Air handling units are a key component of modern ventilation and air conditioning systems. They ensure that buildings and rooms are supplied with treated air in a controlled manner. Depending on the application, the outside air is filtered, heated, cooled, humidified, or dehumidified before it enters the building as supply air.

The abbreviation AHU stands for “air handling unit”. An AHU, however, is not to be equated with the entire HVAC system. According to DIN EN 13053, the RLT unit is a component of an indoor air technology system. The overall system also includes, for example, air ducts, air outlets, and other components within the building.

What is the function of an AHU?

The basic function of an AHU unit is to treat and distribute air in accordance with the requirements of a building or process.

In the simplest case, outdoor air is drawn in, filtered, and introduced into the building as supply air. At the same time, stale exhaust air is removed from the rooms.

Modern air handling units, however, can do much more.

Depending on the application, they can heat or cool the air, add or remove moisture, and purify it through various filter stages. At the same time, At the same time, a large portion of the thermal energy contained in the exhaust air can be reused via a heat recovery system. Which functions are actually needed depends on the specific application.

Which functions are actually needed depends on the specific application.

An office building places different demands on AHU systems than a swimming pool, a hospital, a production facility, or a data center. For this reason, AHU can vary considerably in design, size, and technical features.

How does an air handling unit work?

A typical AHU operates with multiple air streams.

Outdoor air refers to the air drawn in from outside. Inside the AHU, it is treated according to requirements and then delivered as supply air into the rooms.

The air extracted from the rooms is referred to as exhaust air. After, for example, usable thermal energy has been transferred via the heat recovery system, it leaves the building as exhaust air.

In between are the various components of the air handling unit.

Filters remove particles from the air. Heat exchangers transfer heat or cold. Fans provide the necessary air movement. Dampers regulate airflows, and a corresponding sensor system measures temperatures, pressures, humidity levels, and other operating parameters.

The control system coordinates the interaction of these components.

An air-handling unit is therefore not a single ventilation component, but rather a system consisting of various functional areas that together produce the desired air quality and the required climatic conditions.

What components make up an air-handling unit?

The specific design depends on the task at hand. Typical components include, for example:

• Air filters
• Supply and exhaust fans
• Heating and cooling coils
• Heat recovery systems
• Dampers and actuators
• Silencers
• Sensors and probes
• Control and Regulation Technology
• Depending on the application: Humidification or dehumidification systems

In addition, other functions can be integrated directly into the AHU.

For custom-configured HANSA Blue Line units, for example, integrated mechanical refrigeration or heat pumps, cold and hot water coils, humidification and dehumidification, as well as various systems for air treatment are possible.

Which components are appropriate is therefore not determined solely by the size of the building. The specific air-conditioning task is the decisive factor.

Where are air handling units used?

Air handling units are used wherever natural ventilation is insufficient or where specific requirements for air quality, temperature, humidity, or process conditions must be met.

Typical applications include:

• Office and administrative buildings
• Schools and educational institutions
• Hospitals and medical facilities
• Industrial and manufacturing buildings
• Swimming pools
• Laboratories and cleanrooms
• Museums
• IT and server rooms

The requirements can vary greatly.

In schools, for example, air quality, acoustics, and energy-efficient air exchange are the top priorities. In swimming pools, high humidity levels must also be controlled, and special requirements for dehumidification and corrosion protection must be taken into account. Hygienically sensitive areas , high humidity loads must also be controlled, and special requirements for dehumidification and corrosion protection must be taken into account. Hygienically sensitive areas require special filter and equipment designs. In industrial applications , on the other hand, process conditions or particularly large air volumes can be decisive. In the case of data centers and server rooms, the focus is on the safe and energy-efficient removal of high heat loads. An overview of the various applications is provided in the section on

The Applications section of HANSA Klimasysteme provides an overview of the various applications.

That is why there is no single air handling unit that works for all applications.

Custom air handlig units from HANSA Klimasysteme

HANSA Klimasysteme develops and manufactures AHU's for various applications. A key focus is on project-specific configuration.

With the HANSA Blue Line, for example, the units are designed individually according to the respective task. The Factors taken into account include the required air volume, outdoor and indoor conditions, heat recovery, heating and cooling concepts, control systems, and installation conditions.

As a result, an air-handling unit can contain exactly the components required for the respective project.

This customized design is a key difference between a project-specific AHU and a ventilation product with fixed predefined functions.

For planning purposes, this means: The starting point is not the question of, which off-the-shelf unit to purchase, but rather what requirements the HVAC system must meet.

These requirements then determine the appropriate unit configuration.

Air handling units can vary greatly in design. While some units are used primarily for controlled air exchange, others also perform tasks such as heating, cooling, humidifying, and dehumidifying, or the precise control of specific indoor air conditions.

Their size, airflow capacity, and installation requirements also vary considerably. Which type of unit is suitable therefore depends not only on the size of a building, but above all on the specific ventilation and air-conditioning requirements.

Ventilation unit, air conditioning unit, or full-featured air conditioning unit?

Air-handling units can be distinguished primarily by the air-handling functions they perform.

A ventilation unit is primarily designed for controlled air exchange. Outside air is drawn in, filtered, and introduced into the building as supply air. At the same time, At the same time, stale exhaust air can be removed. A heat recovery system can make a large portion of the thermal energy contained in the exhaust air reusable.

An air conditioning unit performs additional air handling functions. These may include, for example, the targeted heating or cooling of the supply air.

With a full-featured air conditioning unit, in addition to temperature and air quality, other air conditions can also be specifically controlled. These include, in particular, humidifying and dehumidifying the air.

In practice, the distinctions between these terms are fluid. Therefore, what matters is not so much the name of a unit as the question of, which functions are actually required for the specific application.

Centralized and Decentralized Air Handling Units

Another distinction concerns the way in which a building is supplied with treated air.

In a central AHU, a single AHU serves larger areas or multiple rooms. The treated air is distributed throughout the building via a duct network, and the exhaust air is either recirculated or vented accordingly.

Centralized units are particularly suitable when large volumes of air need to be treated or when multiple air-handling functions are to be combined in a single system.

In a decentralized ventilation system, on the other hand, individual ventilation units are located directly in or near the rooms to be served. This allows the extent of the necessary ductwork to be reduced.

A typical application is, for example, schools. There, both centralized or floor-by-floor systems as well as decentralized classroom units can be used. HANSA offers various unit concepts for this purpose, ranging from centralized HVAC units to the Luftbox 800, a decentralized ventilation unit.

Which solution is more suitable depends, among other things, on the building size, room layout, airflow rates, acoustics, available space, and the structural feasibility of installing a duct network.

Individual AHU's and compact units

HVAC units also differ in the extent to which they can be adapted to a specific project.

Custom-configured HVAC units are assembled according to the specific climate control requirements. Airflow capacity, dimensions, heat recovery, filtration, heating and cooling concepts, control systems, and other features can be tailored to the project’s requirements.

This principle is applied, for example, in the HANSA Blue Line series. The units have a modular design and can be equipped with, among other things, various heat recovery systems, integrated refrigeration technology or a heat pump, cold and hot water coils, as well as humidification and dehumidification systems.

Compact units take a different approach. Here, frequently used functions are combined into a space-saving and largely standardized unit design. This simplifies planning, manufacturing, and installation without having to sacrifice important functions of an HVAC system.

The HANSA Kompakt Line, for example, includes compact ventilation and air-conditioning units for various applications in sports and event venues, educational institutions, public buildings, and smaller production and commercial areas.

Whether a custom-configured AHU or a compact unit is more appropriate, therefore depends on the specific application. For complex requirements, a custom configuration offers more options, while for clearly defined standard applications, a compact unit can be a cost-effective solution.

Indoor installation, outdoor installation, or rooftop unit

The installation location also influences the design of an air-handling unit.

In the case of indoor installation, for example, the unit is located in a mechanical room inside the building. Among other things, the following must be taken into account: the existing room dimensions, transport routes, maintenance areas, and the connection to the ductwork system.

If there is insufficient space inside the building or if other planning considerations warrant it, air handling units can also be designed for outdoor installation.

Another option is installation as a rooftop unit. In this case, the air handling unit or mechanical room is located on the building’s roof.

Outdoor and rooftop installations entail additional requirements. The housing, insulation, sealing, and other components must be designed so that the unit is reliably protected against the elements.

Individually configured HANSA Blue Line units can be designed for both indoor and outdoor installation, as well as for use as a rooftop unit.

Specialized Units for Specific Applications

In addition to standard ventilation and air conditioning units, there are HVAC units that are developed or configured for very specialized applications.

In swimming pools, for example, large moisture loads must be managed. At the same time, the high humidity and chloride-containing atmosphere place special demands on dehumidification, heat recovery, and corrosion protection. In

In, on the other hand, hygiene-sensitive areas, the focus is on air purity, filtration, hygienic design, and a secure separation of different zones.

Laboratories and cleanrooms may have particularly precise requirements for temperature, humidity, air purity, and pressure conditions.

For data centers, server rooms, and technical rooms, on the other hand, the focus is on the reliable and energy-efficient removal of high heat loads. In some cases, equipment designs developed specifically for heat dissipation are used here. The type of an HVAC unit is therefore always determined by its intended purpose. A unit for an office building does not need to have the same functions as a unit for a swimming pool, a cleanroom, or a computer room.

The type of AHU is therefore always determined by its intended application. A unit for an office building does not need to have the same functions as a unit for a swimming pool, a cleanroom, or a data center.

Which air handling unit is the right one?

Selecting a suitable AHU does not begin with a specific unit series, but rather with the requirements of the building or process.

Important criteria include, for example:

• required air flow rate
• Type and extent of air treatment
• Heating and cooling requirements
• Temperature and humidity requirements
• Heat recovery and energy efficiency
• Hygiene and filtration requirements
• Acoustics
• Available installation space
• Indoor or outdoor installation
• Control and Integration into the Building Management System

Only once these requirements are known can a decision be made as to whether, for example, a compact, decentralized, or custom-configured HVAC unit is the right solution.

HANSA Klimasysteme therefore offers a variety of unit concepts. The range extends from decentralized and compact ventilation units to custom-configured ventilation and full-air-handling units, all the way to specialized solutions for specific applications. The HANSA Klimasysteme product and solution portfolio provides an overview.

The key is not to pack as many functions as possible into a single unit, but rather to provide exactly the functions that are actually needed for a reliable and energy-efficient operation.

An air handling unit consists of various components that work together to ensure that air is moved, filtered, and conditioned according to the requirements of a building or process.

Which components are actually needed depends on the specific air-handling task. While a simple ventilation unit, for example, primarily ensures controlled air exchange, extensively equipped air handling units can also heat, cool, humidify, or dehumidify, and precisely control various air conditions.

The design of an air handling unit is therefore typically modular. The individual functional areas are combined in such a way that air volume, air quality, temperature, humidity, and energy efficiency meet the requirements of the respective application.

Filters – Air Quality and Component Protection

Air filters are among the fundamental components of an air handling unit. They remove particles from the intake air and thus contribute to the desired air quality within the building.

At the same time, filters also protect the downstream components of the air handling unit. Otherwise, dust and other contaminants could, for example, accumulate on heat exchangers, fans, or other components and impair their function.

The type of filters used depends on the outdoor air quality and the requirements of the specific application. In hygienically sensitive applications, for example, higher or multiple filter stages may be required.

However, filters also affect the system’s energy consumption. As air flows through the filter media, a pressure drop occurs that the fan must overcome. As the filter becomes increasingly contaminated, this pressure drop can increase.

Filtration, air quality, maintenance, and energy efficiency must therefore be considered together.

Fans—the Drive Behind Airflow

Without a fan, there is no controlled airflow. The fans in an air-handling unit ensure that the required air volume is transported through the unit and the connected ductwork system.

In doing so, various resistances must be overcome. Pressure losses occur, for example, at filters, heat exchangers, dampers, and silencers, as well as in the connected duct network.

Therefore, two parameters in particular are crucial for the selection and sizing of a fan: the

• the required air flow rate
• the required pressure increase

Modern fans can have their speed controlled. This allows the air volume delivered to be adjusted to the actual needs of the system. Since fans in many AHUs are operated over long periods of time,

Since fans in many AHUs operate over long periods of time, both their efficiency and their speed control have a significant impact on the system’s electrical energy consumption.

Heat Recovery – Utilizing Energy from Exhaust Air

In AHUs with supply and exhaust air, the air exhausted from the building often still contains usable thermal energy. A heat recovery system can transfer part of this energy to the outdoor air.

In winter, this allows the cold outdoor air to be preheated before additional heating energy must be used. Depending on the system and operating conditions, energy recovery can also help reduce cooling demand in the summer.

Various systems are available for heat recovery. Common solutions include:

• Plate heat exchangers
• Rotary heat exchangers
• Combined-cycle systems

Which system is suitable depends, among other things, on air volumes, space constraints, requirements for separating the air streams, and the respective operating conditions.

HANSA uses a variety of methods in its air-handling units. In the Blue Line, for example, plate and counterflow heat exchangers, rotors, or combined circulation systems can be used.

Heating and cooling coils – achieving the desired supply air temperature

Heat recovery can provide a significant portion of the required thermal energy. However, it is often insufficient to achieve the desired supply air temperature under all operating conditions.

For this reason, air handling units can be equipped with heating and cooling coils.

A heating coil transfers heat to the air flowing through it. A cooling coil, on the other hand, removes heat from the air, thereby lowering its temperature.

The necessary heat or cooling can be provided by an external supply system. Possible options include hot and cold water coils, which are connected to the corresponding building services.

Alternatively, the refrigeration system can also be integrated directly into the air handling unit, depending on the unit’s design.

Refrigeration Technology and Heat Pumps – Generating Cooling Directly in the air handling unit

If a mechanical refrigeration system is integrated directly into the air handling unit, the cooling required for air cooling can be generated directly within the unit.

In this setup, the ventilation unit, refrigeration system, and control system operate as a single integrated system. This enables the individual components to operate in a coordinated manner.

Depending on the system design, a reversible refrigeration system can also be operated as aheat pump. This allows the same system to be used for both cooling and heating.

HANSA develops and integrates refrigeration systems and heat pump systems for its ventilation and air conditioning units. In custom-configured Blue Line or Pool Line units, mechanical refrigeration or heat pumps can be directly integrated into the air handling unit.

Humidification and Dehumidification – Controlling Air Humidity

In certain applications, it is not enough to simply control the air temperature; the humidity must also be maintained within defined ranges.

If the air is too dry, humidification may be necessary. Conversely, in cases of high humidity loads, moisture must be specifically removed from the air.

This is particularly evident in swimming pools. The evaporation of pool water continuously generates high moisture loads there, which must be controlled by ventilation and dehumidification technology.

But industrial processes, museums, laboratories, and other sensitive areas as well can impose precise requirements on relative humidity.

Which humidification or dehumidification technology is used therefore depends on the application and the required indoor air conditions.

Dampers, silencers, and other components

In addition to the major functional areas, an air handling unit contains numerous other components that are necessary for reliable operation.

Dampers open, close, or regulate air pathways. They can, for example, be used to block certain airflows, redirect them, or enable different operating modes.

Silencers reduce the transmission of noise through the air duct system. This is particularly important in applications with high acoustic requirements, such as offices, schools, or event venues. Depending on the unit design, additional components such as condensate pans, droplet separators,

Depending on the system design, additional components such as condensate pans, droplet separators, inspection access panels, measurement points, and other parts may also be included.

The components required are determined by the specific air-handling task and the requirements for operation, maintenance, hygiene, and acoustics.

Sensors and Control—The Interplay of Components

To ensure that the individual components of an air handling unit work together effectively, the system’s current operating status must be monitored.

Sensors and probes are used for this purpose. They can, for example, measure the following parameters:

• Temperatures
• Humidity
• Pressures and pressure differentials
• Air flow rates
• CO₂ concentrations
• Other application-specific parameters

The measured values are processed by the measurement, control, and regulation technology. Based on this, for example, fan speeds can be adjusted, dampers can be positioned, and heating, cooling, or dehumidification capacity can be regulated. This allows the air handling unit to respond to changing conditions in the building and to different operating states.

As a result, the air handling unit responds to changing conditions in the building and to different operating states.

Control is therefore not an additional function independent of the actual air-handling unit. It connects the individual components into a functioning overall system.

The Housing—More Than Just an Outer Shell

All components of the air handling unit are located within or on a common housing structure.

The housing of an air-handling unit must meet various requirements. These include, among other things, mechanical stability, airtightness, thermal insulation, and the minimization of thermal bridges.

At the same time, the unit must be designed so that key components remain accessible for inspection, cleaning, and maintenance.

For outdoor installation, additional requirements regarding protection against weather conditions apply. In corrosive or hygienically sensitive environments, special materials and surfaces may also be required.

The housing is therefore an essential component of the technical and energy efficiency of an air-handling unit.

How are the components of an air-handling unit assembled?

Not every air-handling unit requires all available components. The decisive factor is, what task the system is intended to perform.

For a custom-configured air handling unit, the project’s requirements are therefore first considered. These include, for example:

• required air volume and pressure increase
• required air quality and filtration
• heating and cooling requirements
• temperature and humidity requirements
• Type of heat recovery
• Hygiene and acoustic requirements
• Control and automation concept
• Space Availability and Installation Conditions

Based on these factors, the necessary components are selected and coordinated with one another.

With the HANSA Blue Line and HANSA Pool Line, ventilation and full-featured air-handling units are configured specifically for each project. Heat recovery, fans, filters, heating and cooling technology, humidification and dehumidification, as well as MSR and DDC control, can be combined according to the specific air-handling task.

Therefore, the quality of an air-handling unit is not determined by a single component. It is the coordinated interaction of airflow, filtration, fans, heat recovery, thermal air treatment, sensors, and control systems that transforms the individual components into a fully functional AHU.

The design of an air handling unit begins with the requirements of the building or process. How much air is needed? What temperatures and humidity levels need to be achieved? Does the air need only to be filtered and heated, or does it also need to be cooled, humidified, or dehumidified?

Step by step, these requirements give rise to the technical unit design. In this process, air flow rate, pressure drops, thermal capacity, heat recovery, filtration, acoustics, control, and the available space must all be coordinated.

An air handling unit is therefore not selected based solely on its air flow rate. The key factor is the interaction of all components under the specific operating conditions.

What air volume is required?

One of the most important parameters in the design process is the airflow rate. It describes the volume of air that must be moved through the air handling unit within a specific time period and is typically expressed in cubic meters per hour (m³/h).

The required air flow rate depends on the specific application. For example, a school has different requirements for air exchange than a production facility, a laboratory, or a swimming pool. Depending on the application, the following factors, among others, may play a role:

Depending on the application, the following factors, among others, may play a role:

• Number of people and room occupancy
• Size and use of the rooms
• Pollutant or odor levels
• Moisture loads
• thermal loads
• Process or production requirements
• Hygiene requirements

The required air flow rate is a key factor in the sizing of the air handling unit and many of its components.

Why is pressure drop important?

The fan must not only deliver the required air volume; it must also simultaneously overcome the resistance within the air-handling unit and the connected air duct system.

Pressure drops are caused, for example, by:

• Filters
• Heat exchangers
• Dampers
• Silencers
• Air ducts
• Elbows and Fittings
• Air Diffusers

The required airflow rate and the pressure difference to be overcome determine a significant portion of the fan design.

Energy efficiency also plays an important role here. An unnecessarily high pressure drop causes the fans to consume more electrical power.

An energy-efficient AHU therefore considers not only individual components, but the entire airflow path.

What temperatures must be achieved?

In addition to the air volume, the thermal requirements must be taken into account during the design process.

This involves assessing the outdoor air conditions under which the system will be operated and the supply air and room air conditions that are to be achieved.

In winter, for example, cold outdoor air must be heated. In summer, on the other hand, cooling may be necessary.

Heat recovery can handle a portion of this task. Heat recovery utilizes thermal energy from the exhaust air to reduce the additional heating or cooling demand.

The remaining heating or cooling capacity required must be provided by appropriate components. These may include hot and cold water coils or a refrigeration system or heat pump that is directly integrated into the unit. These may include a refrigeration system or heat pump. gehören.

When must humidity be taken into account?

For many applications, it is sufficient to control air volume and temperature. In other areas, humidity is an additional important design parameter.

This is particularly evident in swimming pools. Evaporation of the pool water continuously generates high moisture loads. The AHU must therefore be designed so that the moisture can be reliably removed from the swimming hall or extracted using suitable systems.

Museums, laboratories, production areas, and other sensitive applications may also have specific requirements for relative humidity.

If specific humidity levels must be maintained, this affects, among other things, the design of the cooling, humidification, and dehumidification systems.

Which heat recovery system is suitable?

Heat recovery is an important component of many modern air handling units. However, which system is used depends on the requirements of the specific project.

Possible systems include, for example:

• Plate and counterflow heat exchangers
• Rotary heat exchangers
• Circulating composite systems

In addition to energy efficiency, spatial constraints and the requirements for separating supply and exhaust air also play a role in the selection process.

A combined circulation system, for example, may be a good option if supply and exhaust air areas must be physically separated from one another. Other systems, on the other hand, allow for a more compact unit design.

Heat recovery is therefore taken into account right from the initial design phase of the unit and not simply added as an afterthought.

What filters are required?

Air quality requirements must also be taken into account during the design phase.

Which filtration is required depends both on the quality of the outdoor air and on the building’s use.

Different requirements apply in a normal occupied area than in a hygiene-sensitive area or in laboratories and cleanrooms.

When selecting filters, the resulting pressure drop must also be taken into account. This is because the higher the resistance in the air path, the more power the fan must generate. Filtration and fan sizing are therefore directly related.

Filtration and fan sizing are therefore directly related.

How do space and installation affect unit design?

A technically suitable air handling unit must also fit into the building or at the intended installation site.

Therefore, the following points, among others, must be taken into account as early as the planning stage: -

• available installation space
• permissible unit height and width
• Transport and access routes
• position of the air connections
• Required maintenance and inspection areas
• Indoor or outdoor installation
• Structural and load-bearing requirements

Especially in existing buildings, limited space can have a significant impact on the unit’s design.

For outdoor installation, additional requirements apply to the enclosure, insulation, and weather protection. The

The mechanical design of an air handling unit is therefore just as much a part of the design as its air-handling and climate control functions.

What role do sound and acoustics play?

Fans and airflow generate noise. When designing an air handling unit, the building’s acoustic requirements must therefore also be taken into account.

This is particularly relevant, for example, in offices, schools, conference rooms, event spaces, or other noise-sensitive areas.

Noise levels can be influenced, among other things, by the selection and operating point of the fans, airflow velocities, the unit’s design, and the use of silencers.

Acoustics should therefore not be considered only after the system has already been built, but should be an integral part of the equipment design.

Why is control part of the design?

An air handling unit rarely operates continuously under the same conditions. Outdoor temperature, room occupancy, heating and cooling loads, and the actual air demand change during operation.

The measurement, control, and regulation technology must therefore be tailored to the unit’s design and the specific application.

Sensors measure the relevant operating parameters. The control system can then, for example, adjust fan speeds, damper positions, heat recovery, and heating, cooling, or dehumidification capacity.

At the same time, the planning phase must define how the air handling unit is to be integrated into an existing building automation or building management system. Mechanical engineering, refrigeration and heating technology, sensor technology, and control systems should therefore be considered as a unified system as early as the design phase.

Mechanical, refrigeration, and heating systems, as well as sensor technology and control systems, should therefore be considered as a single integrated system already during the design phase.

From the Requirements to the Individual Air-Handling Unit

The design of an air-handling unit is thus a combination of numerous technical requirements.

In simple terms, the process of arriving at the appropriate unit concept can be broken down into several steps:

1. Determine the requirements of the building or process
2. Determine the required air flow rate
3. Define outdoor, supply, and room air conditions
4. Determine heat recovery as well as the heating and cooling concept
5. Take filter, hygiene, and acoustic requirements into account
6. Check the installation location, dimensions, and maintenance areas
7. Determine the control and automation concept
8. Select and coordinate components

For custom-configured HANSA Blue Line units, the air-handling unit is assembled based on these project-specific requirements. This allows, among other things, fans, filters, heat recovery, heating and cooling technology, integrated refrigeration or heat pumps, as well as measurement, control, and DDC technology.

The result is therefore not an air-handling unit with as many functions as possible, but rather a unit whose design and performance are tailored to the actual task at hand.

Careful design also lays the foundation for reliable, energy-efficient, and demand-driven operation of the entire air-handling system.