What is the difference between FFU external static pressure and fan full pressure? How to unify parameter comparison
Why are the two pressure parameters often lumped together?
In FFU selection and parameter comparison, external static pressure and fan total pressure are two concepts that are often used interchangeably. Some suppliers mark the fan's full pressure on their samples, and some mark the external static pressure of the machine. If the purchaser directly compares the two figures, it is easy to draw wrong conclusions.
Both parameters themselves describe pressure, but their measurement boundaries differ. The total pressure of the fan describes the pressure difference between the inlet and outlet of the fan, and the external static pressure describes the static pressure capacity that the whole machine can provide to the external system at a specified air volume. One is for the fan body, and the other is for the external output of the whole machine. Before comparing them together, you must first confirm whether the test conditions are consistent.
During the FFU complete machine testing and parameter compilation, Aili Industrial usually explains the measurement boundaries and test conditions together to avoid caliber misalignment when customers compare data from different manufacturers. For the basic structure of the FFU machine, you can refer toAili Industrial FFU fan filter unit。
What does fan full pressure describe?
The total pressure of the fan is the difference between the total pressure at the outlet of the fan and the total pressure at the inlet, including dynamic pressure and static pressure. It reflects the total energy increment that the fan itself can provide at a specific speed and air volume. Fan full pressure is usually used for fan selection and fan performance curve expression. The test object is the fan body, excluding FFU box, filter and other additional structures.
It should be noted that the full pressure of the fan is not equal to the external pressure of the FFU complete machine. Because when the air flows inside the FFU, it will pass through the box, filter, sealing structure, air outlet surface and other components, which will cause resistance loss. Part of the total pressure provided by the fan is consumed inside the whole machine, and the part that can really be used to overcome the resistance of the external system is the external static pressure.
What does external static pressure describe?
The static pressure outside the machine is the static pressure capacity that the outlet side of the FFU machine can provide relative to the air inlet side under a specified air volume. It reflects the pressure margin available to the external system of the whole machine, and is usually used to determine whether the FFU can overcome external resistance such as air supply ducts, high-efficiency air supply outlets, and room return air paths.
The test object of the external static pressure of the machine is the whole machine, which usually includes the FFU box, fan, filter and the internal structure in standard configuration. When different manufacturers test the external static pressure of the machine, whether they include a filter, what filter they use, and the test air volume will all affect the results. Therefore, when comparing external static pressure data, the test conditions must be confirmed at the same time.
Common misunderstandings when comparing two parameters
The first misunderstanding is to use the full pressure of the bare fan directly as the static pressure of the whole machine. The full pressure of the fan is obtained under the test conditions of the fan body. There are filters and box resistances inside the FFU machine. The actual static pressure available for external use will be lower than the full pressure of the fan.
The second misconception is to ignore the impact of filters. Whether the FFU is equipped with a filter, the efficiency level and resistance characteristics of the filter will significantly affect the working point of the entire machine. If the same fan is equipped with different filters, the external static pressure performance may be different.
The third misunderstanding is to only look at the pressure number and not the corresponding air volume. Pressure and air volume are related, and the external static pressure usually corresponds to a specific air volume. If the air volume is not stated, comparing pressure values alone has limited meaning.
The fourth misunderstanding is to ignore the change in resistance after dust accumulation on the filter. The new filter has low resistance. After running for a period of time, the resistance increases, and the actual working point of the FFU will move in the direction of low air volume. If you only calculate based on the new filter status when selecting a model, insufficient air volume may occur later.
How to unify parameter calibers
To uniformly compare the pressure parameters of different FFU manufacturers, it is recommended to follow the following steps. First confirm the parameter type, whether it is full fan pressure or external static pressure, and whether it is bare fan data or complete machine data. Confirm the test conditions again, including the filter, filter model and efficiency level, test air volume, speed or control settings, and power supply conditions. Then confirm the measurement method, static pressure measurement location, air volume measurement method, and test environmental conditions. Finally, confirm the working point, what is the external static pressure at the target air volume, and the pressure margin after the filter accumulates dust.
If the project needs to compare the performance of FFU complete machines from different manufacturers, it is recommended that the supplier provide complete machine test data of the same caliber, rather than comparing the full pressure of one fan to the external static pressure of another. During the FFU complete machine test, Aili Industrial will make complete machine test records for parameters such as air volume, static pressure, power and noise, so as to facilitate project parties to compare under the same caliber. For complete machine configurations with different structures and control methods, please refer toDC fan filter unit understands the specific parameter expression.
Which parameters should you look at when selecting a model?
When selecting, you should look at the external static pressure, but it should be combined with the target air volume and filter status. Because the FFU will eventually be connected to the clean room air supply system, what needs to be overcome is the resistance of the external system, rather than the individual evaluation of the fan capacity. The total pressure of the fan can be used as a reference to understand the fan capacity, but it cannot directly replace the external static pressure of the entire machine for system matching.
For projects that need to overcome high external resistance, such as areas equipped with high-efficiency air supply outlets, long air supply paths, or areas with high return air resistance, focus should be placed on the external static pressure margin of the FFU under the target air volume. For ordinary circulating air supply scenarios, the external static pressure demand is relatively low, but it is still necessary to confirm the change in the operating point after dust accumulation on the filter.
If the project also has chemical filtration or other additional resistance, the external static pressure demand will further increase, and the resistance of the additional filter needs to be included in the calculation.
Issues that should be confirmed in advance during project communication
During the FFU selection and parameter comparison stage, it is recommended to confirm the following with the manufacturer: whether the pressure parameters provided are the full pressure of the fan or the static pressure outside the machine; whether the test includes a filter and what filter to use; what the test air volume and speed are; the measurement location and method of the static pressure outside the machine; how to consider the pressure margin after dust accumulation in the filter; whether the power supply conditions are consistent with the project; whether additional chemical filtration or other resistance components are required.
Only after these issues are confirmed can the FFU parameters of different manufacturers be comparable. For clean room projects, FFU is not an isolated device, and the pressure parameters must be viewed together with the complete machine, filter and system resistance.
in conclusion
FFU external static pressure and fan total pressure represent different pressure calibers. The total pressure of the fan describes the energy increment of the fan body, and the external static pressure describes the pressure capacity of the whole machine available to the external system. When selecting a model, the test conditions should be unified and it should be clear whether the filter is included, the corresponding air volume and the measurement method. The full pressure of the bare fan cannot be directly regarded as the static pressure of the whole machine that can be used by the system.
Aili Industrial has complete production capabilities in FFU complete machines and filters, and can provide air volume, static pressure and power data of the same caliber during complete machine testing to help project parties compare different solutions under unified conditions. If you are sorting out the FFU parameter comparison table, you can download it fromAili Industrial FFU fan filter unit to learn about the complete machine configuration, you can also refer toFFU is equipped with ULPA ultra-high efficiency filter to understand the impact of the filter on the working point of the whole machine.
