Diagonal fan

What is a diagonal fan?

Diagonal fans combine the advantages of axial and radial fans. The air is not guided exclusively along the motor axis (axial) or perpendicular to it (radial), but is transported through the impeller at an oblique angle—i.e., diagonally. This diagonal flow is created by the conical housing shape and the specially shaped fan blades, whose diameter increases toward the pressure side.

There are two main types

Axial diagonal fans

These are similar to axial fans, but their conical geometry provides higher pressure and high volume flow at the same time. Our W series and DV series are typical examples of this design, equipped with EC or DC motors and wall rings made of die-cast aluminum or GRP.

Radial diagonal fans

This design combines the pressure stability of radial fans with the air performance of axial models. The diagonal airflow ensures even air distribution and reduces the formation of thermal hotspots, which increases the service life of the components. The K series is an example of this design, with a modular structure featuring an inlet nozzle and mounting plate.

What is the difference between a
diagonal panel fan and a compact diagonal fan?

Diagonal fan

They usually refer to larger, industrially used machines with a modular design. They are designed for HVAC systems, door air curtains, or fan coil units and feature conical housings, wall rings, and are equipped with EC, DC, or AC motors.

Diagonal compact fan

They are usually compact units for electronics cooling or smaller applications. The motor is integrated directly into the fan wheel. These devices offer precise volume flow control, PWM control, and are available in various protection classes. They are particularly suitable for applications with limited installation space and high controllability requirements.

In short:
The diagonal panel fan is the industrial version with a modular design, while the diagonal compact fan is a compact solution for smaller applications.

What the Tech:
How is a fan constructed?

What are the advantages of a diagonal fan?

Diagonal fans have many technical advantages that make them great for demanding applications:

  • High pressure with compact dimensions
    The diagonal flow pattern generates higher pressure than axial fans of comparable dimensions. This allows diagonal fans to be used in environments with space constraints without any loss of performance.
  • Efficient air delivery at medium back pressure
    Diagonal fans are ideal for applications where axial fans can’t handle the counterpressure, and the airflow delivered by radial fans is too low. The diagonal design offers a stable characteristic curve in the medium pressure range.
  • Uniform flow and hotspot prevention
    The diagonal flow ensures homogeneous air distribution and prevents local overheating (hot spots), which reduces thermal stress and increases service life
  • Quiet operation thanks to optimized aeroacoustics
    Thanks to their conical housing shape and flow-optimized impellers, diagonal fans are particularly quiet. This is a significant advantage in noise-sensitive environments such as office buildings or hospitals.
  • Durability and maintenance-free operation
    The robust construction, especially in radial designs (e.g., K series), enables maintenance-free operation over long periods of time. This greatly reduces life cycle costs.

FAQ – Frequently asked questions
about diagonal fans

Diagonal fans combine axial and radial airflow directions. They offer more pressure than axial fans and deliver greater volumes of air than radial fans. They are typically used in the medium pressure range.

While axial fans convey air parallel to the motor axis and radial fans deflect it by 90°, the diagonal fan generates an oblique flow due to its conical housing shape. This results in an optimized compromise between pressure increase and air performance.

There are axial and radial designs. Axial variants have conical housings and wall rings, while radial variants have a modular design with an inlet nozzle and mounting plate.

The W series and DV series represent the axial design with EC or DC motors and aerodynamically optimized impellers. The K series represents the radial design and features a robust plastic construction that allows for uncompromising aeroacoustic design. Both designs can be combined with different motor technologies and can be flexibly integrated into different applications.

A diagonal flow ensures even air distribution, reduces hot spots, and improves thermal stability, which increases service life and boosts efficiency.

The slanted outlet angle (typically between 20° and 70°) not only distributes the air more efficiently but also dissipates it with less turbulence. This results in a more stable operating point, especially under changing pressure conditions, and enables precise adaptation to the requirements of modern HVAC and electronics applications.

Diagonal fans are available with EC, DC, and AC motors.

EC motors offer the highest efficiency and controllability, via PWM, 0–10 V, or bus interfaces. Variants with integrated electronics are also available. The motors can be designed as internal or external rotors. External rotor motors enable a compact design, as the impeller is mounted directly on the rotor.

EC motors are characterized by their electronic commutation, which allows precise control of the volume flow and high energy efficiency without the use of rare earths, as ferrite magnets are used.

The diagonal flow ensures uniform airflow, reduces thermal stress, and improves efficiency. This increases the service life of the components.

Thanks to their optimized aeroacoustic design, diagonal fans are fairly quiet. The radial versions are specially designed for noise-sensitive environments.

The conical housing shape and flow-optimized impellers minimize turbulence and resonance. In combination with EC motors, which enable smooth speed control, the sound pressure level is significantly reduced. This makes diagonal fans ideal for applications in office buildings, hospitals, or high-quality industrial facilities.

The conical housing ensures that the diameter increases towards the pressure side, which supports the pressure increase and at the same time distributes the air evenly.

This geometry enables smooth acceleration of the air and reduces backflow and flow losses. The housing also ensures the required clearance for efficient airflow and contributes to the reduction of noise and energy losses.