Number of views: 2663 Author: Aili Industry Release time: 2026-09-29 Source: Ai Li Industrial
On-site feedback that the air volume is too large usually occurs in two situations. One is that the wind feels too strong at the end, making people uncomfortable, or the wind speed in the clean room exceeds the standard. The other is that during debugging, it is found that the total air volume exceeds the design value, but the wind is not felt at the end. The causes of these two situations are different and the treatments are also different.
Excessive air volume is no small matter. Long-term excessive air supply means waste of energy consumption, and may also cause noise, vibration and excessive terminal wind speed. But before dealing with it, you need to figure out where the problem is.
If the air volume at a certain end is too large, it may be due to an imbalance in the balance of the branch. The air volume of the main air duct is normal, but a certain branch valve is opened too wide, and the air flows there, while other branches are not enough. In this case, the branch valve needs to be adjusted to redistribute the air volume instead of reducing the fan speed.
The total air volume of the whole machine is too large, which is another matter. It may be that the fan selection is too large, the system resistance may be lower than the design value, or the speed setting may be too high. If the total air volume is too large but the ratio of each branch is normal, you can consider reducing the speed or adjusting the fan operating point.
The judgment method is very simple: measure the total air volume at the fan outlet and measure the partial air volume at each branch. If the total air volume is normal but the partial air volume is uneven, it is a branch balance problem. If the total air volume itself is large, then look at the rotation speed and system resistance.
During measurement, record the filter status, valve opening and operating gear, and compare them with the debugging baseline under the same conditions. If the last debugging was performed with the filter in a clean state, and now the filter has accumulated dust, the two data cannot be directly compared.
When they find that the air volume is too large, many people's first reaction is to turn down the valve. This method can temporarily solve the problem, but if you rely on valve throttling for a long time, the fan will always run in a high resistance state. The air volume is eaten up by the valve, the energy consumption is not reduced, and the noise may increase.
When the speed regulation capability is available, priority is given to reducing the speed. On the premise of meeting the most unfavorable terminal air volume and pressure difference, reduce the rotation speed to the appropriate position to match the fan output to the system demand. After reducing the speed, the input power of the whole machine will usually decrease, and the noise will also decrease.
But speed reduction cannot only depend on current. Reducing the rotational speed also changes the available pressure. For multi-branch systems, the required air volume or pressure difference should be verified at the most unfavorable end. Merely seeing a drop in current does not prove that the entire system still meets usage requirements. Sensor position and branch balance are equally important. Speed adjustment based only on one measuring point may result in insufficient air volume in the remote area.
If the system does not have speed regulation capability, you can consider installing a frequency converter or switching to a DC speed regulation solution. However, before modification, you must first confirm whether the original motor supports speed regulation, whether the control cabinet has space to install the driver, and whether the power supply capacity is sufficient.
To troubleshoot excessive air volume, it is recommended to proceed in the following order.
The first step is to confirm the measurement method and measuring points. Different instruments, different measuring points, and different measuring sections will have different readings. First use the same method to retest to confirm that the air volume is indeed too high. Check whether the position of the pressure measuring hole is reasonable and whether the air volume measurement section has enough straight pipe sections.
The second step is to compare the air volume of each branch. If the total air volume is too large but the ratio of each branch is normal, the problem lies in the total air volume control. If one branch is obviously too large and other branches are too small, the problem lies in branch balance. If the total air volume is normal but the remote end is insufficient, it means uneven distribution is more prominent than the total volume problem.
The third step is to check the speed and setting value. Check whether the power supply voltage and frequency of the fixed-speed fan case are normal. The speed-regulating fan box checks whether the control signal is consistent with the set value and whether the driver parameters have been modified. Sometimes the air volume is too high just because someone changed the setting value after debugging.
The fourth step is to review whether the system resistance is lower than the design value. During construction, reducing the filter section, shortening the air duct, and changing the valve opening will reduce the system resistance and move the fan working point toward the direction of large air volume. If the actual pipeline deviates significantly from the original design, the fan curve and adjustable range need to be rechecked instead of just changing a set percentage.
The fifth step is to verify the end after adjustment. Regardless of whether speed reduction or valve adjustment is used, the air volume and pressure difference at the critical end must be measured after adjustment to confirm that the farthest end is not affected by reducing the total air volume.
Design changes often occur during construction. The original design had three stages of filtration, but it was changed to two stages during construction; the air duct was originally designed to go to the top, but was later changed to the trench; the original design was to fully open the valve, but later a regulating valve was added. These changes will affect the system resistance and thus the fan operating point.
If the actual pipeline resistance is significantly lower than the design value, the fan will deliver a greater air volume than the design at the original speed. At this time, it is not a device failure, but a change in system conditions. There are two ways to deal with it: one is to reduce the rotational speed and bring the operating point back to the design range; the other is to recalculate and confirm whether the current air volume is within the allowable range. If it exceeds the end bearing capacity, it must be adjusted.
Aili Industrial has independent supporting capabilities in fans, motors, controls and sheet metal structures. It can discuss speed adjustment plans based on the current air volume, external static pressure and input power, and also check whether the motor and driver support the new operating point. The project provides actual pipeline diagrams and measurement data, and the entire machine plan can be rechecked based on the original design instead of simply adjusting a parameter.
The air volume of the fan box is too large, sometimes because the resistance of the terminal equipment changes. System end configurationWhen using a HEPA/ULPA high-efficiency filter , if the filter is replaced in advance or the resistance is lower than expected, the system resistance will decrease and the fan operating point will move in the direction of large air volume. When the process requirements are higher, it can be evaluatedDoes the ULPA ultra-high efficiency filter meet the requirements?
The end of the air duct adoptsWhen using high-efficiency air supply outlets (HEPA BOX) , if the number of terminals or the air volume of a single outlet changes, the total air volume demand of the system will also change. Clean room ceiling air supply is comparableFFU fan filter unit ; centralized management of multiple devices can be matchedThe FFU computer group control system realizes zone speed regulation and status monitoring. Protection of single process equipment can be consideredEquipment-side fan filter unit (EFU) . The division of labor between these equipment and the fan box should be clearly stated on the system flow chart.
Specific structure and configuration options can be found inIt is confirmed in the fan box product catalog that non-standard projects should provide equipment or machine room drawings, and then finalize them based on the determined working points and on-site interfaces.
