8 December 2023
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When Choosing a Fan…

What Should Be Considered While Choosing a Fan?

Among hundreds of products, you can often find it difficult to find the right fan depending on your usage area and needs. Moreover, it is not at all understandable for someone who does not know the graphics in the statements of the fans. No problem! In this blog post, we will explain the things to consider when choosing a fan in its simplest form.

In our previous blog post, we talked about the fan and its usage areas. To remind you, fans are devices that provide air flow by creating a pressure difference. They work by sucking from the engine part and blowing from the propeller part. There are two types of fans, axial and radial.

While selecting the fan, 4 parameters should be considered.

  • Required air flow
  • Pressure losses
  • Acceptable sound level
  • Electrical power connection type

Air exchange required for the environment to be ventilated; The purpose of use of the environment is related to the numbers and activities of living things and things in it. Required air exchange coefficients for different environments are given in the side table.

What size fan do I need?


In line with the information given above, the required air flow is determined as follows.

Q [ m3 / hour ] = Air exchange coefficient (1 hour) * Ambient volume (m3 )


Q [ m3 / hour ] = Number of people * required airflow per person

After determining the required air flow in the environment, appropriate duct design (taking into account sound and air velocity criteria) should be made and pressure losses should be calculated. The fan type (axial, radial, roof, smoke evacuation, etc.) should be decided depending on the environment in which the fan will operate, and the appropriate fan should be selected on the curve according to the determined flow-static pressure pair.

If we briefly explain what is written above and what is in the table with an example;

5 people work in an office. If the ceiling height is 2.6 meters and the floor area is 50 m2, it has a volume of 2.6 * 50 = 130 m3. The value given for the office in the air exchange coefficient table was 4-8. Let’s take the mean as 5. 

130*5=650 m3 /h air is needed. If we accept that the office works with normal activity, a total of 650 + 145 = 795 m3 / hour air need arises for 5 people * 29 m3 = 145 m3 air requirement.

Fan selection is also made according to this flow requirement.

After making the flow calculations, the area where the fan will be mounted should be determined. Where will the fan be installed? Like ceiling, wall, chimney or vent pipe.

Another issue is the voltage of the electricity to be connected to the fan. Since we are based on the office in our example, let’s proceed from there. Fans are usually mounted on the wall or glass in offices. Since household electricity will be used, a single-phase fan should be preferred.

In other words, I need a fan with a flow rate of 795 m3 / hour that I can mount axial, monophase, glass or wall. Let’s examine the graphics under the products.

When I evaluate these two images, I first have to decide whether it is a wall type or a window type. Suppose we chose a wall-mounted fan. The air flow I needed was 650 + 145 = 795 m3/hour. In this context, the most suitable fan for me would be the D-25 model with a flow rate of 800 m3/hour.

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