What is a fan box? Understand its role from air volume, static pressure and system location
The fan box is a combined device that provides air supply and exhaust power to the air duct or equipment. It installs the fan and motor in the box and connects to the air duct or equipment through the air inlet and outlet. The air flows through it to obtain the pressure required to overcome the pipeline resistance. Aili Industry is discussingWhen planning the fan box , the first thing to confirm is the design air volume, external static pressure, air supply or exhaust purpose, and power supply conditions, and then determine the combination of fan, motor, control and sheet metal structure based on this.
What is a fan box? Let’s first look at what it does in the system
The core task of the fan box is not 'how much wind to blow out', but 'to stably provide the required air volume under the resistance of the system'.
The fan box installs the fan and motor inside the box, and connects to the air duct or equipment through the air inlet and outlet. The airflow obtains energy through the impeller, which is used to overcome external resistance such as air ducts, elbows, valves and filter sections. Therefore, when discussing the fan box, you can't just ask 'how much wind it can blow', but you must also explain how much external static pressure this air volume is achieved. When the length of the air duct, the number of elbows, the opening of the valve and the status of the filter section change, the actual operating point will also move accordingly.
From the perspective of system location, the fan box mainly plays three roles in the ventilation and air conditioning system: as an air supply power source, providing pressure for the AHU or air duct system; as an exhaust device, used for clean room exhaust or maintaining indoor pressure balance; as a booster unit, connected in series in the air duct to solve the problem of insufficient air volume caused by excessive pipeline resistance.
Why do fan box air volume and static pressure have to be looked at together?
The nominal maximum air volume is mostly obtained under specific test conditions and does not necessarily correspond to the actual external static pressure of the project. When selecting a model, at least three parameters, 'air volume, external static pressure, and complete machine input power' should be written at the same time, and a performance curve should be provided if necessary. The intersection of the fan performance curve and the system resistance curve is the expected operating point.
This also means that if the same fan chassis has sufficient air volume when connected to a short air duct, but cannot meet the end requirements after being connected to a new filter section and long air duct, this is not necessarily a motor failure. As the system resistance increases, the fan operating point moves along the performance curve in the direction of small air volume, and the actual air volume delivered naturally decreases. At this time, the system resistance should be re-measured to find a new operating point on the fan performance curve, and then determine whether to optimize the air duct, adjust the fan configuration, or replace the filter section.
How to divide the work among fan box, filter, FFU and EFU?
The fan box is responsible for providing power, and it does not have high-efficiency filtration capabilities just because the name has 'box'. For systems requiring air cleanliness, the filtration level, mounting location and sealing requirements should be determined individually.
When the system end adoptsWhen using a HEPA/ULPA high-efficiency filter , the initial resistance of the filter and the resistance at the end of use should be included in the total resistance of the system. If the project requires a higher level of particulate matter control, it may also be evaluatedWhether the ULPA ultra-high efficiency filter meets the process requirements.
If the project requires direct filtering of air supply from the top of the equipment,FFU fan filter unit may be another structural option. FFU combines a fan and a high-efficiency filter, has its own power and modular installation, and is suitable for ceiling air supply in large-area clean rooms. When multiple FFUs need to be managed uniformly, they can cooperate withThe FFU computer group control system realizes centralized speed regulation and status monitoring.
If the core requirement is to protect the machine microenvironment of a single process equipment, rather than the entire clean room, thenAn equipment-side fan filter unit (EFU) may be more suitable than an FFU. EFU is specially designed for local purification at the equipment end. It is more compact and can be installed directly at the air inlet of the equipment to provide machine-level protection.
When final filtration and uniform air supply are required at the end of the air duct, you can also consider usingHigh-efficiency air supply outlet (HEPA BOX) is used as the terminal device. The division of labor boundaries between these equipment and the fan box should be clearly drawn on the system flow chart to avoid confusing power equipment and filtering equipment.
Project communication should start at the point of work
A useful fan box demand sheet should at least state the following information:
Design air volume (peak operating conditions and common operating conditions are listed separately)
External static pressure (including all resistance of filter section, coil, valve, etc.)
Air supply or exhaust purpose
Power supply conditions (voltage, frequency, whether to reserve speed adjustment interface)
continuous running time
Air outlet direction and maintenance space
Whether interlocking with building control systems or equipment is required
When Aili Industrial designs the fan, motor, control and sheet metal structure, it first determines the combination based on these working conditions, and then discusses whether speed adjustment or customized boxes are needed. Providing four pieces of information including air volume, external static pressure, running time and control interface can form an executable plan faster than just writing 'requires a fan chassis'. The specific structure and configuration options can be viewedFan box product catalog。
