In a ventilation system, conditioned indoor air is continuously discharged from the building as exhaust air. At the same time, outdoor air must be drawn in and brought to the required supply air conditions. Without heat recovery, a substantial proportion of the thermal energy already used would be lost.

Heat recovery uses part of this energy by transferring heat between the exhaust air and outdoor air. This can significantly reduce the additional heating or cooling demand of the air handling unit (AHU).

Various systems are available for AHUs. Common solutions include plate heat exchangers, rotary heat exchangers and run-around coil systems. Although they share the same fundamental objective, they differ considerably in their design, separation of air streams, space requirements and potential applications.

How does heat recovery work in an AHU?

The basic principle is particularly easy to explain in winter operation: the exhaust air leaving a building is generally warmer than the outdoor air being drawn in.

In the heat recovery system, some of this thermal energy is transferred from the exhaust air to the cold outdoor air. This preheats the outdoor air before it is heated further, if necessary, and supplied to the building.

As a result, the heating coil needs to overcome a smaller temperature difference, which can reduce the additional heating energy required.

The same principle can also be used for cooling. If the exhaust air is cooler than the warm outdoor air, thermal energy can be transferred in the opposite direction. This precools the outdoor air and reduces the load on the downstream refrigeration system.

Heat recovery is therefore not only relevant in winter. When correctly designed, it can improve the energy performance of an AHU in both heating and cooling operation.

What types of heat recovery systems are available?

Energy can be transferred between exhaust air and outdoor air in several ways. The following systems are particularly common in AHUs:

• Plate and counterflow heat exchangers
• Rotary heat exchangers
• Run-around coil systems (KVS)

These systems differ in more than just their construction. The physical arrangement of the supply and exhaust air paths, the required separation of the air streams, pressure losses, moisture transfer and the specific application requirements all play a role in selecting the right system.

There is therefore no single heat recovery system that is equally suitable for every AHU.

How does a plate heat exchanger work?

In a plate heat exchanger, outdoor air and exhaust air flow through separate channels. Thin heat transfer surfaces between the air streams allow thermal energy to pass from one stream to the other.

The plates keep the air streams separate while heat is transferred across the dividing surfaces.

Depending on the design, the air streams can be arranged in crossflow or counterflow configurations, for example. Combined or multistage designs, such as double plate heat exchangers, are also possible.

Plate heat exchangers have no moving parts involved in the actual heat transfer process. This makes the underlying mechanical principle relatively simple and robust.

Different designs are used in the HANSA Blue Line. The PT, DPT and GS variants use plate or counterflow heat exchangers and can be configured to meet project-specific airflow and performance requirements. DPT stands for double plate heat exchanger: two crossflow plate heat exchangers are arranged in series. This achieves high efficiency with parallel air routing.

How does a rotary heat exchanger work?

A rotary heat exchanger, often simply called a rotor, operates on a different principle.

A rotating thermal storage matrix alternately passes through the exhaust air and outdoor air streams. As warm exhaust air flows through it, the matrix absorbs thermal energy. Rotation then moves it into the outdoor air stream, where it releases some of that energy.

This process repeats continuously.

Depending on the material and coating, rotors can transfer moisture as well as heat. This can provide energy-related benefits for certain air conditioning applications.

Performance can be adjusted, among other things, by varying the rotor speed. This allows energy recovery to be adapted to different operating conditions.

Special rotors are available for intensive air dehumidification. This technology is used, for example, in battery manufacturing, where the supplied air must be extremely dry.

With a rotor, the air streams cannot be completely separated. Air transfer across the rotor always occurs from the higher-pressure side to the other air path.

Unlike a plate heat exchanger, the rotor is subject to mechanical stress, and its mechanically loaded components are subject to wear. These include the drive belt, motor, seals and rotor bearings. Control during start-up can also be challenging: unbalanced airflows and pressure conditions can cause the rotor to become misaligned and fail to start.

HANSA uses rotary heat exchangers, for example, in the Blue Line eco-R. The system is particularly suitable for applications with high airflow rates, provided that air quality requirements and the permissible transfer between air streams allow its use.

How does a run-around coil system work?

A run-around coil system (KVS) enables heat recovery without requiring supply and exhaust air to pass through the same location.

Each air stream contains its own heat exchanger. The heat exchangers are connected by a hydraulic circuit that uses a brine solution as the heat transfer fluid.

In heating operation, the heat transfer fluid absorbs energy from the warm exhaust air. This energy is transported through pipes to the heat exchanger in the outdoor air stream, where it is released.

This allows the outdoor air and exhaust air sections to be installed in physically separate locations.

A run-around coil system is therefore particularly useful when strict separation of the air streams is required or when the supply and exhaust air units cannot be installed next to each other for structural reasons. However, the coils required to achieve good heat transfer efficiency must be very large. As a result, their pressure loss is generally higher than that of rotary or plate heat exchangers, increasing the electricity consumption of the fans. The brine pump also consumes electricity. This system should therefore preferably be used where separation of the air streams is necessary.

In HANSA Blue Line KVS units, heat recovery is combined with the etaHydro hydraulic station. The pumping power of the brine circuit is controlled for energy-efficient operation, taking account of the recovered energy and airflow rates.

What are the main differences between plate heat exchangers, rotors and run-around coil systems?

All three systems transfer thermal energy between exhaust air and outdoor air. However, their technical operating principles differ significantly.

A plate heat exchanger transfers heat across fixed separating surfaces. The two air streams are kept separate within the heat exchanger.

A rotary heat exchanger, by contrast, contains a rotating thermal storage matrix that passes alternately through both air streams. Depending on the design, it can transfer moisture as well as heat.

In a run-around coil system, energy is transferred through an intermediate hydraulic circuit. This allows the air streams to remain completely separated in physical space.

These differences determine which system makes the most sense for a particular AHU.

What role does moisture recovery play?

Under certain conditions, energy recovery can transfer moisture as well as sensible heat.

Moisture transfer between air streams can be used deliberately with appropriately designed rotary heat exchangers, but also with certain plate heat exchangers, such as the Vapobloc from Polyblock.

Whether this is desirable depends on the application. In some buildings, moisture recovery in winter can help prevent the supply air from becoming excessively dry. In other applications, moisture or substance transfer between the air streams must be avoided as far as possible. There are also benefits in summer: humid outdoor air can be dehumidified in the heat recovery system. If further dehumidification is required in a downstream cooling coil through condensation, the cooling capacity needed for that process is reduced.

Requirements relating to air quality, humidity and separation of the air streams must therefore be considered when selecting the heat recovery system.

Can heat recovery also support cooling?

Heat recovery is often associated primarily with winter operation. However, the same basic principle can also be used in summer.

When outdoor air is warmer than exhaust air, some of the thermal energy can be transferred from the outdoor air to the cooler exhaust air. This means the outdoor air reaches the downstream components already precooled.

This can reduce the required capacity of the refrigeration system.

This principle can be taken further through indirect adiabatic cooling, for example. In the HANSA Blue Line ASB+, the exhaust air is cooled by humidification. A double plate heat exchanger then uses this additional cooling potential to cool the outdoor air without directly humidifying the supply air.

When assessing the energy performance of indirect evaporative cooling, it is important to consider more than just the cooling energy saved. The water consumption required must also be included in the overall assessment. Particularly where water availability is limited, energy savings, water demand and the specific climatic conditions at the installation site must be weighed against one another.

How is the right heat recovery system selected?

The most suitable system for an AHU cannot be determined solely by seeking the highest possible heat recovery efficiency.

Several requirements must be considered together when making a selection:

• Required airflow rate
• Temperature and humidity conditions
• Requirements for separating supply and exhaust air
• Permissible transfer of moisture or substances
• Pressure losses and auxiliary electrical energy consumption
• Available space and possible airflow arrangements
• Hygiene requirements
• Controllability under different operating conditions
• Maintenance and cleaning options
• Investment and operating costs

An energy-efficient system must therefore always be assessed in the context of the entire AHU. High thermal performance alone is not sufficient if it results, for example, in disproportionately high pressure losses or other disadvantages.

In individually configured HANSA Blue Line units, heat recovery can be designed to meet the requirements of each project. Available options include plate and counterflow heat exchangers, rotary heat exchangers and run-around coil systems.

A life-cycle assessment makes it possible to compare different unit concepts under realistic operating conditions and estimate their energy-related impacts over a longer period.

For this purpose, HANSA uses a calculation method developed by the German AHU Manufacturers' Association (Herstellerverband RLT-Geräte), which is integrated into the AIRCALC unit selection software. This allows the expected energy consumption of different system configurations to be estimated during the unit design stage.

This brings the selection of a heat recovery system back to its central principle: the decisive factor is not the highest individual performance figure, but the solution that is technically and energetically best suited to the overall system.

AHU units must condition outdoor air to meet a wide range of supply air conditions, depending on the season and application. In winter, heating is often required, while cooling may be necessary in summer. Modern refrigeration technology can handle both tasks.

If a refrigeration cycle is designed to be reversible, it can provide both cooling and heating. This allows the same system to be used for cooling in the summer and as a heat pump to provide heat in the winter.

There are various technical concepts for an air-handling unit in this regard. Cooling and heating can be generated externally and transferred via water-cooled coils. An external refrigeration system can also be connected to a direct evaporator in the air-handling unit. Another option is to fully integrate the cooling or heat pump technology directly into the AHU unit.

Which variant is suitable depends on the overall system design. Heating and cooling capacity, temperature levels, heat recovery, space requirements, controllability, energy consumption, and the existing technical infrastructure must all be considered together.

Why do air-handling units need heating and cooling?

The outdoor air drawn in varies greatly in temperature throughout the year. In order for it to be introduced into a building as supply air, its condition must be adjusted to meet the requirements of the building or process.

In winter, the outdoor air generally needs to be heated. A portion of the energy required for this can be recovered via the heat recovery system from the exhaust air. If this energy is insufficient, additional heat must be provided.

In summer, the situation can be reversed. High outdoor temperatures, solar radiation, people, and technical equipment can lead to a situation where cooling is required. The AHU unit must then extract thermal energy from the air.

Therefore, it makes sense not to view the provision of heat and cooling as two completely separate tasks. A reversible refrigeration cycle can perform both functions, depending on the design.

How can heating and cooling be provided for an air-handling unit?

Various system concepts are available for thermal air handling. A fundamental distinction must be made between the generation of heat or cooling and the transfer of this energy to the air.

Typical options include:

• external heat and cooling generation with water-cooled coils in the AHU unit
• external refrigeration system with a direct evaporator in the AHU unit
• refrigeration technology integrated directly into the air handling unit
• reversible cooling systems or heat pumps for heating and cooling operation

These options are not necessarily mutually exclusive. Depending on the project, different heating and cooling sources as well as various coils and operating modes can be combined.

How do heating and cooling coils work in the AHU unit?

Heating and cooling coils are heat exchangers through which thermal energy is transferred between a medium and the air stream.

In a heating coil, the medium flowing through it transfers heat to the air. In a cooling coil, on the other hand, heat is extracted from the air. As a medium, water or water-glycol mixtures, for example, can be used. The required capacity of a coil depends, among other things, on the

The required capacity of a coil depends, among other things, on the air flow rate, the inlet and outlet temperatures, the temperature level of the medium, and the heat transfer area.

At the same time, a coil causes a pressure drop on the air side. This pressure drop must be overcome by the fans, thereby affecting their electrical energy consumption. Coil size, capacity, and pressure drop must therefore be considered together.

How does an external cooling and heating supply work?

In an external supply system, heating and cooling are generated outside the AHU unit. Via a hydraulic circuit, hot or cold water—or suitable water-glycol mixtures—is delivered to the coils in the unit.

This concept is particularly suitable when a building already has a central heating or cooling supply, or when multiple consumers are to be supplied jointly.

In this case, the AHU does not require its own complete refrigeration system. Nevertheless, the coils, hydraulics, and control system must be precisely matched to the available temperatures and the required capacities.

Energy efficiency therefore depends not only on the AHU unit, but also on the efficiency of the external generation, the distribution, and the temperature levels actually available.

How does an external refrigeration system with a direct evaporator work?

An external refrigeration system does not necessarily have to be connected to the air-handling unit via a chilled water circuit. A direct evaporator within the air-handling unit is also possible.

In this configuration, the coil located in the airflow is a direct component of the refrigerant circuit. The refrigerant evaporates in the heat exchanger and, in doing so, absorbs heat from the air flowing through it.

Other components of the refrigeration system may be located outside the air handling unit. In this case, refrigerant lines run between the refrigeration system and the air handling unit instead of a chilled water circuit.

This makes it clear that the terms external refrigeration system and chilled water coil do not describe the same concept. An external refrigeration system can also be connected directly to a refrigerant coil built into the air handling unit. How does integrated refrigeration technology work in the air handling unit?

How does integrated refrigeration technology work in an air handling unit?

Another option is to integrate all components of the refrigeration cycle directly into the AHU unit. Air handling and refrigeration technology are then designed together as a single system.

The refrigeration cycle includes, among other things, a compressor, evaporator, condenser, expansion device, refrigerant, and the necessary safety and control technology.

One advantage of integration is that air handling, refrigeration, and control can be coordinated with one another as early as the unit design phase. A separate chilled water supply for the relevant air handling unit is then not required.

At the same time, the air-handling unit becomes more technically complex. The refrigeration cycle, accessibility, maintenance, safety, and control must therefore be taken into account already during the design phase.

For individually configured HANSA Blue Line units, the mechanical refrigeration system can be integrated into the air-handling unit in accordance with the requirements of the respective project.

How does a refrigeration system become a heat pump?

Refrigeration machines and heat pumps are based on the same thermodynamic principle. The refrigerant cycle absorbs heat at a lower temperature level and releases it at a higher temperature level.

If the system is designed accordingly, the refrigeration cycle can be operated reversibly. As a result, the same system technology can provide both cooling and heating for air handling.

In the summer, the refrigeration cycle can extract heat from the supply air, thereby cooling it. In the winter, the system can be operated as a heat pump and provide heat to warm the supply air.

This capability is particularly advantageous for AHU units because the thermal requirements vary throughout the year. While heat is required during the heating season, a system design may simultaneously be needed that can also handle increasing summer cooling loads.

A reversible refrigeration and heat pump system can handle both tasks with a single thermodynamic system. The prerequisite is that the refrigeration cycle, heat exchanger, and control system are designed from the outset for the intended operating conditions.

How do heat recovery and heat pumps work together?

Before generating additional heat or cooling, it is important to determine what energy is already available in the AHU system. Heat recovery plays a central role in this process. Heat recovery.

In winter, the warm exhaust air can first be used to preheat the cold outdoor air. The heat pump or another heat source then only needs to provide the remaining heating capacity. In summer, the energy flow can reverse. If the exhaust air is cooler than the outdoor air, heat recovery can help precool the outdoor air.

In summer, the energy flow can be reversed. If the exhaust air is cooler than the outside air, heat recovery can help pre-cool the outside air. The mechanical cooling system then only needs to handle the remaining cooling load. The mechanical cooling system then only needs to handle the remaining cooling load.

Heat recovery and refrigeration or heat pump technology should therefore not be designed and operated independently of one another. The key is the energy-efficient interaction of the systems.

Can refrigeration technology also be used for dehumidification?

In certain applications, refrigeration technology can be used not only to lower the temperature but also for dehumidification. To do this, humid air is cooled to the point where its temperature falls below the dew point.

Part of the water vapor contained in the air condenses on the cooling coil and can be drained off as condensate. This reduces the absolute humidity of the air.

This type of dehumidification places special demands on the system design. In addition to sensible heat, the latent heat released during condensation must also be removed. Furthermore, a suitable condensate pan and condensate drain are required.

However, dehumidification using refrigeration technology is only one of several possible methods and is not used in every application. In HANSA systems for swimming pools, for example, the refrigeration system is not used to dehumidify the pool air, but is designed as a heat pump to utilize the residual energy in the exhaust air after heat recovery. The specific requirements for swimming pool dehumidification are discussed in greater detail in the Swimming Pool Climate Wiki. Why are control and partial-load operation so important?

Why are control systems and part-load operation so important?

An AHU unit operates under maximum design conditions only for a portion of its operating time. Outdoor temperature, humidity, internal heat loads, and usage vary throughout the day and over the course of the entire year.

An efficient cooling and heating system must therefore be able to adjust its output to actual demand.

The measurement and control technology can, among other things, monitor temperatures, humidity levels, and other operating parameters, and coordinate heat recovery, heating and cooling capacity, fans, and other components.

Particularly in reversible systems, the control system must be able to handle different operating states. Depending on the requirements, it determines, for example, whether heat recovery is sufficient, whether additional heating or cooling capacity is needed, or whether the system must switch between different operating modes.

The efficiency of a system should therefore not be evaluated solely based on the maximum design point. Of great importance is the system’s performance under the actual partial loads that occur throughout the year.

What role does the refrigerant play?

The refrigerant transports thermal energy within the refrigeration cycle. Its properties influence, among other things, the possible temperature and pressure ranges as well as the design and operation of the refrigeration or heat pump system.

When selecting a refrigerant, in addition to its thermodynamic properties, one must also consider safety requirements, environmental impacts, and legal regulations. An important parameter in this context is the An important parameter in this context is the Global Warming Potential (GWP). It describes the greenhouse potential of a substance compared to CO₂.

An important legal basis is the EU F-Gas Regulation (EU) 2024/573. It gradually restricts the use of fluorinated greenhouse gases and sets out requirements and marketing bans for various refrigeration, air conditioning, and heat pump applications, as well as prohibitions on placing them on the market, depending on the application, capacity, and global warming potential of the refrigerant used.

As a result, the long-term availability and sustainability of a refrigerant become important factors as early as the planning stage of new systems. At the same time, potential alternatives must always be considered in the context of the technical and safety-related requirements of the respective system.

The choice of refrigerant is therefore an integral part of the overall system design and cannot be considered independently of the system’s capacity, application, temperature range, safety, and design.

Which system is suitable for providing cooling and heating?

There is no one-size-fits-all answer. A central supply system, an external refrigeration system with a direct evaporator, or an integrated reversible refrigeration and heat pump system can offer different advantages depending on the project.

The following points, among others, should be considered when making a selection:

• required heating and cooling capacity
• Temperature requirements during summer and winter operation
• Existing or planned central heating and cooling supply
• Possibility of using a reversible cooling and heat pump system
• Full-load and part-load performance throughout the year
• Options for heat recovery and further heat utilization
• Required temperature levels
• Space constraints and installation location of the AHU unit
• Ductwork and existing infrastructure
• Control capabilities and building automation
• Maintenance and accessibility
• Capital, operating, and energy costs

With custom-configured HANSA Blue Line units, various concepts for cooling and heating can be implemented in accordance with project requirements and coordinated with the rest of the air-handling system.

Why should cooling and heating provision be considered on a year-round basis?

When designing an air-handling unit, it is not sufficient to consider only the maximum heating demand in winter or the maximum cooling demand in summer. What matters most is how the entire system operates under the varying operating conditions throughout the year.

A reversible system can offer a particular advantage here: The invested system technology is not used exclusively for a seasonal operating scenario, but can be utilized for both heating and cooling.

For the energy assessment, however, all relevant energy consumption must be taken into account. In addition to the generated heat and cooling, this includes, for example, the electricity consumption of compressors, fans, and pumps.

Equally important is the interaction with heat recovery. The more existing thermal energy that can be utilized effectively, the lower the additional heating or cooling capacity required can be.

The design process should therefore not begin with the question of which chiller is needed. First, it must be determined, how much heating and cooling the AHU system must actually provide throughout the entire year, and how this can be generated, recovered, and utilized as efficiently as possible.

A modern air handling unit (AHU) must coordinate a wide range of components and operating conditions. Fans, dampers, heat recovery, heating and cooling capacity, and other functions must work together according to outdoor conditions, building use and actual demand.

Control technology performs this task. Sensors record the current system conditions, a DDC processes the measured values, and the control system adjusts the AHU components through the appropriate actuators.

Modern control concepts go beyond individual conventional control loops. AHUs can communicate with building automation systems, provide operating and energy data, and be monitored remotely. Model-based and model predictive methods also enable proactive optimisation of system operation.

What functions does an AHU control system perform?

The control system ensures that the required air conditions and operating parameters are maintained. It compares measured actual values with specified setpoints and adjusts suitable control variables when deviations occur.

If the supply air temperature is too low, for example, the control system can first check how much heat is available from heat recovery and then request additional heating capacity if necessary.

Possible AHU control functions include:

• Controlling temperature and humidity
• Controlling airflow rates and pressure conditions
• Demand-based fan operation
• Controlling and coordinating heat recovery
• Controlling heating and cooling capacity
• Coordinating integrated refrigeration and heat pump technology
• Monitoring filters and other unit components
• Implementing operating schedules and different operating modes
• Protective and safety functions
• Recording and transmitting operating and fault messages

What matters is not simply controlling individual components. A good control strategy considers their interactions and coordinates them as a complete system.

Which measured variables does the control system need?

Reliable information about the current system conditions forms the basis of demand-based control. The sensors required therefore depend on the application and the intended functions of the AHU.

Typical measured variables include:

• Outdoor, supply, extract and room air temperatures
• Relative or absolute humidity
• Pressure and differential pressure
• Airflow rate
• CO₂ concentration
• Other measurements used to assess air quality
• Temperatures and pressures within technical systems
• Electrical or thermal power and energy consumption values, where appropriate metering is installed

The same measurement can serve different purposes. Differential pressure measurement can be used to monitor a filter, for example, while pressure or airflow measurements can provide the basis for demand-based fan control.

Sensors should therefore not be regarded merely as an addition to the control system. Their selection, measuring range and positioning largely determine what information is available to the control system.

How does the DDC of an AHU work?

DDC stands for Direct Digital Control and refers to the digital control and regulation level of the system. Sensor measurements are collected here and processed according to programmed control strategies.

From these values, the DDC can derive setpoints for fans, damper actuators, control valves, pumps, heat recovery, and refrigeration and heat pump technology.

It also performs higher-level functions. These may include operating modes, time schedules, limit monitoring, fault messages, protective functions and communication with other automation systems.

The DDC thus forms the fundamental automation level of the AHU. Even when operating data is transferred to higher-level systems or advanced optimisation methods are used, the unit's basic control and protective functions remain essential at this level.

How are airflow, temperature and humidity controlled according to demand?

The requirements placed on an AHU change during operation. Outdoor temperature, humidity, occupancy, internal heat loads and building use can vary considerably throughout the day and year.

Demand-based control adapts system operation to these changes. If less air is needed, for example, fan speed can be reduced. Depending on the application, this may be based on pressure, airflow, CO₂ or other demand-related measurements.

Components should not operate independently when controlling temperature either. Available heat recovery can be used first, for example. If it is insufficient, additional heating or cooling capacity is provided.

With reversible refrigeration and heat pump technology, the control system must also coordinate different operating conditions and determine when heating or cooling is required.

If specific humidity requirements apply, humidification or dehumidification functions can also be incorporated into the control strategy. Temperature and humidity must be considered together because these two air properties are interrelated.

Why is coordination between components so important?

The energy efficiency of an AHU depends not only on the efficiency of its individual components, but also on when they operate and at what capacity.

A control strategy should therefore prevent different functions from unnecessarily working against each other. Simultaneous heating and cooling is a typical example of an operating condition that should be avoided unless there is a technical reason for it.

The same applies to unnecessarily high airflow rates or additional heating or cooling when existing energy-saving potential has not yet been fully utilised.

A coordinated control system therefore manages heat recovery, fans, air dampers, heating and cooling coils, and refrigeration and heat pump technology, among other components.

The control strategy thus has a significant influence on the AHU's actual energy demand during operation.

How is an AHU connected to building automation?

An AHU often operates as part of a higher-level building automation system. Suitable interfaces allow setpoints, operating states, measurements, warnings and fault messages to be exchanged between the AHU and the building management system.

The planning stage should therefore establish which information will be exchanged and which functions will be performed at each automation level.

The AHU's basic control, protective and safety functions can continue to be performed by its own DDC. The building management system can, for example, provide higher-level specifications, visualisation and coordination with other building systems.

In addition to conventional building automation, remote access to the AHU can be provided. With etaConnect, HANSA etaTECH offers a solution for securely connecting HANSA AHUs with integrated controls. This enables remote access and the transmission of fault and maintenance notifications, among other functions.

The options for remote monitoring and remote service are discussed in more detail in the etaTECH Wiki.

How can operating data be used for optimisation?

The control system generates extensive data during operation. Temperatures, pressures, humidity readings, setpoints and actual values, control outputs, operating states and running times describe how the AHU actually operates.

When this information is stored, visualised and analysed over an extended period, it can reveal insights that would not be immediately apparent from examining only the current system state.

For example, recurring operating conditions, deviations, unusual trends and potential opportunities for optimisation can be identified.

At HANSA etaTECH, etaVisu and etaWatch perform different tasks. etaVisu is used to visualise and analyse operating data. etaWatch extends this with energy monitoring and the recording of relevant consumption and efficiency data.

This provides an important basis for assessing not only whether an AHU is functioning, but also how it operates under real conditions and how much energy it uses.

Monitoring, visualisation and energy monitoring are covered in greater detail as separate topics in the etaTECH Wiki.

What are model-based and model predictive control?

Conventional control loops react to measured deviations between setpoints and actual values. Modern control approaches can additionally incorporate a model of system behaviour into the control strategy.

In model-based control, a model describes relevant relationships within the AHU system. This makes it possible to account for interactions between operating states, control variables, air conditions and energy use when making control decisions.

A more advanced approach is model predictive control (MPC). Here, the model is used to predict possible future system states. The control system can then select control variables to achieve specified objectives as effectively as possible over a defined future time horizon.

This approach differs fundamentally from purely reactive control: rather than responding only after a deviation has occurred, the control system can take the expected development of the system into account when making decisions.

This is particularly interesting for AHU systems because many influencing factors and components interact, while system behaviour is also affected by changing external conditions.

What role do AI and learning models play in AHU control?

A model for modern control does not have to consist solely of predefined mathematical relationships. System behaviour can also be described using data-driven or learning-based models.

Importantly, model-based control is not automatically the same as artificial intelligence. Physical models, data-driven models and AI methods are different approaches that can also be combined, depending on the system.

With etaSmart, HANSA pursues such a combined approach, linking neural networks with physics-based models and model predictive control.

The aim is not merely to consider the current state of the AHU system, but to model its behaviour and include future operating conditions in the optimisation process.

Conventional DDC control remains an important level of system automation. Advanced model-based methods build on existing system functions and operating information rather than replacing the AHU's basic protective and control functions.

The operating principles, applications and retrofitting options for such methods are discussed in more detail in the etaTECH Wiki article “AI in Ventilation Technology – Intelligent Control of AHU Systems”.

What is important when planning a modern AHU control system?

The control system should not be added only at the end of the unit design process. It must be developed alongside the mechanical and thermodynamic components and the requirements of the building or application.

Among other things, the following questions need to be answered:

• Which air conditions and setpoints must be maintained?
• Which measurements and sensors are required?
• Which components and functions need to be controlled?
• Which operating modes are required?
• How should the unit behave under different load conditions?
• Which protective and safety functions are needed?
• Which operating and energy data should be recorded?
• What visualisation, monitoring and remote access options are planned?
• Which interfaces to building automation are required?
• Should model-based or advanced optimisation methods be used?

At HANSA, project-specific configuration of electrical engineering, instrumentation and control technology is not limited to a single product series. With the exception of LF-Hy and Luftbox 800, the other AHUs can be individually adapted to the instrumentation and control requirements of each project.

This allows sensors, DDC, actuators, control strategies, interfaces and higher-level functions to be considered together with the unit design itself. Depending on the project, solutions for remote access, visualisation, energy monitoring or advanced model-based control approaches can also be included.

The decisive factor is therefore not simply that the AHU achieves a specified setpoint. A modern control system should consider the overall interaction between air handling, energy use, operating conditions and building requirements.

Proper filtration in an air-handling unit does not begin with the question of a specific filter class. First, it must be determined what function the filtration is intended to serve in the respective application.

In schools and office buildings, for example, good supply air quality is a top priority for the people in the building. In industrial settings, however, production processes or sensitive machinery may impose additional requirements. In laboratories, cleanrooms, and hospitals, on the other hand, there may be very stringent requirements for particle purity and hygiene.

It is not only the outdoor and supply air that must be considered. The exhaust air, too, is filtered to protect components of the HVAC unit from contamination. In recirculation mode or in cases where air may be transferred between the exhaust air and supply air sides, exhaust air filtration can also be relevant to the quality of the supply air.

That is why, at HANSA, filtration is designed as an integral part of the entire air-handling unit and tailored to the specific application.

How is the required filtration for an air-handling unit determined?

For air filters used in general ventilation systems, classification is based on ISO 16890. Filters are categorized, among other things, according to their separation efficiency for the particle fractions ePM1, ePM2.5, and ePM10. For coarser particles, there is also the ISO Coarse group.

However, the filter class alone does not determine a suitable filtration concept. The following factors, among others, must be taken into account during design:

• the quality and pollution level of the outdoor air
• Required quality of the supply air
• Use of the building
• Requirements of people, products, or processes
• Hygiene requirements
• Exhaust air contamination
• Type of heat recovery
• Possible air transfer between exhaust and supply air
• Recirculation or mixed-air operation
• Number and arrangement of filter stages

In general indoor air handling systems, filters in the ePM1 range are frequently used on the supply air side. Depending on the outdoor air quality and the desired supply air quality, filters ranging from, for example, Depending on outdoor air quality and the desired supply air quality, filters ranging from, for example, ISO ePM1 50% to ISO ePM1 80% or higher may be part of the filter design.

However, these ranges are not blanket specifications for certain types of buildings. The actual filtration required must be determined for the specific project.

Why is the exhaust air from an HVAC unit also filtered?

In a unit that handles both supply and exhaust air, the filtration of both air paths must be considered. While the filtration of the outdoor or supply air is largely determined by the desired supply air quality, the exhaust air filter primarily serves another important purpose: It protects the downstream components of the HVAC unit from contamination.

This applies in particular to components of the heat recovery system. Without proper exhaust air filtration, particles from the room air can deposit on heat exchangers and other components. This can impair the heat transfer, increase pressure losses, and raise the cleaning- and maintenance costs.

As a guideline, for exhaust air before heat recovery, filtration in the range of, for example, ISO ePM2.5 ≥ 50% is recommended. For exhaust air with higher particle loads, other or additional requirements may apply.

However, exhaust air filtration can also serve a second purpose. If, due to the design of the HVAC unit, there is a possibility of air transfer between the exhaust air and supply air sides, it must be taken into account that a portion of the exhaust air could affect the quality of the supply air.

In such cases, it may be advisable or necessary to design the exhaust air filtration system with a higher separation efficiency and, if necessary, to a level matching that of the supply air filtration.

This becomes particularly evident in recirculation and mixed-air modes. If exhaust air is specifically recirculated into the supply air, the filtration system must be designed accordingly. For such applications, for example, filtration with a minimum efficiency of ISO ePM1 ≥ 50% is required.

Outdoor air, supply air, and exhaust air filtration should therefore not be considered separately from one another. Together with air distribution and heat recovery, they form the filtration concept of the HVAC unit.

What type of filtration is appropriate for schools?

In the case of school ventilation, the priority is good indoor air quality for many people present at the same time. The requirements for filtration are also strongly influenced by the building’s location.

A school in an area with low outdoor air pollution may require a different filtration concept than a school located directly next to a heavy-traffic road. In addition to coarser particles and pollen, therefore, particulate matter pollution in the outdoor air must be taken into account in particular.

For the supply air, filtration in the ePM1 range may be advisable or even necessary. Depending on outdoor air quality and the desired supply air quality, filters in the range of, for example, ISO ePM1 50% to ISO ePM1 80% or higher can be used.

Whether one or more filter stages are appropriate is determined based on the actual outdoor air conditions and the desired indoor air quality. This is determined.

What is the role of filtration in office buildings?

Even in the case of office ventilation, the quality of the breathing air is the primary focus. Particularly in urban areas, particulate matter and other pollutants in the outdoor air can be relevant to filter selection.

Depending on outdoor air quality and the desired supply air quality, filtration in the ePM1 range can therefore also be used in office buildings. Typical designs can range, for example, from ISO ePM1 50% to ISO ePM1 80% or higher. Typical designs can range, for example, from ISO ePM1 50% to ISO ePM1 80% or higher.

However, the building designation “office” alone is not the decisive factor. Location, outdoor air pollution, building use, and desired indoor air quality collectively determine the filtration concept.

Why can filtration in industry and manufacturing look completely different?

In the case of HVAC units for industry and manufacturing, an additional task may be required beyond the protection of people: the protection of production processes, machinery, or products.

The requirements range from ventilating a standard production hall to air treatment for sensitive manufacturing processes. Depending on the application, the removal of coarser particles may be sufficient, or a high level of fine dust removal in the ePM1 range may be required.

For certain production processes, multi-stage filtration concepts or special filtration methods may also be necessary. The decisive factor here is which contaminants are critical for the respective process.

In industrial applications, special attention must also be paid to the exhaust air side. Production processes can contaminate the exhaust air with particles or other substances. Exhaust air filtration must then be tailored to protect the components of the HVAC unit as well as to the respective air distribution and heat recovery design.

A production process can thus place significantly higher or simply different filtration requirements on the system than those of the people in the same building.

What type of filtration is required in laboratories and cleanrooms?

In the case of laboratories and cleanrooms, the requirements for particle purity may be significantly higher than in a conventional comfort ventilation system.

In such cases, relying on a single filter compliant with ISO 16890 may, under certain circumstances, not be sufficient. The filtration system may consist of several stages that are coordinated with one another.

Filters used in general indoor air conditioning systems, for example, initially handle pre-filtration and fine dust filtration. Depending on the required purity, EPA or HEPA air filters may then be used. Such air filters are not classified according to the ePM groups of the

Such particulate filters are not classified according to the ePM groups of the ISO 16890 standard, but rather according to the standards and test procedures specifically designed for this purpose.

At the same time, in laboratory applications, the exhaust air may require special attention. Depending on the process, substances or particles from the room cannot simply be vented through the exhaust air and the HVAC unit. In such cases, special exhaust air filters or additional air treatment measures may be required.

Supply and exhaust air filtration must therefore be planned in conjunction with the room class, airflow, pressure maintenance, and the requirements of the respective laboratory or production process.

What type of filtration is required in hospitals and hygienic areas?

In hospitals and hygiene-sensitive areas, filtration plays a particularly important role. In addition to ensuring a high level of indoor air quality, the protection of patients, staff, medical processes, and medical devices can be critical here.

Requirements within a hospital vary significantly. Patient rooms, examination rooms, intensive care units, isolation areas, airlocks, and operating rooms may require different filtration, airflow, and pressure control designs.

Accordingly, the filtration system can be designed in multiple stages. Filters compliant with ISO 16890 can handle pre-filtration and fine dust filtration. For areas with particularly high requirements, additional particulate filters are used.

A particularly challenging example is the operating room. Here, the entire ventilation system must help minimize particle and microbial contamination in the relevant protected area. In such surgical applications, Class H13 HEPA filters, among others, are used for this purpose.

However, the HEPA filter alone does not make for a hygienically compliant HVAC system. Equally important are the airflow pattern, the required supply and exhaust air flow rates, defined pressure conditions between different areas, the hygienic design of the HVAC unit, and good cleaning, disinfection, and maintenance capabilities.

For such applications, HANSA offers the Blue Line Hy, a series of air handling units designed specifically for hygienically sensitive areas. Typical applications include operating rooms and pre-operative rooms, intensive care units, sterile areas, isolation and airlock areas, as well as examination and treatment rooms.

Blue Line Hy units are configured on a project-by-project basis to meet the specific requirements of each application. In addition to the necessary filter stages, the overall concept can include, among other things, heat recovery, cooling and heating, humidification, damper systems, and the required measurement, control, and regulation technology.

Thus, even in hospitals, the goal is not simply to achieve the highest possible filter class. What is crucial is a comprehensive system tailored to the room class, usage, airflow, and hygiene requirements.

What are the filtration requirements in museums?

When providing climate control for museums, consideration must be given not only to visitors but also to sensitive exhibits. Particles

Particles can settle on surfaces and damage sensitive exhibits. Appropriate fine-dust filtration can therefore be part of the protection strategy.

Depending on the location, the outdoor air, and the exhibited objects, gaseous contaminants may also be a concern. Standard particle filters in accordance with ISO 16890 are not designed to capture such gaseous substances in the same way.

In such cases, additional filtration stages—for example, using activated carbon or other suitable adsorbent media—can be part of the air treatment process.

This is particularly evident in museums: Before selecting a filter, it must first be clarified which contaminants are actually to be removed from the air.

How can a multi-stage filtration system be designed?

Instead of handling the entire filtration task with a single filter, multiple filtration stages can be coordinated with one another.

A first filter stage can capture larger particles and already remove a portion of the fine dust load. A second filter stage then takes over the removal of the remaining fine dust. For specialized applications, additional stages—up to and including particulate filtration—can be added.

As a guideline, filters such as those with a rating of ISO ePM10 ≥ 50% can be used at the supply and exhaust air inlets, although ISO ePM1 ≥ 50% represents a higher-performance solution. For a second supply air filter stage, for example, filters ranging from ISO ePM1 ≥ 50% to ISO ePM1 ≥ 80% or higher may be considered. The advantage of a multi-stage filter design lies not only in the

The advantage of a multi-stage filtration concept lies not only in the achievable air quality. An upstream filtration stage can also protect downstream high-quality filters and components from rapid contamination.

The filter stages must be considered as an overall system in terms of separation efficiency, filter area, pressure drop, service life, and maintenance.

Why does filter design affect energy consumption?

Every filter generates a pressure drop. This resistance must be overcome by the fans of the HVAC unit and thus affects the electrical energy consumption.

It is not only the filter class that is relevant. Filter area, design, airflow velocity, and the increasing loading condition during operation also influence the pressure drop.

High filtration efficiency should therefore not be achieved at the expense of an unnecessarily small filter area and correspondingly high air velocities. When designing the unit, filter efficiency, available installation space, pressure drop, and expected service life must be considered together.

Particularly with multiple filter stages, it is therefore not only the initial pressure differential of a single filter that is relevant, but also the pressure drop of the entire filter system over the course of its subsequent operation.

How can you tell when a filter needs to be replaced?

During operation, particles accumulate in the filter and its flow resistance changes. A typical method of monitoring is therefore to measure the differential pressure before and after the filter. The MSR and control technology can be used to record filter conditions or corresponding alerts, visualize them, and transmit them to higher-level systems.

Using measurement and control technology, filter conditions and corresponding alerts can be recorded, visualized, and transmitted to higher-level systems.

However, differential pressure is not the only criterion for a filter change. Depending on the application, the hygienic condition, operating conditions, service life, and the specifications for the respective filter must also be taken into account.

When replacing a filter, more factors than just the filter class must be considered. Dimensions, design, and the filter type specified for the specific HVAC unit must also be taken into account.

Where can you get the right replacement filters for a HANSA air-handling unit?

For an air-handling unit supplied by HANSA, it is known which filter types were intended for the respective unit. This knowledge of the unit can be used during subsequent system operation for the supply of replacement parts.

Through HANSA etaTECH, suitable replacement filters for existing HANSA air-handling units can be offered and delivered. This means operators do not have to determine the required filters solely based on dimensions, filter classes, or old product designations.

This is particularly helpful for older units, where filter products or designations may have changed over the years. The key factor is that the replacement filter matches the existing air handling unit and its filter design in terms of dimensions, design, and technical properties. What is the most important factor overall when designing the filters for an air handling unit?

What is the most important factor overall when designing a filter for an air-handling unit?

The question of the correct filter class is not the first step in the design process. First, it must be clarified what role the filtration is intended to play within the overall ventilation concept.

The following questions, among others, are relevant for the design:

• What are the particle and pollutant levels in the outdoor air?
• What supply air quality should be achieved?
• Is the goal to protect people, products, processes, or equipment?
• What regulatory and hygienic requirements apply?
• What filtration is required on the outdoor and supply air sides?
• What filter quality is required on the exhaust air side to protect the components?
• What contaminants can be carried from the room or process into the exhaust air?
• Is there a possibility of air transmission between the exhaust air and supply air?
• Is the system using recirculated air or mixed air?
• Is single-stage or multi-stage filtration required?
• Are HEPA, activated carbon, or other specialty filters required?
• What is the pressure drop over the entire service life?
• How are the filters monitored, maintained, and later replaced?

HANSA therefore considers filtration to be an integral part of the project-specific design of the entire HVAC unit. The requirements range from conventional comfort ventilation for offices and schools to industrial process air and on to demanding laboratory, cleanroom, and hospital applications.

During subsequent system operation, etaTECH can handle the supply of suitable replacement filters for HANSA air-handling units. This ensures that the process is managed from the initial filter design through to filter replacement throughout the system’s lifecycle.

The housing of an air-handling unit is much more than just a casing for fans, filters, heat exchangers, and other components. It must be mechanically stable and as airtight as possible, minimize heat loss and thermal bridges, and reliably protect the built-in components from external influences.

The appropriate housing design depends heavily on the specific application. An indoor ventilation unit for an office has different requirements than a large air-handling unit on a building roof, a swimming pool unit in a corrosive environment, or an air conditioning unit for a data center.

At HANSA, the enclosure of the air-handling unit is therefore designed on a project-specific basis along with the entire unit. In addition to the dimensions, other factors such as profile and panel design, thermal properties, corrosion protection, weather protection, materials, and color schemes can be adapted to the project’s requirements.

What functions does the housing of an air-handling unit perform?

Depending on the design, different pressure, temperature, and humidity conditions prevail inside an air-handling unit. At the same time, the housing must support the installed components, provide access for maintenance, and guide the air through the unit as controlled as possible.

The essential functions of the housing therefore include:

• ensuring the mechanical stability of the entire air-handling unit
• Limiting deformation under positive and negative pressure
• minimal air leakage
• thermal insulation of the unit’s interior from the surrounding environment
• Reducing thermal bridges and the risk of condensation
• Protection of the built-in components
• Corrosion protection appropriate for the environmental conditions
• Weather protection for outdoor installation
• Accessibility for inspection, cleaning, and maintenance

The requirements are not the same for every unit. That is precisely why the enclosure design should already be an integral part of the air-handling unit design.

Why is the stability of the housing important for an air-handling unit?

During operation, the housing of an air-handling unit is subjected to varying pressure conditions. Depending on the position of the fans, individual areas of the unit may be under positive or negative pressure. These loads must not cause impermissible deformation of the housing.

As the unit size increases, mechanical stability becomes particularly important. Large unit cross-sections and panel surfaces place higher demands on the frame construction, panels, and their connections.

HANSA therefore places particular emphasis on a stable housing design. The housing profiles used were tested and evaluated at the Institute for Materials Testing and Structural Preservation in Oldenburg, among other things, with regard to their compressive and flexural tensile strength.

The high-quality housing design achieves Class D1(M) for mechanical strength according to DIN EN 1886. D1(M) is the highest class in terms of permissible deflection and thus stands for a particularly dimensionally stable housing construction.

However, the frame profile alone is not the sole determinant of stability. The panels must also be designed according to their size and load capacity.

How can enclosure panels be adapted to large devices?

HANSA uses double-shell enclosure panels. The two shells are firmly connected to each other, and the space between them serves, among other things, to accommodate thermal insulation.

Depending on the panel size, installation position, and the expected mechanical loads, additional reinforcements can be provided in this gap. The stability of a panel can thus be specifically adapted to the respective unit design. This means it is not necessary to use only an unmodified standard panel for every unit size and every application.

This means it is not necessary to rely exclusively on a single, unmodified standard panel for every unit size and every application. Especially with large air-handling units, the structure can be reinforced where it is required due to the dimensions and pressure conditions.

The importance of such a scalable enclosure design becomes apparent when dealing with high airflow rates. HANSA has already built air-handling units with air flow rates exceeding 62,000 m³/h, for example, for the DC4 data center in Lithuania.

What role do airtightness and seals play?

A sturdy housing should also have as little air leakage as possible. Leaks can cause treated air on the pressure side to escape from the unit or unwanted ambient air to be drawn in on the suction side.

High-quality HANSA housing designs can achieve leak class L1(M) in accordance with DIN EN 1886.

To ensure a tight seal, double-lip EPDM seals, among other components, are installed in the profiles. In addition to their sealing function, such seals are also suitable for more demanding operating conditions, such as when resistance to aging, cleaning agents, or disinfectants is required.

Doors, removable panels, feed-throughs, and other openings must be included in the sealing concept for the entire unit. Especially in the case of large pressure differentials, it is therefore not only the panel itself, but also the structural design of the entire enclosure that is crucial.

How are heat loss and condensation on the housing reduced?

There can be significant temperature differences between the air inside an air-handling unit and its surroundings. The housing must therefore be adequately thermally insulated.

Depending on the unit model, HANSA uses different aluminum frame profiles and wall thicknesses. In addition to 30-mm versions, 50-mm versions are also available. If necessary, thermally separated and insulated profiles can be used.

For high-quality enclosure designs, in accordance with DIN EN 1886, it is possible to achieve, among other things, a heat transfer coefficient of Class T2 and a thermal bridge factor of Class TB1.

A good thermal bridge factor is particularly important where significant differences in temperature or humidity occur between the interior of the unit and the surrounding environment. This helps reduce the risk of critically low surface temperatures and the associated condensation problems; .

Which profile and panel design is actually required depends on the operating and environmental conditions of the specific project. Not every air-handling unit automatically requires the most technically sophisticated enclosure design.

What distinguishes the housing of an indoor unit from that of an outdoor unit?

When installed indoors, the air-handling unit is largely protected from direct weather exposure. When installed outdoors, however, the housing itself becomes a key component of the weather protection for the entire system.

Rain, wind, moisture, sunlight, and fluctuating outdoor temperatures must therefore be taken into account already during the design phase. Weatherproof HANSA units are additionally sealed accordingly.

Weatherproof HANSA units are additionally sealed accordingly. To ensure controlled drainage of rainwater, the unit can be designed with a curved roof featuring overhangs on all sides and a drip edge. Additional insulation of the roof improves the unit’s thermal and acoustic properties.

Design details such as the sealing of panel joints, doors, and penetrations are also important. A weatherproof air-handling unit is therefore not created simply by adding a roof to a standard indoor unit. Why must corrosion protection be suited to the application?

Why must corrosion protection be tailored to the application?

Moisture and corrosive components in the ambient air can put a strain on the housing and components of an air-handling unit over many years of operation. The extent of this strain depends heavily on the application and installation location.

For standard indoor applications, therefore, a different selection of materials and coatings may be appropriate than for a unit in an industrial environment, near the coast, or in a swimming pool.

HANSA can adapt the housing design to these conditions. In addition to coated sheet steel, depending on the application, for example, stainless steel or aluminum versions are available. For particularly demanding requirements, housings and internal components manufactured by HANSA can be designed with corrosion protection up to Class C5-H. Aluminum components can also be appropriately protected or anodized

Aluminum components can also be appropriately protected or anodized in highly corrosive environmental conditions.

Corrosion protection should not be limited to the externally visible enclosure surfaces. The decisive factor is which materials and surfaces inside and outside the unit actually come into contact with the respective atmosphere.

Why do swimming pools place special demands on the enclosure?

Swimming pools are a particularly clear example of application-specific corrosion protection. The warm, humid air and chloride-containing components place significantly higher demands on materials and surfaces than many traditional comfort applications.

For the Pool Line units from HANSA, the housing and unit design are therefore tailored to these special conditions. Components manufactured by HANSA are protected accordingly against the corrosive swimming pool environment; in addition, joints and seams inside the unit are sealed.

This further illustrates why the housing design should not be considered in isolation from the area of application. A technically suitable swimming pool unit requires not only appropriate dehumidification and heat recovery technology, but also materials and design details that are engineered for this specific environment.

Can the color of an air-handling unit be customized?

For air-handling units installed in visible locations, in addition to the technical specifications, the design of the housing can also play a role. This applies, for example, to units on rooftops, next to buildings, or within architecturally designed technical areas.

HANSA offers options for custom coating of the housing components. This allows for the implementation of various color schemes and enables the units to be adapted, for example, to the design of a building or to the client’s specifications.

The coating serves more than just an aesthetic purpose. Depending on the chosen coating system, it can also make a significant contribution to the required corrosion protection.

Color schemes and technical surface protection can therefore be planned together, rather than treating color as a purely aesthetic detail only after the completion of the unit design.

How customizable can the housing of an air-handling unit be?

Standardized housing sizes make economic sense if the project requirements are compatible with them. In many AHU projects, however, constraints arise that necessitate a more customized design. For example, these may include limited technical space, unusual

These may include, for example, limited technical space, unusual unit cross-sections, transport routes, high airflow rates, specific maintenance access points, or special requirements regarding corrosion, hygiene, and outdoor installation.

HANSA designs its customizable air-handling units using the AirCalc design program. This allows the dimensions and configuration of the unit to be determined on a project-specific basis, rather than selecting exclusively from a fixed grid of predefined standard units.

This flexibility also applies to the housing. Depending on the project, the following properties, among others, can be customized: unit dimensions and geometry:

• Unit dimensions and geometry
• Profile and panel design
• Wall thickness and thermal properties
• Additional reinforcements within double-skin panels
• Materials and surfaces
• Corrosion Protection
• Weather Protection and Roof Design
• Color schemes
• Doors and maintenance access points
• Modular Design for Transport and Installation

This principle is not only applied to the Blue Line series. For the Pool Line and the Free Line series as well, adapting the housing design to the application, unit size, and installation conditions plays an important role.

What does a large air-handling unit reveal about its housing design?

The larger an air-handling unit becomes, the more evident the importance of a stable and customizable enclosure design. As the cross-sectional area increases, the panel surfaces and doors grow larger, while at the same time, high air flow rates and the resulting pressure conditions must be controlled. A practical example is the HANSA units installed for the DC4 data center in Lithuania. There, eight large Blue Line IT cooling units were installed.

A practical example is the HANSA units installed for the DC4 data center in Lithuania. There, eight large Blue-Line IT cooling units were installed, each with an air flow rate of 62,200 m³/h.

For transport, the units were designed in segments so that no extra-wide transport would be required. This example thus illustrates two aspects of custom unit design: A housing must be sufficiently stable during later operation and, already during design and manufacturing, take into account the requirements for transport, installation, and assembly.

What are the key factors to consider when selecting an air-handling unit housing?

The housing design should not be determined only after the other components of an air-handling unit have been selected. It is an integral part of the overall unit design.

Key questions include:

• What are the dimensions and airflow capacities of the air-handling unit?
• What positive and negative pressures occur inside the unit?
• What level of mechanical stability is required?
• What are the airtightness requirements?
• What temperatures and humidity levels occur inside and outside the unit?
• How important are thermal insulation and the thermal bridge factor?
• Will the unit be installed indoors or outdoors?
• What level of corrosion exposure is expected at the installation site?
• Are there any special requirements due to hygiene, industrial use, or a swimming pool environment?
• What access points are required for inspection, cleaning, and maintenance?
• What transportation and installation options are available?
• Should the housing be color-matched to the building or surroundings?

At HANSA, these requirements can be incorporated into the enclosure design as early as the equipment specification phase. Sturdy frame profiles, double-walled panels that can be further reinforced if necessary, various thermal designs, and customizable corrosion and weather protection make it possible to tailor the enclosure to the actual operating conditions.

A good AHU enclosure is therefore not simply a shell surrounding the air-handling components. It is an integral structural component of the unit that combines stability, airtightness, thermal properties, durability, maintainability, and protection of the entire system.