EC or AC fan: The EC fan gives us more options and is more efficient

In HVAC, fans, and air curtains, the terms EC and AC are used frequently. They often make it sound as if these terms alone explain whether a fan is good, efficient, or modern. It is not quite that simple.EC and AC first describe the motor technology. For an airwall, however, the motor alone is not decisive. What matters is whether the fan delivers the required pressure, the right air volume, and the correct discharge velocity for the specific opening.

That is why SAW-Airwalls primarily uses fans with radial impellers. In a compact design, they can provide the static pressure required for air guidance, the nozzle, and stable air separation. Conventional air curtains, by contrast, are often designed around different fan concepts and lower pressure requirements. We explain the fundamental differences between an airwall and an air curtain in a separate article.

Only the interaction between motor, impeller, air guidance, nozzle, and control system creates an effective and economical system.

This article therefore explains more than the difference between EC and AC motors. It also shows why radial fans, speed control, and correct system design are often more important for airwalls than the simple question of whether the data sheet says EC or AC.

EC and AC: how important are these abbreviations?

What does EC mean in fans?

EC stands for “electronically commutated.” Strictly speaking, this does not describe the fan itself, but the motor technology.

In practice, EC motors are often brushless DC motors, also known as BLDC motors. BLDC stands for “brushless direct current.” These motors do not have mechanical brushes that switch the current inside the motor. Instead, this task is handled by electronic control.

This electronic switching is called commutation. It ensures that the windings in the motor are energized in the right sequence and that a rotating magnetic field is created.

Many EC fans can still be connected directly to an AC power supply. The required electronics are already integrated into the motor or motor unit. For the operator, the fan therefore behaves like an easily connected device, even though an electronic motor control system is operating internally.

Many modern EC fans use external rotor motors. In this design, the outer part of the motor rotates around the stationary stator. The impeller can be connected directly to the rotor. This creates a compact motor-fan unit, which is often useful for radial fans used in airwalls. External rotor describes the motor design, not the airflow direction of the impeller.

The advantage of EC motors is therefore not only motor efficiency. It is also important that EC fans are usually easy to control. The speed can be adjusted to the actual demand. This matters for airwalls because not every opening, weather condition, and operating situation requires the same air performance.

What does AC mean in fans?

AC stands for “alternating current.” AC motors are operated with alternating current and have been used for many decades in industry, ventilation, and HVAC.

Conventional AC motors, especially asynchronous motors, are robust, proven, and suitable for many applications. Many existing airwall systems also operate reliably with AC motors.

In AC motors, the change in current direction comes from the AC power supply. The voltage changes polarity regularly, for example 50 times per second in the European power grid. This creates an alternating magnetic field in the motor, which enables rotary motion.

In conventional AC motors, the speed depends mainly on the supply frequency, the number of motor poles, and — in asynchronous motors — the slip. If the speed of an AC motor needs to be controlled, a frequency inverter is often used.

The frequency inverter changes the electrical frequency and thereby enables speed control of the motor. This means that an AC fan can also be operated according to demand.

AC is therefore not automatically outdated or poor technology. For airwalls, what matters is whether the motor, fan, control system, and air guidance fit the application. EC motors often have advantages today in compact design, integrated control, and part-load operation. AC motors with frequency inverters remain useful in certain systems, larger power ranges, existing installations, or special applications.

EC or AC: what is the practical difference?

The difference lies mainly in the type of control, speed regulation, and integration.

EC/BLDC fans often already have electronic commutation and control integrated into the motor unit. They are usually easy to control steplessly and are very efficient, especially at small and medium power levels and in part-load operation.

AC motors are robust and proven alternating-current motors. They can also be controlled, but in many cases they require a frequency inverter. This is technically sound and has long been proven in industrial systems. However, it means additional components, more wiring, and proper coordination between the motor, frequency inverter, and fan.

For airwalls, the decisive point is therefore not whether a motor is called EC or AC. What matters is whether the motor-fan unit delivers the required pressure and air volume and can be controlled appropriately for the application. For many new airwall applications, EC/BLDC fans are advantageous today. AC motors with frequency inverters remain useful for existing systems, larger power ranges, and special cases.

Why the impeller is just as important as the motor

EC and AC describe the motor technology. But the motor alone does not create an effective airwall. It drives the impeller. Only the impeller generates the air volume and pressure required for air guidance and the nozzle.

This distinction is important for airwalls. An airwall does not simply have to move as much air as possible. It has to create a directed, stable air jet that reliably shields an opening. For this, the fan needs not only air volume, but also sufficient static pressure.

What is a radial fan?

In a radial fan, the air is usually drawn in axially and discharged radially, meaning sideways outward. Modern radial fans can also discharge air forward. Radial fans can build up comparatively high static pressure in a compact design.

This pressure is needed to move the air through housings, ducts, deflections, and nozzles. If the pressure is insufficient, no stable air jet reaches the opening. Air volume alone therefore says little about whether a fan is suitable for an airwall.

For airwalls, this point is decisive. The air has to be guided to the nozzle, accelerated there, and discharged at the opening as a stable air jet. That is why SAW-Airwalls uses radial fans.

What is an axial fan?

In an axial fan, the air flows through the impeller along the motor axis. The air is therefore moved in an axial direction. Axial fans can move large air volumes and are used in many ventilation and cooling applications.

Their strength is often air volume. If air needs to be moved over short distances with low pressure loss, an axial fan can be very useful.

Depending on their design, conventional air curtains use different fan concepts, for example tangential fans and axial fans. In many cases, the focus is on a uniform airflow across the width of a door. For airwalls with higher pressure requirements and targeted nozzle guidance, this perspective alone is not sufficient.

EC, AC, radial, or axial: what is the better solution for airwalls?

The difference between an airwall and a simple air curtain is therefore not only the motor. What matters is the complete system consisting of motor, impeller, fan housing, air guidance, nozzle, and control.

The question is not simply EC or AC. For us, it is also clear: radial, not axial.

An airwall has to reliably shield an opening. For this, it needs more than air volume. It needs a stable, directed air jet. The decisive factors are air volume, static pressure, discharge velocity, controllability, efficiency, and the installation situation.

EC/BLDC radial fans

For many new airwall applications, EC/BLDC radial fans are particularly interesting today. They combine efficient brushless motor technology with good controllability and a compact motor-fan unit.

Radial fans can provide the static pressure required for the housing, air guidance, and nozzle. EC/BLDC motors also enable simple speed control and good adaptation to different operating conditions.

This combination is particularly suitable for airwalls that do not have to run permanently at full output, but can be controlled according to demand.

AC motors with frequency inverters

AC motors with frequency inverters remain useful. They are robust, proven, and have been used in many industrial applications for decades. Many existing airwall systems also operate reliably with AC technology.

AC solutions can still be the right choice, especially for existing systems, larger power ranges, special designs, or existing infrastructure.

Radial fans or axial fans

Axial fans can move large air volumes and are very useful in many ventilation applications.

For airwalls, however, pure air volume is often not enough. If the air has to be guided through housings, deflections, and nozzles, the required static pressure is decisive.

Axial fans are less expensive, but so far we have not found one that meets our requirements.

What does SAW-Airwalls prefer?

SAW-Airwalls primarily uses radial fans because airwalls require a defined air jet with sufficient pressure. In new systems, EC/BLDC radial fans are often the preferred solution when compact design, good controllability, long operating hours, and efficient part-load operation are important.

This does not mean that AC motors are wrong. The application is decisive. An existing AC system can operate reliably and economically.

The best solution is therefore not the fan with the most modern abbreviation, but the correctly designed airwall.

Why system design is more important than the abbreviation on the data sheet

EC, AC, radial, and axial are important technical terms. But they do not decide on their own whether a fan is suitable for an airwall.

For SAW-Airwalls, the specific operating point is decisive. The fan must provide the required air volume, the necessary static pressure, and the correct discharge velocity. At the same time, power consumption, noise, installation space, controllability, and installation conditions must fit the application.

Speed plays an important role because it influences air volume, pressure, and power consumption. However, this relationship does not apply only to EC/BLDC fans. AC motors can also be controlled with a frequency inverter.

In simplified terms, the following applies to fans: air volume changes roughly in proportion to speed. Pressure changes roughly with the square of the speed. Power consumption changes roughly with the cube of the speed. This means that a change in speed can have a major effect on function, noise, and energy consumption.

For selection, we use the design and configuration programs of our fan suppliers, for example ebm-papst and ZIEHL-ABEGG. These tools allow fans to be checked based on characteristic curves, efficiency, power consumption, speed, sound values, and operating point.