Centrifugal Fan Selection Guide: Airflow, Static Pressure and Noise

Centrifugal Fan Selection Guide: Airflow, Static Pressure and Noise

Choosing a centrifugal fan comes down to matching four published numbers to the job: the air volume you need (m³/h), the total static pressure the duct system will impose (Pa), the noise level the space can tolerate (dB), and the electrical supply available on site. When more than one model can move the required air against the required resistance, the quieter and lower-power option is normally the smarter buy. A larger impeller turning slowly will usually deliver the same airflow more quietly than a small impeller running flat out.

CF-11 series low-noise centrifugal fan. Selection depends on airflow, static pressure, speed and supply.

Quick Answer: work from the airflow and the total system resistance, not from the fan size. Then look at the published speed, power and noise for a candidate duty point, check the voltage and phase you actually have, and make sure the duct connection matches. The exact model still has to be settled against the datasheet and the duct calculation.

Note: the values in this guide come from the published CF-11 series data on this site and describe that family. Confirm any specific model against its own datasheet before you order.

What a centrifugal fan is used for

A centrifugal fan pulls air in along the axis of a spinning impeller and throws it out at right angles, so pressure builds as the air moves outward. That pressure-building behaviour is exactly why centrifugal fans turn up in ducted exhaust, long runs, filter banks and any air path with real resistance. An axial fan moves more air at lower pressure. A centrifugal fan gives up some of that airflow in exchange for the ability to push against resistance.

In industrial ventilation, the jobs where we most often see centrifugal fans specified are:

• Ducted exhaust from workshops, welding areas and process rooms
• Fresh-air supply through long or fitting-heavy duct runs
• Filtration and dust-collection systems, where the fan has to overcome filter resistance
• Kitchen and commercial exhaust where a stable pressure is required

How to select a centrifugal fan in five steps

Step 1. Define the required air volume (m³/h)

Work out how much air the space needs. For general ventilation this is usually expressed as air changes per hour, so room volume multiplied by the target ACH gives the hourly air volume. For source-capture or process exhaust, the hood or capture design sets the figure. If the design condition is not final yet, write it down as a range rather than a single number.

Step 2. Estimate the system static pressure (Pa)

Add up the resistance of the entire air path: straight duct, bends, transitions, grilles, filters and any heat exchanger. Filters and long runs dominate the total. The model you pick needs a published pressure figure, at the required airflow, that covers this total. Underestimating pressure is the single most common reason a fan “runs but does not extract”.

Step 3. Match speed, power and supply

A 4-pole motor, around 1450 r/min, is quieter and generally the better choice for continuous duty. A 2-pole motor at roughly 2900 r/min gets more pressure and airflow out of a smaller impeller, but it is louder. The supply you have on site decides quite a lot here, because the model options differ between single-phase 220 V and three-phase 380 V.

Step 4. Check the sound level against the space

Published dB(A) figures are useful for comparing models, not for predicting the noise in a room. In occupied spaces, offices, clinics and residential buildings, favour the lower-speed models and plan for acoustic treatment or a remote mounting position. In a plant room or an area nobody works in, noise is usually a secondary concern behind getting the duty right.

Step 5. Verify the physical size and connection

Check the fan’s overall size, its inlet and outlet dimensions, and the duct connection against the space you have and the ductwork already in place. A model that meets the duty but will not fit the duct is not a solution.

Published CF-11 series data (reference)

The CF-11 low-noise centrifugal series runs from 0.18 kW to 4 kW across 4-pole and 2-pole variants. The table below reproduces the published values for the family so you can identify a first-pass candidate. Final selection should always reference the exact model datasheet.

Source: published CF-11 series selection data. Air volume and pressure are shown as the operating range; noise is a published upper value. These values describe the family and are not a site-specific guarantee.

Reading the table: an example

Take a workshop duct run that needs around 3,000 m³/h against roughly 600 Pa of total resistance, on a 380 V three-phase supply. Run your eye down the table. The 2.5A-4 gives 2,000 to 2,800 m³/h at 530 to 450 Pa, so the airflow is a little low. The 3A-4 covers 3,500 to 4,000 m³/h at 800 to 715 Pa on 1.5 kW. The 4A-6 offers 2,500 to 4,200 m³/h at 600 to 520 Pa on 1.1 kW, and it turns at only 960 r/min, which is attractive if noise matters. Which one is right depends on what you value more: the lowest power draw, or a wider margin on airflow. That is a decision the datasheet and the duct calculation settle together, not something a catalogue can answer on its own.

When a centrifugal fan is the wrong choice

• Very low resistance, high airflow: an axial or mixed-flow fan usually moves more air per watt. The inline duct fan hub covers the ducted, lower-pressure duties.
• Silence is the dominant requirement: in an occupied space a large low-speed axial or mixed-flow fan can be a better answer than a small high-speed centrifugal unit.
• Explosive or corrosive airstreams: standard models are not specified for these. Material and motor protection have to be confirmed for the application.

Frequently asked questions

How do I know which airflow value to use?

Use the design airflow from the ventilation calculation or the capture hood specification. If the design is not final, size on the upper end of the range. A fan that only just meets the duty has no margin left for a dirty filter or one more bend.

Is a higher-speed fan always more powerful?

No. Speed raises the pressure a given impeller can produce, and it raises the noise at the same time. A larger impeller at lower speed can deliver the same airflow with less noise and comparable power, which is why 4-pole and 6-pole models are so common where noise matters.

Can Linggongshare recommend the exact model?

Yes. Once we know the airflow, static pressure, supply and available space, we can shortlist candidates from the published family data. The final model still has to be confirmed against its datasheet and your duct calculation.

Are the table values final for ordering?

They are published reference values for the family. For ordering, the exact model’s nameplate data and your project condition govern. The CF-11 series product page has the full selection snapshot.

Plan your ventilation project with Linggongshare

Linggongshare supplies duct fans, centrifugal fans, exhaust fans, air curtains, dehumidifiers and heaters for industrial and commercial ventilation. To request a quote, send us the required airflow, static pressure, supply voltage, duct size and destination market. Browse the full product selection hub or the inline duct fan hub, or contact us and we will help you narrow it down.

Published 11 September 2026. Reviewed against the published CF-11 series data.