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Air Handling Units (AHU)

AHU's for Energy Efficient Ventilation

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Our centrifugal fans with free running impellers are designed for installation into appliances such as air handling units.

Air Handling Unit

An air handling unit is a factory-made case assembly consisting of a fan or fans and other necessary equipment to perform one or more of the functions of circulating, cleaning, heating, cooling, humidifying, dehumidifying and mixing of air. Small air handlers for local use, are called terminal units. The air handler us normally constructed around a framing system with metal infill panels as required to suit the configuration of the components.



The AHU is used to control the following parameters of the space. 

There are basically two types of air handling unit that are used; Draw-Through or Blow-Through.

In the Draw-Through type, the fan pulls the air through the mixing box, filters and cooling coil before discharging it from the fan outlet to the space to be conditioned or to the ducting network. The design can be vertical or horizontal. In this case, the section before the fan has negative pressure.

In the Blow-Through type, the fan blows the air through the mixing box, filters and cooling coil before discharging them to the space being conditioned or the ducting system. In this case, the section after the fan has positive pressure.

AHU Fan Selection

In air handling units, centrifugal fans are used to circulate the air to the various parts of the sections in the building. The selection of the fan will depend on the air volume and the static pressure required of the system. Usually, the designer of the system will use a specialised software to do this selection.

In order to reduce the effect of vibration on the panel, the motor and the fan are usually installed on the vibration isolator except when the drive assembly is external to the fan casing.

The use of variable air volume (VAV) systems is becoming more popular as the volume of the air being discharged can be varied depending on the load condition. If the load is high, the fan speed will be higher and if the load is lower, the speed of the fan will be lower.

The speed of the fan is varied using a frequency inverter instead of a conventional motor. A whole range of fan speed from super low to super high can now be utilised based on the load conditions required, therefore a frequency inverter can provide better control of the fan speed.

A greater focus on the development in EC technology has enabled better use of energy and is in line with the move to more energy efficient products (ERP).

Requirement of AHU Systems

The requirements on a ventilation system are not always the same. In many applications, all that is required is a straightforward exchange of air, whereas in other applications the requirements can vary according to the temperature, humidity and purity of the air. Noise is also a significant factor to consider when choosing AHU fan components.

Axair Fans can supply components for efficient air movement within air handling units including backward curved impellers, EC forward curved centrifugal fans and belt driven options where required.

Industrial Fans For AHU's

Backward Curved Centrifugal Impellers

Backward Curved Impeller For AHU'sOur high performance centrifugal impeller without spiral housing, the E-Series “REVOLUTION” is a range specifically designed for volume flow. Manufactured from aluminium, the E range is designed and manufactured especially for the use of larger volume flow and lower pressure coupled with superior noise reduction and quiet operation. The impellers are manufactured using a black, UV-stabilised, long glass-fibre reinforced polypropylene.




Material Benefits:

Weighing 1.22 kg/m³, the impellers are extremely lightweight when compared with aluminium or steel alternatives. Therefore, the mass of inertia and start-up resistance is minimal. With improved dirt resistance, In-balance during operation is effectively eliminated.

GKHM Backward Curved AHU's


When used with an Electronically Commutated Motor (EC-Motor) or an AC-External Rotor Motor, Axair centrifugal fans with reduced noise, free-running, backward curved, high performance impellers make a very compact, efficient and optimally designed fan unit.


The fan units are available as:

Combining highly automated impeller manufacturing, efficient sheet metal processing and Rosenberg developed EC-Motors or voltage controllable AC-External Rotor Motors enables us to manufacture fan modules which offer optimum performance for customers, while been optimally matched with the construction needs of the end application. The motor impeller of the E-Series “REVOLUTION“, will be gradually integrated into Rosenberg Standard-Ventilation Fans. The fan design complies to the machinery directive 2006/42/EG, EMC-Directive 2014/30/EU, low-voltage directive 2014/35/EU and ErP-Directive 2009/125/EG.

The ECFanGrid – Multiple Plug Fans Running in ParallelECFanGrid

An ECFanGrid consists of several modular backward curved centrifugal fans or plug fans arranged in a grid formation. This construction offers a number of advantages over conventional technology. It is equally suitable for new projects and as a replacement for large single fans in retrofit air handling units. Find out more.


Contact us on 01782 349 430 to discuss how we can assist with effective and efficient air movement within Air Handling Units.