On the website for your region you will find information on the products relevant to you, contact details and news.
Unfortunately, there is no Greek language version of our website. However, you can stay on this page or contact our sales representative in Greece directly.
A clear understanding of fan performance and its verification is essential for delivering reliable and energy-efficient air systems. This begins with fan aerodynamic performance test methods, which provide a consistent way to measure airflow, pressure, and efficiency under controlled conditions. Building on this, product certification plays a critical role in ensuring that the tested performance is independently validated and meets recognized industry standards, giving confidence to both designers and end users.
Another key aspect is wire-to-air performance, which reflects the true overall efficiency of the fan system by considering all energy losses from the electrical input to the actual air output. In addition, modern applications increasingly require flexibility, particularly in AHU retrofit projects, where space constraints and existing system limitations demand adaptable solutions.
Finally, understanding real duty point flexibility ensures that the selected fan can operate efficiently across varying conditions, rather than only at a single design point, supporting long-term performance and energy savings.
Aerodynamically, fans can be measured in different ways, as described in ISO 5801. The standard defines several measurement types depending on the inlet and outlet conditions of the fan.
Applicable to all fan types. Efficiency is calculated based solely on the static pressure increase, representing the basic air performance of the fan.
The outlet duct has the same cross-section as the fan housing. This configuration is commonly used for scroll housing fans, as it allows efficiency to be calculated using total pressure on the discharge side, often resulting in a higher efficiency value.
The inlet duct matches the fan housing cross-section. This setup is less common and typically used only for special axial fans.
Both inlet and outlet have the same cross-section as the fan housing. This type is frequently used for axial fans, especially high-pressure models where the discharge air velocity is high, leading to a higher total pressure increase and improved total efficiency.
It is essencial to select the appropriate measurement type according to ISO 5801 when evaluating or comparing fan performance.
Recalculating performance data from one measurement type to another is not straightforward and requires additional measurement points.
Test Rigs
Regular Certification
Fan Selection Software
Regular Certification
Production Processes
Regular Certification
Third-party certifications provide customers with greater confidence in a product´s performance, quality, and reliablity. They serve as an objective assurance that the product meets recognized industry standards.
Test Rigs - Regular Certification
(e.g., AHU manufacturer associations, Eurovent, AMCA, VDE, etc.)
Fan Selection Software - Regular Certification
(e.g., AHU manufacturer associations, Eurovent, AMCA, VDE, etc.)
Production Processes - Regular Certification
(e.g., ISO standards, AHU manufacturer associations, AMCA, etc.)
“Wire-to-air performance data” are important because they show the total efficiency of a fan system - from the electrical power input (wire) to the actual air performance output (airflow and pressure).
Wire-to-air gives a true picture of energy consumption, which is crucial for system designers and end-users focused on total operating cost.
Shaft-to-Air is ideal for fan-to-fan comparisons, but it does not reflect motor or drive losses, so it can be misleading if used alone.
Aspect | Wire-to-Air Performance | Shaft-to-Air Performance |
| Definition | Total system efficiency from the electrical input at the power source (wire) to the air output (delivered airflow and pressure). | Efficiency from the fan shaft mechanical input to the air output. |
| Scope | Comprehensive - includes all losses: motor, VFD (if used), belt/drive, bearings, and fan. | Partial - includes only losses within the fan itself and any direct drive components. |
| Includes | Motor efficiency + VFD losses + Belt/gear losses + Fan aerodynamic losses. | Only the fan´s aerodynamic efficiency. |
| Measurement Point | Start point: electrical power at the wire terminal. | Start point: mechanical power on the fan shaft. |
| Example Systems | EC plug fan with integrated electronics or belt-driven fan with separate motor and VFD. | Bare fan tested in a lab according to AMCA/ISO standards. |
| Industry Standards | AMCA 208 / ISO 13348 often specify wire-to-air for real-world efficiency ratings. | AMCA 210 / ISO 5801 typically specify shaft-to-air efficiency. |
| Real-World Relevance | Directly reflects what the customer pays for in electricity. | More theoretical - good for comparing fan design, but incomplete picture. |
| Accuracy for Energy Use | High - represents the real power draw from the electrical grid to the airflow delivered. | Limited - does not reflect actual energy usage, only aerodynamics fan efficiency. |
| Footprint & Space Planning | Reveals true efficiency of compact systems, like multiple EC fan arrays. | Does not highlight system-level advantages of modern designs. |
| Decision-Making | Useful for selecting high-efficiency systems and justifying premium options like EC fans. | May lead to wrong investment decisions if interpreted as total efficiency. |
Aspect | Wire-to-Air Performance | Shaft-to-Air Performance |
| Installation | Modular, easy to bring in sections though access doors | Large, needs major dismantling or crane |
| Space Adaptability | Flexible layout fits into light AHU space | Rigid layout, hard to adjust |
| Operation Flexibility | Individual speed control & staging | Single-speed or limited VFD control |
| Redundancy | One fan failure - others still run | Single failure - full system down |
| Energy Efficiency | Excellent at part-load; optimized airflow | Less efficient at partial load |
| Maintenance | Replace 1 fan while system runs | Requires full shutdown for service |
| Noise & Vibration | Low noise, balanced operation | Higher vibration & noise |
| Future Expandability | Add/remove fans as needed | Fixed capacity |
Even if a fan is perfectly selected on paper, the actual operating point (airflow and static pressure) can differ from the design duty point due to several real-world factors:
1. System sesistance deviation
2. Air density and environmental conditions
3. Manufacturing tolerances and measurement errors
4. Control system or speed setting differences
5. System aging and operational conditions
In most AHU retrofit and variable-load AHU applications, multiple smaller EC fans are usually better than a single axial fan with a VFD - but it depends on priorities (efficiency, turndown, redundancy, space, cost, sound).
Better real-world (wire-to-air) efficiency across operating range
EC fans combine motor and electronics optimized for the fan - they keep efficiency high at partial speeds, where as a single AC motor and VFD often loses some efficiency at low speeds and though VFD and motor losses.
Wider, smoother turndown with good efficiency
You can stage fans (1, 2, 3…) and also vary each EC fan´s speed to match loads with fine granularity - giving very efficient performance from low to high loads.
Built-in redundancy / reliability
If one fan fails, the AHU can still operate (reduced capacity) - critical for comfort/critical spaces. With a single fan, failure would mean the whole AHU shutdown.
Easier matching to shifted system curve
Multiple fans let you change number of active fans and speeds to track the actual system curve after installation or as systems foul.
Improved part-load noise control
Running fewer fans at higher but efficient speed can sometimes be quieter than running one oversized fan at low inefficient speed - depends on fan selection and acoustics.
Smaller mechanical footprint and easier handling
Smaller fans are easier to install and replace; often fewer structural changes required.
Fan selection and curve matching
Market Segment Management (Building)
Sarinya Theeravanichkul
sarinya.theeravanichkul@ziehl-abegg.co.th
Andre Mueller
andre.mueller@ziehl-abegg.com
