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How do You Control the Pressure of a Centrifugal Fan?

Pressure control in centrifugal fans and blowers is crucial for…

How do You Control the Pressure of a Centrifugal Fan?

Pressure control in centrifugal fans and blowers is crucial for optimising performance and efficiency in industrial, HVAC, and ventilation applications. Traditional pressure control methods include using fixed-speed motors with dampers, resulting in overall energy wastage and increased wear and tear on components. How, then, do you control a centrifugal fan or blower’s pressure?

Popular techniques for controlling pressure in centrifugal fans and blowers include adjusting the fan speed, adjusting system resistance, and using control dampers or indirect drives. Using these techniques helps to create an efficient system that meets the pressure demands of a specific system.

The benefits of proper pressure management in centrifugal blower fans include energy conservation, enhanced equipment longevity, and adherence to pertinent safety standards. In this article, we’ll explore in greater depth how engineers, technicians, and operators can accurately manage the pressure of centrifugal fans for different applications.

Understanding Fan Speed Adjustments: The Role of RPM in Pressure Control

Secomak Fans & Blowers

Understanding and managing fan speed is essential for engineers and technicians looking to achieve the desired pressure output in specific centrifugal blower applications. Additionally, finding and maintaining the ideal fan speed is helpful in optimising performance in various industrial, HVAC, and ventilation systems.

A centrifugal blower fan’s speed directly affects its pressure output. Since the fan rotates on an axis, its speed is gauged in revolutions per minute (RPM). By varying the RPM, the blower’s impeller (which generates the airflow) spins faster or slower, directly influencing the pressure.

Here’s how it works:

  • When a centrifugal fan’s RPM increases, the impellor rotates faster, causing the blower to draw in more air and generate higher pressure.
  • Conversely, reducing the fan’s RPM slows the impellor, decreasing airflow and lowering pressure output.

This relationship between RPM and pressure is fundamental to adjusting the blower’s performance to meet specific system requirements. Additionally, finding the most efficient RPM for a centrifugal blower is essential to reducing operational costs.

Controlling RPM is achievable through devices like Variable Frequency Drives (VFDs). VFDs allow for precise adjustment and regulation of the blower speed, enabling operators to fine-tune the pressure output according to the application’s demands.

System Resistance: Its Impact on Centrifugal Fan Pressure

High Velocity Fan and High Velocity Centrifugal Blower

System resistance significantly affects the pressure output of a centrifugal fan. Effectively, resistance creates a pressure drop that opposes the fan’s airflow and reduces pressure. For example, as a fan operates, it must overcome the resistance created by various components within the system, e.g., ductwork, filters, dampers, and other obstructions.

The total pressure developed by a centrifugal fan comprises two components: static pressure and dynamic pressure. Static pressure is the friction (resistance to airflow) caused by air moving through elements such as hoses, ducts, louvres, hood slots, etc. In contrast, dynamic pressure results solely from the airflow’s velocity. System resistance primarily impacts static pressure.

When system resistance increases due to clogged filters, longer ducts, or partially closed dampers, the fan must work harder to maintain the desired airflow. Consequently, the fan must generate a higher static pressure to overcome the increased resistance. To achieve a higher static pressure, the fan must have a more powerful impellor or spin faster, consuming more energy in the process.

Understanding and minimising system resistance is crucial for optimising centrifugal fans’ performance. Ways to reduce resistance include the following options:

  • Proper or improved system design,
  • Regular maintenance and cleaning of components, and
  • Selecting appropriate fan sizes.

These help to ensure the fan operates efficiently and meets the application’s pressure requirements while minimising energy consumption. Engineers must carefully analyse and account for system resistance when designing effective systems with optimal fan performance.

VFDs (Indirect Drives): Revolutionising Pressure Control in Centrifugal Blowers

High Velocity Fan and High Velocity Centrifugal Blower

VFDs and indirect drives have revolutionised pressure control in centrifugal blowers by providing precise and efficient fan speed management. Traditional methods of pressure control involved using direct drives (or fixed-speed motors) and dampers to regulate airflow. These systems were less energy-efficient and often wasted energy.

VFDs have transformed this scenario in several ways:

  • Precise control speed: VFDs allow for fine-tuning the blower’s motor speed, enabling operators to adjust the fan’s RPM with exceptional precision. Precise control over fan speed directly translates into accurate pressure control. This means blowers can operate at the exact speed to meet the system’s pressure demands while eliminating energy wastage.
  • Energy efficiency: VFDs significantly enhance energy efficiency due to their variable speed controls. Since traditional fixed-speed motors run at a constant speed, they consume a consistent amount of energy regardless of the actual demand. Conversely, VFDs vary motor speed according to real-time requirements, minimising energy wastage and reducing operational costs.
  • Soft start and stop: VFDs allow for gradual acceleration and deceleration of the blower, eliminating sudden voltage spikes and mechanical stress during startup and shutdown. This feature prolongs the equipment’s lifespan, reducing wear and tear and maintenance costs.
  • Optimised system performance: VFDs enable centrifugal blowers to adapt the blower’s motor speed in real time according to fluctuating pressure requirements. This adaptability enhances overall system performance and responsiveness.

A prime example of Secomak’s innovative use of VFD technology is exemplified in our work with the Jordans & Ryvita Company. Secomak’s F.R.E.D. (Flexible Reliable Efficient Drying) machine played a pivotal role. At Jordans & Ryvita, the F.R.E.D. system was implemented to enhance the drying process of their cereal production line. Utilising inverter control, the F.R.E.D. machine allowed Jordans & Ryvita to achieve not only significant energy savings but also to ensure efficient and consistent drying performance. This use case highlights

Secomak’s ability to provide tailored solutions that meet specific industrial needs, focusing on energy efficiency, performance, and adaptability, which are crucial in modern production environments.

Exploring the Functionality of Control Dampers in Pressure Management

High Velocity Fan and High Velocity Centrifugal Blower

Control dampers are adjustable plates or valves placed within ductwork and ventilation systems. They are essential components in various HVAC, industrial, and ventilation systems and are vital in pressure management. The primary role of control dampers is to regulate the airflow by controlling the amount of air that passes through the ducts, which, in turn, affects the system’s pressure.

These are how control dampers function in pressure management:

Airflow Control

Control dampers are adjustable to either restrict or allow airflow within the ducts. I.e., they can be partially opened or closed to control the volume of air that flows through, consequently affecting the pressure. Partially closing the damper increases resistance, leading to higher pressure, while opening it lowers pressure because of the reduced resistance.

Balancing of Systems

Control dampers help balance airflow in the different sections of a ventilation or HVAC system. Balanced airflow is crucial for efficient operation and comfort in industrial and commercial spaces. Engineers can ensure an even airflow distribution through strategic damper adjustment, which maintains consistent pressure throughout the system.

Energy Efficiency

Properly adjusted control dampers contribute significantly to the energy efficiency of a system. By fine-tuning the airflow, ventilation systems can operate at optimal pressure levels, reducing energy consumption. This is also important in applications requiring precise pressure control, like clean rooms and laboratories.


Control dampers are commonly used in zoned HVAC systems to direct airflow where needed most. This allows for customised temperature and pressure control in different areas and enhances comfort and energy efficiency.

Maintenance and Safety

Dampers play a role in system maintenance and safety. For instance, they can be closed to isolate sections of the system for maintenance or emergency situations, e.g., preventing smoke and fire spreading in the case of a fire outbreak.

Safety & Efficiency: The Importance of Accurate Pressure Control in Centrifugal Fans

Compared side by side a direct drive fan

Accurate pressure control in centrifugal fans and blowers promotes safety and efficiency in various applications. Maintaining precise pressure levels is critical for energy efficiency as it allows fans to operate at optimal points while reducing overall energy consumption. Such efficiency leads to significant cost savings and promotes environmental sustainability.

Additionally, accurate pressure control ensures entire systems – regardless of the application or space – function as intended. Ideal pressure levels directly impact system performance by enhancing productivity and maintaining a safe environment.

Furthermore, maintaining optimal pressure levels prolongs the centrifugal blower’s lifespan by reducing wear and tear and the associated maintenance costs and downtime. Accurate pressure control also helps by facilitating compliance with regulatory standards, enabling businesses to operate responsibly and within legal frameworks.


In conclusion, accurate pressure control in centrifugal fans and blowers promotes operational efficiency and the safety and longevity of the equipment. Precise pressure management is possible by leveraging and combining control techniques, including VFDs and indirect drives, to control RPMs and employing control dampers within the system.

Secomak’s industrial fans and blowers offer industries the flexibility and ability to control the pressure within these systems according to their application’s specific requirements. With a system design tailored to your needs, you can expect optimal performance and significant energy savings, amongst other benefits.

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