Knowledge base
Every remote radiator and dry cooler moves its air with axial fans, and today the choice is between two families. AC fans have an induction motor that runs at a speed fixed by the mains frequency, controlled, if at all, by a frequency converter or by switching fans on and off. EC fans - electronically commutated - have a permanent-magnet motor with its own electronics in the hub, speed-controlled by a signal, and are the newer family. This guide compares them on the points that matter for a radiator: control, power, noise, price and the site.
How Each One Works
An AC axial fan is an induction motor with an impeller on its shaft. On a 50 Hz supply a four-pole motor turns at a little under 1,500 rpm, on 60 Hz a little under 1,800 rpm, and that speed is what the fan delivers unless a frequency converter sits in front of it. Control without a converter is on-off: fans are started and stopped in stages as the coolant temperature rises and falls.
An EC fan has a brushless permanent-magnet motor and a controller built into the motor housing. It takes the mains supply, rectifies it and drives the motor at whatever speed a 0 to 10 V or a bus signal asks for, from standstill to maximum, continuously. The electronics also give it a higher efficiency than an induction motor of the same size, report its own status and faults, and let one controller run a whole row of fans at the same speed.
Power At Part Load: Where The Difference Is
On the design day both families draw about the same power for the same airflow. The difference is every other day. The fan laws say the power falls with the cube of the speed: a fan at 70 % speed draws about a third of its full-load power. A radiator sized for 50 °C that runs most of the year at 30 °C needs far less air than its fans can deliver, and a speed-controlled fan takes exactly as much as the coolant temperature asks for. Over a year of prime or continuous operation the saving on a radiator with a dozen fans is measured in tens of megawatt-hours.
AC fans reach the same result with a frequency converter, which adds a panel, cabling and the converter's own losses, and converter-driven AC motors need insulation and bearings rated for it. On-off staging saves power too, but in steps, and the switching cycles wear the contactors and the motors.
Noise, Price And The Site
Because the sound power of a fan falls by around 15 dB when its speed is halved, speed control is also the quietest way to run a radiator at part load, and the way to meet a night-time limit without stopping the plant. EC fans make this continuous and simple; AC fans with a converter do the same with more hardware. At full speed the two families are equally loud.
EC fans cost more per fan, and the electronics in the hub are sensitive to the surroundings: the ambient temperature rating, the protection class against dust and water, and the quality of the supply - voltage spikes, harmonics - are checked for the site. On a 60 Hz / 480 V supply, on a hot or dusty site or where the owner wants the simplest possible machine, AC fans are still a sound choice; on a noise-limited, part-load or energy-conscious installation EC fans pay for themselves. TECS fits both families and selects the fan at the site density, voltage and frequency for every design.
In Short
- AC fans: induction motor, fixed speed, staged on-off or converter control, robust and cheaper
- EC fans: permanent-magnet motor with built-in electronics, continuous speed control, higher efficiency
- Power falls with the cube of the speed: speed control saves most at part load
- Halving the speed takes about 15 dB off the fan noise
- EC electronics need the right ambient, protection class and supply quality
- TECS selects either family at the site density, voltage and frequency
What To Send With An Enquiry
- Power supply: voltage, frequency, and its quality where known
- Operating profile: standby, prime or continuous, hours per year
- Sound limit and distance, day and night if they differ
- Site ambient, dust and corrosion class
- Control interface wanted: 0-10 V, Modbus, contacts
- The usual thermal data: heat, flows, temperatures
Questions We Are Often Asked
Are EC fans more efficient at full speed?
Slightly: the permanent-magnet motor and the integrated electronics give a few percentage points over an induction motor of the same size. The large saving is at part load, where the speed control counts.
Can EC fans run on 60 Hz?
Yes; the electronics rectify the supply and the fan is rated for a voltage range, often both 50 and 60 Hz. The supply voltage and the fan's rated range are checked in the selection.
How are EC fans controlled on a radiator?
A temperature controller reads the coolant and sends a speed signal to all fans of the unit; a 0-10 V signal or a Modbus bus is usual. The control panel can be TECS-supplied or the plant's own.
Do EC fans need a frequency converter?
No; the converter is inside the fan. That is their point: speed control without a separate panel and its losses.
Which family lasts longer?
Both reach tens of thousands of hours with maintained bearings. AC fans are simpler and tolerate a rough supply and a hot site better; EC fans need their electronics kept within the rated ambient and protected from dust and water.
Contact Us
Send us the heat duty, the fluid temperatures and flow rates, the ambient conditions and the installation limits. We answer with a design proposal - or write to us on WhatsApp.
