Number of views: 3623 Author: Aili Industry Release time: 2026-09-29 Source: Ai Li Industrial
The most common problem with a new air conditioning system is not the fan box itself, but the air volume distribution. The design institute gave the total air volume, the HVAC construction pipes were laid out according to the drawings, and the equipment was selected based on the total air volume. During debugging, it was found that the air volume was too high in some areas and not enough in some areas. After checking back, I found that the partition requirements were not balanced, and the usage coefficient was not considered. There is no problem with the device, the problem lies in the system matching.
Direct answer: To match the air volume between the DC fan cabinet and the new air conditioning system, the first step is not to select the equipment, but to balance the air volume among the zones. First, it is clear how much air supply is required for each area, which areas operate at the same time, which branches will be switched on and off at different times, and then summarize the actual total air volume that the air outlet box must bear. This total air volume is not a simple sum of the design air volumes in all areas, but the result of combining the simultaneous use of coefficients and operating modes.
The design air volume of each area comes from the heat and moisture load, fresh air volume, number of personnel and process requirements. Listing these requirements item by item to form a zone air volume balance sheet is the basic work for a new air conditioning system. However, they cannot be added directly when summarizing.
The reason is simple: not all areas reach their maximum load at the same time. Office areas require full air volume during working hours, conference rooms may only be used for meetings, production workshops run on a shift basis, and warehouses may only need to maintain basic ventilation. If the fan cabinet is selected based on the peak operation of all areas at the same time, the equipment will be selected to be too large, and it will operate in the low-load area most of the year, which will waste energy consumption and initial investment.
On the other hand, if you only select based on average load, it may not be enough during peak hours. The correct approach is to analyze the operation schedule of each area, determine the simultaneous use coefficient, and then combine the allowable air volume deviation of the system to obtain the design total air volume. The benefits of the DC fan box are reflected here: it can adjust the speed according to different operating modes, covering peak and valley working conditions, instead of using a fixed speed to carry all periods.
An air conditioning system may have multiple fan boxes, each serving different areas. Before matching the air volume, it is necessary to clarify which branches and terminals each fan box is responsible for.
If two fan cabinets serve adjacent areas, you cannot just look at the sum of their rated air volumes. It is necessary to clarify the ownership and simultaneous operation relationship of each branch. In areas with shared return air or exhaust air, the air volume balance must also be reviewed. For example, one fan box is responsible for the air supply to the east district, and the other is responsible for the west district, but the return air is shared. Changes in air volume in the east zone will affect the return air main pressure, which in turn affects the air supply effect in the west zone. This coupling relationship must be identified during the partitioning stage.
After the branch ownership is clear, let’s talk about the design air volume and speed regulation mode of a single unit. Otherwise, when debugging, it is found that the air volume in a certain area is wrong, and it is not clear which device is the problem.
After the total air volume is determined, the next step is to calculate the resistance of the most unfavorable path. Filter sections, coils, dampers, mufflers, elbows, reductions and straight sections of duct are all accounted for. Add these resistances together to obtain the external static pressure, then combine it with the design air volume to form the working point, and check it on the fan performance curve.
Zone valve switching changes system resistance. After a branch is closed, the resistance curves of other branches will move, and the fan operating point will also change. Therefore, common working conditions should also be listed for checking the DC speed regulation range. The model cannot be selected only according to the working condition when all branches are fully open, nor can it be selected only according to the working condition when some branches are closed.
If the system end configurationFor HEPA/ULPA high-efficiency filters , the initial resistance of the filter and the resistance at the end of use are both included in the working point. When the process requirements are higher, it can be evaluatedDoes the ULPA ultra-high efficiency filter meet the requirements?
System debugging cannot only look at the total air volume at the outlet of the fan box. The total air volume is enough, but it does not mean that each end is enough. If the total air volume is normal but the remote end is insufficient, check the branch balance, air leakage and measuring point location.
Terminal measurement is the only way to verify partition matching. Under design working conditions and common working conditions, measure the air volume of each branch and the air volume or pressure difference at the most unfavorable end. If a certain area is always insufficient, first check the air valve opening, branch balance and air leakage, and then consider adjusting the fan speed. Don't increase the speed as soon as you find that the air volume is insufficient. If the total air volume increases, the problem of uneven distribution may become more serious.
For systems using DC speed regulation, the terminal air volume should also be measured at different speed gears to confirm that the control strategy can cover various typical operating states. When the most unfavorable end still meets the demand at the lowest speed, the lower limit of speed regulation is confirmed.
New projects often have room for adjustment in filter section design. If the system requires filtration, the filtration section can be integrated into the fan box and equipped with primary, medium or high-efficiency filters. But after adding a filter, the working point must be recalculated. The final resistance of the filter may be two to three times the initial resistance, and the length of the box must be increased accordingly.
Aili Industrial has independent supporting capabilities in fans, motors, controls and sheet metal structures. It can consider the installation space of the filter section, air flow channel and inspection opening at the design stage. The matching relationship between the fan and filter is checked from the whole machine level, instead of trying to plug the filter after the box is completed. This kind of internal coordination from the power end to the structural end can reduce the common problems of insufficient filter section resistance estimation and insufficient box space in new projects.
The control mode must also be determined simultaneously. The air volume corresponding to the working mode and the duty mode respectively, what are the switching conditions, where the sensor is installed, and how to act in case of failure should be stated in the control point table. Just writing 'adjustable speed' is not enough. Specific signal types, terminal definitions and action logic are required during on-site debugging.
To accurately match the fan box with the new air conditioning system, the project party should at least provide: partition air volume balance table, operation schedule of each area, simultaneous use coefficient, most unfavorable path pressure loss, filter section configuration and resistance range, power supply conditions, control requirements, installation space and maintenance conditions.
Aili Industrial can discuss based on the zone air volume balance sheet, piping diagram and working hours.DC fan chassis complete machine and control configuration. If the system hasFor high-efficiency air supply outlets (HEPA BOX) , the air volume and quantity of each outlet should also be included in the total of the zones. 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)。
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 shape them based on the determined working points and on-site interfaces.
