment percentage is the control setting value, which means the fan receives the same control signal. However, the actual wind speed of FFU also depends on the fan characteristics, filter resistance, air inlet conditions, air path structure and installation status. Under the same settings, the actual operating points of different devices may be different.
Therefore, the same group control percentage is only the unification of the control level and does not represent the unification of the actual air supply. In order for each FFU to reach the target wind speed, it often needs to be calibrated one by one or adjusted by zone. Aili Industrial has complete supporting capabilities in FFU control systems and can provide product solutions from stand-alone controllers to group control systems. For the basic configuration of FFU control and communication, please refer toAili Industrial FFU fan filter unit。
What does the speed adjustment percentage represent?
The speed regulation percentage usually represents the ratio of the speed command output by the controller to the fan relative to the rated speed. 70% means the fan operates at 70% of the rated speed. For DC fans or EC fans, the controller adjusts the speed through PWM or communication instructions. For AC fans with voltage regulation or frequency conversion control, the speed regulation methods are different.
The percentage is the control signal, not the wind speed value. The actual rotation speed of different fans at the same percentage may be different. Even for fans of the same model, the actual speed may vary slightly due to manufacturing differences and different operating conditions.
Therefore, the percentage is suitable as a control setting, but cannot be used directly as a wind speed indicator.
How differences between fans and motors affect wind speed
Different FFU may use different models or different batches of fans and motors. Even if the appearance is the same, the fan performance curves may be different. Motor efficiency, bearing condition and control response also affect actual speed.
If fans from different batches or different suppliers are mixed in the same group of FFU, the actual rotation speed and air volume at the same percentage may be different. For batch projects, it is recommended to record the fan and motor information of each FFU to facilitate subsequent calibration and troubleshooting.
How filter resistance differences affect wind speed
Filter resistance is an important factor affecting the FFU operating point. Within the same set of FFU, filters may come from different batches and have slightly different resistance characteristics. Different installation and sealing conditions of the filter may also affect the actual air volume. The filter has different usage time, different dust accumulation degree, and greater difference in resistance.
At the same rotation speed, the air volume of the FFU with greater resistance is lower, and the air volume of the FFU with smaller resistance is higher. If the group control only sets the percentage and does not adjust according to the filter status, the difference in wind speed will expand as the running time increases.
For projects that require long-term stable air supply, you can consider the constant air volume control method, or regularly adjust the setting value of each FFU based on the actual measured wind speed.
How inlet and air path conditions affect wind speed
The air inlet conditions of the FFU will also affect the actual wind speed. If there are bridges, pipelines or structures above the FFU, the air inlet resistance will increase and the air volume may decrease. If the FFU is located in the corner of the mezzanine or close to the wall, the air intake may be uneven. If multiple FFUs share the same mezzanine, the air inlet distribution may be uneven.
The air path conditions on the outlet side also have an impact. If there is equipment, light fixtures or structures underneath the FFU, airflow may be blocked. If the return air path is not smooth, the FFU operating point will also change.
These conditions may differ in different locations, resulting in differences in wind speeds at the same setting.
How to do unit-by-unit calibration
To reduce wind speed differences, the FFU can be calibrated one by one. The calibration method is to record the corresponding control setting value when each FFU reaches the target wind speed and write it into the group control system. Calibration can be carried out during the installation and commissioning stage, or it can be recalibrated regularly during operation and maintenance.
During calibration, the location of the measuring points, measurement methods and operating status should be recorded. For a zone-controlled system, it can be calibrated by area instead of setting each unit individually. If the project usesFFU/EFU group control touch screen controller orFFU computer group control system can confirm whether the system supports device-by-unit or partition setting and recording.
How to reduce differences in system design
During the system design phase, steps can be taken to reduce wind speed differences. Choose consistent fan and motor configurations to reduce differences in the equipment itself. Filters are managed in batches and try to use filters of the same batch or with similar performance. The air inlet path is designed evenly to avoid partial occlusion. The return air path is smooth, reducing wind path interference. The group control system supports channel-by-channel or partition settings for easy later adjustments.
For areas with high cleanliness requirements, constant air volume control or wind speed feedback control can be considered so that the FFU can still maintain the target air volume when the filter resistance changes.
Issues that should be confirmed in advance during project communication
During the debugging and operation phase of the FFU group control system, it is recommended to confirm the following with the manufacturer: the corresponding relationship between the speed regulation percentage and the rotation speed; whether the fan and motor models are consistent; filter batch and resistance characteristics; air inlet and return air conditions; whether the group control system supports unit-by-station or zone settings; calibration method and recording format; whether constant air volume control is required; the allowable range and processing method of wind speed differences.
If you are debugging the FFU group control system, you can visitAili Industrial FFU fan filter unit to learn about the complete machine configuration, you can also refer toFFU/EFU group control touch screen controller andFFU computer group control system to learn about the control scheme, or contact Aili Industrial for group control debugging support.
in conclusion
The same FFU group control percentage setting does not mean the actual wind speed is the same. The speed adjustment percentage is a control setting, and the actual wind speed is also affected by the fan, filter, air inlet and air path conditions. Reducing wind speed differences requires unit-by-unit calibration or zone adjustment, and reducing differences in equipment and usage conditions during the system design stage.
Aili Industrial has a complete product line in FFU control systems and can provide supporting solutions from stand-alone controllers to group control systems. If you need to know more about FFU group control debugging, you can visitAili Industrial FFU fan filter unit , you are also welcome to contact Aili Industrial for project support.
