Why is the actual air volume of the EFU lower than the rated value? System resistance and operating point analysis

Straight answer: The actual air volume of the EFU is lower than the sample rating, which usually does not equal a fan failure. The fan operating point is determined by the intersection of the fan performance curve and the system resistance curve. After being installed on the equipment, the air inlet grille, filter, box, air outlet structure and internal path of the equipment will jointly increase the resistance and the working point will change.

First confirm the test conditions for the rated value

Check whether the rated air volume is obtained under free air supply, specified filter initial resistance or a certain static pressure, and confirm the voltage, frequency and speed gears at the same time. If the working conditions are different, the values ​​cannot be directly compared.

Check whether the air inlet side is blocked

Insufficient distance between the upper cover, small return air outlet area, wire harness blocking the fan entrance, or dust accumulation on the air inlet net will increase the entrance loss. Inlet bias flow may also be accompanied by noise changes.

Check filter and seal status

If the filter is dusty, damp, or has a higher resistance specification, the pressure difference will increase. Poor sealing sometimes causes partial bypass and abnormal wind speed distribution measured on the surface. You cannot just look at the total air volume.

Check the structure of the equipment on the air outlet side

Additional back pressure may be created by dense structures, orifice plates, fairings or narrow channels beneath the filter. For device-side EFU, it should be evaluated in a state close to the actual installation.

Eliminate control and measurement deviations

Confirm controller settings, communication instructions, work and duty modes, power supply voltage and speed feedback. Wind speed measurement should unify measuring points, distances, grids and instruments to avoid a single point value representing the entire wind outlet surface.

Adjust in sequence instead of directly increasing the speed

It is recommended to check the working conditions, clean the air inlet, measure the filter pressure difference, check the structural resistance, and then adjust the speed. After increasing the speed, the power, noise, temperature rise and uniformity must be re-measured.

FAQ

Is it possible that the air volume is insufficient even after installing the new filter?

possible. The filter specifications or resistance are different from the original design, or the installation seal and orientation are incorrect.

Can the total air volume be determined by measuring an anemometer?

cannot. Multiple points should be measured on a grid and converted by effective area.

What should I do if the speed reaches 100% but is still insufficient?

System resistance and fan selection should be rechecked to avoid exceeding the reasonable operating range for a long time.

How does Aili Industry cooperate with equipment-side EFU projects?

Aili Industry carries out R&D and production around EFU complete machines, fans and motors, control systems, sheet metal structures and air filters. For equipment-side projects, configuration can be carried out based on equipment drawings, target air volume, static pressure, filtration efficiency, installation interface and control logic. When it comes to ultra-thin, small size or special interfaces, it is recommended to confirm the drawings and agreed working conditions first, and then test the curing parameters through the prototype so that the configuration can be consistent in subsequent mass production.

During project consultation, the available internal length, width and height of the equipment, target cleanliness, air supply area, air volume or wind speed requirements, filtration efficiency, power supply and communication methods can be provided to facilitate quick judgment of whether standard products are suitable or whether non-standard design is required.

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Conclusion: The rated air volume of EFU must correspond to specific test conditions. After installation, increased system resistance, inlet bias, filter pressure difference, equipment blocking, or changes in speed setting will all shift the actual working point and reduce the air volume.