When I talk with customers about an air supply fan, I usually ask one simple question first: what kind of airflow do you actually need? In my experience, this is much more important than simply choosing a fan by motor power or fan size.

A ventilation system may look simple from the outside, but the working conditions can be very different from one project to another. A factory workshop, a commercial building, an air conditioning system, and an industrial production line can all need air supply, yet their airflow, pressure, temperature, installation space, and running time may be completely different.

Our Constant-Load Double-Inlet Air Supply Fan is developed for applications that require steady and dependable air delivery. The double-inlet structure allows air to enter from both sides of the fan, while the overall fan configuration can be matched to the required airflow, pressure, motor power, and installation conditions.

At Zhejiang Shangyang Industrial Fan Co., Ltd., we have around 20 years of experience in industrial fan design, manufacturing, and sales. Our sales company is located in Shanghai, China, and our manufacturing facility is located at No. 6-8, Bifa Road, Xinbi Subdistrict, Jinyun County, Lishui City, Zhejiang Province.

Over the years, I have worked with different types of industrial fan applications. Our factory manufactures Centrifugal Fans, High-Temperature Fans, induced draft fans, axial fans, Low-Noise Centrifugal Fans, High-Pressure Fans, stainless steel centrifugal fans, hot air circulating fans, mixing fans, explosion-proof centrifugal fans, and other standard and non-standard industrial fans.

This background is useful when we design an air supply fan because we do not look at the fan as an isolated machine. We look at how the fan will work with the duct, filter, air conditioning equipment, workshop, production line, or other equipment around it.

1. What Is a Constant-Load Double-Inlet Air Supply Fan?

A Constant-Load Double-Inlet Air Supply Fan is an industrial air-moving fan designed to deliver air steadily into an HVAC, air conditioning, or industrial ventilation system. Its double-inlet structure allows air to enter the impeller from two sides, which can provide a practical solution for applications requiring relatively large air volumes.

The phrase “constant-load” is important, but I want to explain it in plain language.

In an actual ventilation system, the fan does not work alone. It must push air through ducts, filters, grilles, dampers, heat exchangers, air handling equipment, and other components. These components create resistance. The fan must provide enough pressure to overcome that resistance while delivering the required air volume.

So when we configure a constant-load air supply fan, we pay attention to the actual operating point rather than simply saying that a larger motor is always better.

A larger motor can consume more electricity, increase equipment cost, and may not solve an incorrectly designed airflow system. On the other hand, a fan that is too small may not deliver enough air when the system is operating under its real resistance.

That is why our first step is always technical confirmation.

Double-Inlet Design

In a conventional single-inlet fan, air enters the impeller from one side. A double-inlet fan allows air to enter from both sides of the impeller.

This structure is commonly used where relatively high air volume is required and where the installation layout is suitable for a double-inlet arrangement.

For large HVAC systems and industrial air supply applications, this can be a useful design choice.

However, I do not recommend selecting a double-inlet fan just because it sounds more powerful. The inlet arrangement, duct layout, pressure requirement, installation space, and required airflow still need to be checked.

Air Supply Instead of Exhaust

Another point worth understanding is the difference between supply and exhaust.

An exhaust fan removes air from a space. An air supply fan pushes or delivers air into a space or process system.

In many industrial projects, both are needed. For example, a workshop may use a supply fan to bring fresh or conditioned air into the building while another fan removes warm, dusty, or contaminated air.

Good ventilation is often about maintaining a planned air balance rather than simply moving as much air as possible.

2. How the Double-Inlet Air Supply Fan Works

The working principle is straightforward.

When the motor starts, it drives the impeller to rotate. As the impeller rotates, it draws air through the two inlet sides. The blades then move the air toward the outer part of the fan casing. The casing guides the air toward the outlet, where it enters the connected duct or air distribution system.

The motor provides the mechanical energy, while the impeller and casing control the movement of air.

That sounds simple, but getting good results requires the fan to be matched with the system.

Air Volume

Air volume tells us how much air the fan needs to move over a certain period.

Depending on the market and project, customers may provide the requirement in cubic meters per hour, cubic meters per second, or cubic feet per minute.

We can work with different units as long as the required operating condition is clear.

Static Pressure

Pressure is equally important.

Imagine trying to blow air through a short, wide pipe. It is relatively easy. Now imagine pushing the same amount of air through a long duct with many bends, filters and dampers. The resistance is much greater.

The fan needs enough pressure to overcome this resistance.

This is why I always ask customers for duct length, duct size, elbows, filters, dampers and other connected equipment when the pressure requirement is not already available.

Motor Power

Motor power is selected according to the fan operating condition.

We also confirm voltage, frequency, motor speed and other electrical requirements. This is especially important for overseas customers because electrical standards can differ between countries and regions.

Fan Speed

Fan speed affects airflow, pressure, noise, and power consumption.

For this reason, fan speed should not be changed casually after installation. If the customer needs variable airflow, we can discuss a suitable control arrangement during the design stage.

Air Temperature

For normal air conditioning applications, the air temperature is usually not particularly demanding. Industrial processes can be different.

If the fan will handle hot air, process air, or air from a heated production system, we need the normal and maximum operating temperatures before selecting the configuration.

Source: Zhejiang Shangyang Industrial Fan Co., Ltd. fan selection and engineering communication practice. Actual values depend on the customer's ventilation system and operating conditions.

3. Main Features of Our Constant-Load Double-Inlet Air Supply Fan

When I design or recommend an industrial fan, I prefer useful features over fancy descriptions. A fan installed in a factory or HVAC system has to run in the real world. It needs to deliver air, handle its working load, fit the available space, and remain practical to maintain.

Stable Air Supply

The main purpose of this fan is steady air delivery.

We select the fan according to the required airflow and pressure so that the fan can work properly with the customer's system.

This is particularly important for air conditioning and industrial ventilation systems where unstable airflow can affect temperature distribution, ventilation quality, or production conditions.

Double-Inlet Air Intake

The double-inlet structure allows air to enter from both sides of the impeller.

For suitable applications, this provides an efficient way to handle larger airflow requirements without relying on an oversized single-inlet arrangement.

Industrial Construction

Industrial fans need to be stronger than ordinary household ventilation equipment.

Our factory manufactures fans for workshops, coating equipment, boilers, kilns, environmental protection systems, thermal energy equipment, printing systems, chemical applications, food processing, and other industrial environments.

The exact material and construction depend on the application.

Flexible Configuration

We can discuss different airflow, pressure, motor, rotation speed, material and installation requirements.

This makes the fan suitable for both standard projects and non-standard industrial applications.

Low-Vibration Operation

Vibration is one of those problems that may seem small during installation but becomes annoying after months of operation.

It can come from poor balance, incorrect assembly, bearing problems, loose fasteners, unsuitable foundations, or other factors.

During production, we pay attention to the rotating assembly and mechanical condition of the fan.

Convenient Maintenance

Regular maintenance is still necessary, even when the fan has a reliable structure.

We recommend checking the motor, bearings, fasteners, rotating assembly, electrical connections, inlet and outlet passages, and other relevant components according to the operating environment.

A simple inspection schedule can prevent many avoidable problems.

4. Direct-Drive, Belt-Drive and Double-Inlet Fan Structures

Customers sometimes compare different fan structures based only on the name. I think it is better to compare what each structure is actually designed to do.

For example, a double-inlet fan describes the air intake arrangement. Direct drive and belt drive describe the power transmission arrangement. These are not necessarily mutually exclusive concepts.

A double-inlet fan can be configured with different drive arrangements depending on the specific design.

Source: General centrifugal fan engineering principles and Zhejiang Shangyang Industrial Fan Co., Ltd. product design practice. This comparison is structural rather than a universal performance ranking.

Direct Drive vs. Belt Drive

If a direct-drive arrangement is used, the motor is connected directly to the fan rotating assembly. This can simplify the mechanical transmission system.

A belt-drive arrangement uses belts and pulleys between the motor and fan shaft. It can offer useful flexibility in certain applications, especially where speed adjustment through pulley ratios or a different motor position is required.

Neither structure is automatically better for every project.

For a normal-temperature air supply application with suitable installation conditions, direct drive can be attractive because of its simple transmission structure. For other industrial applications, belt drive may make more sense.

Source: General industrial fan transmission principles and Zhejiang Shangyang Industrial Fan Co., Ltd. engineering practice. Final drive selection depends on operating temperature, fan duty, installation requirements and customer specifications.

5. Where Is the Constant-Load Double-Inlet Air Supply Fan Used?

Our air supply fans are used in a wide range of ventilation and industrial applications. The common point is the need for controlled and dependable air delivery.

HVAC Systems

Heating, ventilation and air conditioning systems need fans to move air through ducts and equipment.

Our Constant-Load Double-Inlet Air Supply Fan can be configured for air supply duties where the required airflow and pressure match the fan's operating range.

Commercial Buildings

Large buildings such as hotels, shopping centers, office buildings and public facilities may require centralized ventilation and air conditioning.

For these projects, stable air supply is important for distributing conditioned air through the building.

Factories and Workshops

Industrial workshops often have larger ventilation requirements than ordinary buildings.

Heat from machines, production processes, people, and lighting can affect the indoor environment. Air supply fans can form part of the overall ventilation system.

Industrial Production Lines

Some production lines require controlled air movement around machines or process equipment.

In these applications, the fan must be selected according to the actual process conditions rather than simply the room size.

Air Handling Equipment

The fan can also be used as part of an air handling system where air needs to pass through filters, coils, ducts, dampers or other equipment.

In such systems, pressure loss needs to be considered carefully.

Printing and Coating Equipment

Our company has experience in fans used for printing and coating-related equipment.

Different parts of these systems may require air supply, exhaust or process air circulation. The fan configuration needs to match the actual role of the equipment.

Thermal Energy and Industrial Equipment

Our broader product range also covers hot air circulating fans and high-temperature fans.

If the customer's air supply application involves elevated temperatures, we can review whether a standard air supply fan is appropriate or whether a high-temperature fan should be considered.

Source: Zhejiang Shangyang Industrial Fan Co., Ltd. application information and manufacturing experience. Actual suitability must be evaluated according to the specific project.

6. How We Manufacture the Fan

For an industrial fan, manufacturing quality starts before the first piece of metal is processed.

Our first step is understanding the customer's requirements.

Technical Review

We first confirm the required air volume, static pressure, motor power, rotation speed, air temperature and installation dimensions.

If the customer has an existing system, we also want to understand the duct layout and connected equipment.

This information helps us avoid selecting a fan based on only one number.

Fan Design

After the operating condition is confirmed, the engineering team determines the suitable fan structure.

For a double-inlet fan, the impeller, inlet arrangement, casing, outlet and drive configuration all need to work together.

Material Preparation

We select materials according to the application.

For normal air supply systems, conventional industrial Fan Materials may be suitable. For corrosive or demanding environments, stainless steel or other suitable material options can be discussed.

I do not recommend choosing a more expensive material without a real reason. Material selection should be based on the actual air characteristics, temperature and operating environment.

Impeller Production

The impeller is one of the most important parts of the fan.

Its shape, blade arrangement, dimensions and balance all affect the fan's operating condition.

After assembly, the rotating components are checked to reduce problems caused by imbalance or poor mechanical assembly.

Casing Manufacturing

The fan casing creates the air passage around the impeller and guides the moving air toward the outlet.

Correct dimensions and proper assembly are important for maintaining the intended airflow path.

Motor Assembly

The motor is installed according to the confirmed configuration.

For overseas projects, we confirm electrical requirements such as voltage and frequency before production.

Inspection and Final Preparation

Before shipment, we inspect the relevant dimensions, assembly condition, motor configuration, rotating components, accessories and other agreed requirements.

Our company also has multiple national test reports for specialized products and has obtained applicable certifications including national explosion-proof certification and energy efficiency certification for relevant products.

7. Production Time, Delivery, Payment, Transportation and Packaging

When buying an industrial fan, customers often care about more than technical specifications. They also want to know when the product will be ready, how it will be shipped, and what will be included in the delivery.

Production Cycle

The typical production cycle for our air supply fan products is approximately 7–20 working days.

This is a general reference rather than a fixed promise for every order.

Production time depends on the fan model, airflow requirement, pressure, motor, material, customization, order quantity, and current production schedule.

Delivery Standard

Standard delivery normally includes the complete fan unit, motor, and agreed accessories according to the final technical specification.

If the customer requires additional components, special flanges, control equipment, flexible connectors or other accessories, these can be discussed before production.

Payment Terms

Payment arrangements can be confirmed according to the order and commercial agreement.

A common arrangement is a deposit before production and the balance before shipment.

For customized equipment, we recommend confirming the complete technical and commercial details before making the production deposit.

Transportation

For domestic orders, road freight is commonly used.

For overseas customers, sea freight is often suitable for larger industrial ventilation equipment. Depending on destination and delivery requirements, other logistics solutions can also be considered.

Packaging

We select packaging according to the fan size, structure and transportation conditions.

Common packaging options include protective film, reinforced cartons, wooden frames and wooden cases.

For long-distance transportation, especially overseas shipments, suitable wooden protection helps reduce the risk of impact, movement, moisture and handling damage.

Source: Zhejiang Shangyang Industrial Fan Co., Ltd. supplied product and order information. Lead time, payment, packaging, accessories and logistics are subject to the final quotation and purchase agreement.

8. Why Work With Zhejiang Shangyang Industrial Fan Co., Ltd.?

I know that every industrial fan manufacturer can say that its products are reliable. Instead of repeating the same marketing language, I would rather explain what we actually do.

Our company has been involved in industrial fan technology, manufacturing and sales for around 20 years.

Our factory specializes in standard and non-standard industrial fans. This means that our work is not limited to one fixed model or one application.

We have experience with centrifugal fans, high-temperature fans, induced draft fans, axial fans, low-noise centrifugal fans, high-pressure fans, stainless steel centrifugal fans, hot air circulating fans, mixing fans and explosion-proof centrifugal fans.

Experience With Different Industries

Our fans are used in coating, kiln, boiler, environmental protection and dust collection, thermal energy, printing, coating equipment, medical latex equipment, air-supported membrane, separation, cement, chemical and food industries.

Each industry presents different problems.

A chemical plant may care about corrosion. A kiln system may care about high temperature. A commercial HVAC system may care more about stable airflow, noise and installation. A dust collection system has different requirements again.

Working across these applications has helped us build a broader understanding of industrial air movement.

Long-Term Product Improvement

Our coating fan and environmental protection fan development began with technical experience from Taiwan, followed by more than a decade of continuous improvement, refinement and optimization.

We have not treated the fan as a product that can be designed once and never changed. Actual operating conditions provide useful feedback, and we continue to improve the design and manufacturing process based on customer requirements.

Testing and Certification

We possess multiple national test reports for specialized products and have successively obtained national explosion-proof certification, energy efficiency certification and other applicable certifications.

For a project that requires certification, I recommend confirming the exact product model and certification requirements before ordering. A certification should always be matched to the relevant product and configuration.

Technical Communication Before Production

One thing we take seriously is communication before manufacturing.

If a customer gives us only “30,000 m³/h air volume,” I will not consider the selection complete.

I want to know the pressure, temperature, duct arrangement, installation position, air characteristics, motor requirements and other important information.

This takes a little more time at the beginning, but it can prevent much bigger problems later.

9. What Should You Tell Us Before Ordering?

If you are looking for a double-inlet Industrial Air Supply Fan, you do not need to prepare a complicated technical report before contacting us. Even basic information can help us start the discussion.

I normally recommend preparing the following:

• Required air volume

• Required static pressure

• Air temperature

• Air characteristics

• Fan installation location

• Inlet and outlet dimensions

• Motor voltage

• Power frequency

• Required motor power, if already specified

• Expected operating hours

• Quantity required

• Special material or certification requirements

If you already have a fan drawing or equipment specification, sending it to us can make the technical discussion much easier.

If you do not know the pressure, that is not necessarily a problem. We can review the duct and equipment information and discuss how the pressure requirement can be determined.

10. Frequently Asked Questions About Constant-Load Double-Inlet Air Supply Fans

Q1: What is a Constant-Load Double-Inlet Air Supply Fan?

It is an industrial air supply fan designed to provide stable airflow for HVAC, air conditioning and industrial ventilation systems. The double-inlet structure allows air to enter the fan from both sides of the impeller.

Q2: What is the advantage of a double-inlet design?

A double-inlet arrangement allows air to enter from both sides of the impeller. It is commonly considered for applications requiring relatively large air volumes and a suitable installation layout.

Q3: Can this fan be used in an HVAC system?

Yes. It can be configured for suitable HVAC and air conditioning air supply applications according to the required airflow, pressure, temperature, motor specification and installation conditions.

Q4: Can the fan be customized?

Yes. We manufacture both standard and non-standard industrial fans. Airflow, pressure, motor power, rotation speed, materials, dimensions and other requirements can be discussed according to the project.

Q5: Is this fan suitable for factories?

Yes. It can be used for factory and workshop air supply where the fan's operating range matches the ventilation requirements.

Q6: What is the difference between an air supply fan and an exhaust fan?

An air supply fan delivers air into a space or process system, while an exhaust fan removes air from the space or process. A complete ventilation system may use both.

Q7: How do I select the correct fan size?

The most important information is required air volume and pressure. Temperature, air characteristics, motor requirements and installation dimensions should also be considered.

Q8: Can you provide stainless steel construction?

Yes. We manufacture stainless steel centrifugal fans. Where the application requires improved corrosion resistance, stainless steel or another suitable material can be considered.

Q9: Can the fan operate continuously?

The fan can be configured for continuous industrial operation when the selected model, motor and working conditions are suitable. Continuous operation requirements should be confirmed before production.

Q10: What is the normal production lead time?

The typical production cycle is around 7–20 working days. The actual lead time depends on the model, specifications, customization, materials and order quantity.

Q11: What payment terms do you accept?

Payment terms can be arranged according to the order agreement. A common arrangement is a deposit before production and the balance before shipment.

Q12: How is the fan packaged?

Depending on the product size and transportation method, we normally use protective film, reinforced cartons, wooden frames or wooden cases.

Q13: Can you ship the fan overseas?

Yes. Our industrial fans are sold throughout China and exported overseas as supporting equipment. Sea freight and other suitable logistics solutions can be considered according to the destination.

Q14: Do you provide explosion-proof industrial fans?

Yes. Our factory manufactures explosion-proof centrifugal fans and applicable products have obtained national explosion-proof certification. For hazardous-area applications, the exact operating conditions and certification requirements must be confirmed.

11. My Practical Advice When Choosing an Industrial Air Supply Fan

After years of working with industrial fans, I have learned that the cheapest fan is not necessarily the cheapest solution.

The real cost comes from the entire operating period.

If a fan cannot deliver the required air volume, the ventilation system may not work as expected. If the motor is oversized, unnecessary energy may be consumed. If the fan does not fit the installation space, additional modification work may be needed. If the material is unsuitable for the air conditions, maintenance can become a headache.

So I always recommend matching the fan to the real application first.

For a Constant-Load Double-Inlet Air Supply Fan, start with air volume and pressure. Then consider temperature, air characteristics, installation dimensions, motor requirements and operating hours.

If the project is part of a larger HVAC or industrial ventilation system, we also need to consider the connected equipment. Filters, ducts, dampers, heat exchangers and other components all affect the final fan operating point.

There is no value in selecting a fan based on one attractive specification if the complete system does not match it.

12. Conclusion

Our Constant-Load Double-Inlet Air Supply Fan is designed for customers who need stable air delivery in HVAC, air conditioning, factory ventilation and industrial air supply applications.

The double-inlet structure provides air intake from both sides of the impeller, while the fan can be configured according to airflow, pressure, motor power, speed, temperature, materials and installation requirements.

We manufacture standard and non-standard industrial fans at our factory in Zhejiang, China. With around 20 years of experience in industrial fan design, manufacturing and sales, we have developed products for coating, environmental protection, dust collection, thermal energy, printing, chemical, food, cement and other applications.

Our approach is simple: understand the customer's working condition first, select the fan according to the actual system, manufacture it according to the agreed specification, and provide suitable packaging and delivery arrangements.

If you are sourcing a Constant-Load Double-Inlet Air Supply Fan for an HVAC system, factory, workshop, commercial building or industrial project, you can send us your required airflow, pressure, temperature, motor requirements and installation dimensions. If some information is not available, send us the available drawings or system details, and we can start from there.

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Product and company information source: Zhejiang Shangyang Industrial Fan Co., Ltd. company and product information supplied for this page. Technical values, production lead time, payment terms, delivery contents, transportation and packaging arrangements are general references and should be confirmed in the final technical quotation and purchase agreement. Fan performance depends on actual airflow, pressure, temperature, air characteristics, installation conditions and system design.