How to judge the abnormal working point of EFU fan? Operating data, failure causes and inspection sequence

The working point of the EFU fan is abnormal, and a 'working point offset' fault code is often not directly reported when the equipment is running. It manifests as the air volume failing to reach the set value, the wind speed distribution becoming worse, or the current of the fan at a certain speed being high and the noise becoming louder. What the operator may see is 'cleanliness fluctuations' or 'low wind speed', but the root cause at the working point has deviated from the designed position. The working point is the intersection of the fan performance curve and the system resistance curve. To determine whether it is abnormal, you need to look at the rotation speed, current, static pressure and filter pressure difference together, rather than just focusing on the air volume. Aili Industrial's 70mm ultra-thin EFU uses a self-developed EC brushless motor and dynamically balanced impeller. The fan operating point parameters are marked in the confirmation diagram to facilitate comparison by equipment manufacturers during the prototype and operation and maintenance phases.

Operating data: Putting the four parameters together has diagnostic value

To determine whether the working point of the EFU fan is abnormal, the air volume alone is insufficient. The decrease in air volume may be caused by clogged filters, blocked air ducts, insufficient rotational speed or reduced motor performance. The corresponding treatment methods for these reasons are completely different. There are at least four parameters that need to be recorded simultaneously: set speed or control command value, 、actual speed feedback, 、operating current or 、pressure difference before and after the power filter.。

If the actual speed is lower than the set value, the problem may be with the controller or motor drive; if the speed is normal but the air volume is low, and the filter pressure difference increases, the filter resistance increases; if the speed and pressure difference are normal but the current is high, you need to check whether there are foreign objects in the fan impeller, whether the bearings are worn, or whether there is additional obstruction in the air duct. Aili Industrial EFU control solution supports RS485/Modbus to read operating parameters. Equipment manufacturers can connect speed, current and pressure difference data to the equipment maintenance system to trigger inspections when the working point deviates from the baseline.

For the reading of fan performance curve and operating point, please refer toHow to view the EFU fan performance curve? air volume, static pressure, power and operating point . Description of The essence of the working point abnormality is that the deviation between the actual operating position of the fan and the design intersection exceeds the allowable range, rather than that a certain parameter 'looks wrong' alone.

Cause of failure: first divide the system side, then divide the fan side

The reason for the shift of the working point can be investigated separately according to the two lines of 'change in system resistance' and 'change in fan itself'. First confirm the system side, and then suspect the fan side. If the order is reversed, it will be easy to dismantle the fan in vain.

System-side causes are more common. Dust accumulation on the filter is the primary factor: HEPA/ULPA filter resistance increases with operating time, and the fan's working point will move along the performance curve toward small air volume and high static pressure at constant speed. Blockage of the air duct (the air inlet is blocked, the return air path is changed by the internal structure of the equipment) will also produce similar effects. The equipment-side EFU also faces a special factor: the internal back pressure of the equipment may fluctuate due to process changes, the position of the robotic arm, or the opening and closing of the chamber door. The working point changes dynamically, rather than being fixed at one point. Aili Industrial's EFU application guide also lists 'filter clogging, fan problems or air flow obstruction' as the main investigation directions for insufficient air volume.

Reasons on the fan side include: dust or foreign matter on the impeller causing changes in dynamic balance and reduced efficiency, bearing wear and increased mechanical resistance, performance degradation of the motor winding or drive circuit, and inconsistent speed control signals and feedback. The ultra-thin EFU box has a compact space, and the gap between the impeller and the box wall is small. The entry of foreign matter will have a more obvious impact on the working point than the standard model. Regarding the constraints on matching the air duct and impeller of ultra-thin models, please refer toHow to choose ultra-thin EFU fan? Space, Air Volume Static Pressure, Heat Dissipation and Maintenance Points .Instructions in

Inspection order: from outside to inside, from parameters to components

To check for abnormal working points, it is recommended to proceed in the order of ' data comparison → system side → fan side '. Each step must have a clear basis for judgment before proceeding to the next step.

The first step is to retrieve the benchmark and compare it with the actual measured data . The speed-air volume-current-pressure difference reference values ​​recorded when a new machine is put into operation or the first one is verified are the only basis for judging abnormalities. Without benchmark data, we can only use the rated values ​​in the sample book as a reference, and the sample values ​​are often different from the actual operating points in the equipment. Compare the direction and amplitude of the deviation of the measured value from the benchmark, and initially determine whether it is a gradual deviation (dust accumulation on the filter, bearing wear) or a step deviation (the entry of foreign matter, loose wiring, abnormal control signals).

The second step is to confirm the system side conditions . Read the filter pressure difference and compare it with the replacement threshold; check whether there are new obstructions or structural changes in the air inlet and return air path; confirm whether the back pressure condition inside the equipment is consistent with the baseline record. If the pressure difference is close to the threshold, replace the filter and re-measure the operating point to see if it recovers. This step does not require disassembly of the EFU, is the lowest cost, and should be completed first.

The third step is to check the fan side . After the system side confirms that it is normal, then check the EFU body. Manually turn the impeller to feel whether the resistance is uniform, and observe whether there is dust or foreign matter on the impeller surface; use infrared temperature measurement to compare the motor housing temperature with the historical value; check whether the controller speed feedback is consistent with the setting. If the above are normal but the working point is still deviated, it may be necessary to remove the EFU and retest it on the bench to isolate the influence of the equipment back pressure and determine whether it is a problem with the EFU itself or changes in equipment installation conditions. For troubleshooting the correlation between power abnormalities and motor status, please refer toWhat is the reason for EFU power abnormality? inspection sequence, processing methods and preventive measures .Inspection logic in

Misunderstandings to avoid

It should be avoided to judge the operating point abnormality by only measuring the air volume without looking at the rotation speed and pressure difference. It should be avoided to use the sample book rating as the qualification line without reference data. It should be avoided to disassemble the fan first and then check the filter. It should be avoided to continue to use the original working point reference after the equipment back pressure condition changes. The core of the EFU fan operating point judgment is not 'a certain parameter is high or low', but the speed, current, static pressure and pressure difference form a traceable comparison chain. Changes on the system side are first eliminated, and then the status of the fan side is confirmed.

Related questions and answers

The EFU air volume is 15% lower than the designed value. How to determine whether the problem is the filter or the fan?
Read the filter differential pressure first. If the pressure difference is close to the replacement threshold, the decrease in air volume is most likely due to an increase in filter resistance. This can be confirmed by retesting after replacement. If the pressure difference is normal but the air volume is low, check whether the actual speed reaches the set value and whether the air inlet is blocked. Only when the rotation speed and pressure difference are normal will the fan side issues be considered.

Are operating point abnormality and power abnormality the same thing?
There is overlap but not exactly the same. The power anomaly focuses on the deviation of the motor input power from the baseline, and the operating point anomaly focuses on the deviation of the fan's operating position on the performance curve. The clogging of the filter will cause the working point to shift, and the power may increase (speed compensation under constant air volume control) or remain unchanged (air volume decreases under constant speed control). The two need to be judged together with the rotation speed and pressure difference.

Will changes in back pressure inside the equipment affect the operating point?
meeting. The air outlet side of the equipment-side EFU faces the robotic arm, stage or cavity structure, and the back pressure is not a fixed value. During the process, if the air outlet path is blocked or the chamber door is opened or closed, the working point will move on the performance curve. To determine whether the working point is 'abnormal', it is necessary to distinguish between normal process fluctuations and persistent deviations. The former is within design expectations, while the latter needs to be investigated.

Related articles

How to view the EFU fan performance curve? Air volume, static pressure, power and working point

How to choose ultra-thin EFU fan? Space, air volume, static pressure, heat dissipation and maintenance points

What is the reason for EFU power abnormality? Inspection sequence, processing methods and preventive measures

Key points for selection and acceptance inspection

Aili Industrial EFU selection and procurement support

Aili Industrial's 70mm ultra-thin EFU uses a self-developed EC brushless DC motor and a dynamically balanced aluminum alloy impeller. The fan operating point parameters are marked in the confirmation diagram. The control scheme supports RS485/Modbus to read operating data such as speed and current. The equipment factory can record the working point benchmark during the first unit verification. During the operation and maintenance phase, the deviation direction can be determined by comparison with the benchmark, and then the system side → fan side can be checked in order.

Learn about Aili Industrial EFU products and customized configurations. Check out the compact models.70mm ultra-thin EFU , the entire machine structure can be viewedEFU equipment fan filter unit , the control scheme can be viewedDC speed regulating EFU equipment fan filter unit . Please submit equipment operating conditions, EFU models and descriptions of abnormal phenomena at working points to facilitate confirmation of baseline parameters and troubleshooting suggestions.