Most ventilation fans can be categorized into three types of motors:
- Alternating Current (AC)
- Direct Current (DC)
- Electronically Commutated (EC)
AC motors require AC electrical power while DC motors require DC electrical power.
An EC fan is built with a DC motor but can run on AC, avoiding the need for an AC/DC transformer. EC fans have an integrated Power Control Board (PCB), which transforms incoming AC power into DC.
This guide explains what all of that means and explores the pros and cons of AC, DC, and EC motors.
If you aren’t familiar with the differences between alternating and direct current, this video is a good crash course.
What are AC motors?
AC motors require higher input voltages in the range of 110V-240V. They either can be hardwired in an electrical line or run directly from a standard outlet, which supplies AC power at different voltages depending on where you are in the world.
- In North America, the standard is 120V alternating current (also referred to as 120VAC) with a 60Hz frequency.
- In Europe, the standard is 230VAC with a 50Hz frequency.
Many AC motors are rated for 110V/50 Hz but will also run on 120V/60 Hz without any impact on the longevity of the motor’s internal components. In most power grids, fluctuations of +/- 6% are considered normal and the vast majority of electrical appliances are designed to handle such variations without any issues.
What are DC motors?
DC power isn’t available from a standard electrical outlet, so DC motors require a DC power supply to covert the current and voltage to the required specs.
Like with AC voltages, a direct current input voltage of 12V or 48V can be stated as 12VDC or 48VDC, respectively.
Compared to AC motors, DC motors have lower input voltages. In order to use standard wall outlets, AC power must be transformed into DC power using a converter, reducing the voltage from 120VAC/230VAC to something in the 3-48VDC range.
That’s exactly what your laptop’s power adapter does. Laptops run on various voltages of DC, and your adapter converts your wall outlet’s AC power to the DC power your laptop needs.
What are EC motors?
AC motors use AC power.
DC motors use DC power.
EC motors use…EC power?
Nope (because EC current isn’t a thing).
Though EC looks like it has the same naming convention as AC and DC, it actually stands for “Electronically Commutated.” That won’t clear things up if you don’t know what “commutate” means, so let’s define that.
Commutate: to reverse every other half cycle of (an alternating current) so as to form a direct current
In reality, an EC motor is just a DC motor with a built-in Power Control Board (PCB) that converts AC power from your standard wall outlet to the DC required by the motor.
Advantages and Disadvantages of Each Motor Type
This is a good time to look at the pros and cons of each motor type.
Because IndoorGrowTech is geared toward indoor growing, we’ll focus on AC, DC, and EC fans, but each has broader applications than just ventilating an indoor growing space. Consider the following applications:
- Vertical farming
- Server rooms
- Garages and other poorly-ventilated workspaces
Which motor is best for each application? Let’s evaluate the advantages and disadvantages of each.
AC fans are the most common type of fan on the market.
Advantages of AC Fans
1 | They don’t require an external power supply, which allows them to be hardwired into household electrics.
2 | They come in a wide range of available designs and are easier to manufacture, which leads to lower prices compared to DC or EC fans.
Disadvantages of AC Fans
1 | AC motors are far less efficient than both DC motors and EC motors, which means higher operating costs for fans with comparable specs. AC motor efficiency hovers around 60%, which means about 40% of the electricity consumed by the fan doesn’t transfer into air movement. DC or EC motor efficiency is closer to 90%. This 30-point difference makes AC fans 4x less efficient and results in wasted power consumption and hundreds of dollars in extra spending over the fan’s useful life, especially if it’s used every day.
2| AC motors have issues with speed modulation, which is regulated by power input. AC power can’t be adjusted as easily as DC, so AC motors require special speed controllers. The most common speed controllers for AC fans are variable rheostats, which have the following limitations:
- They can manipulate voltage but not amperage.
- They can decrease fan speeds (RPM) by 10-40% of the maximum value but can’t go lower.
- Decreased RPM results in an unpleasant humming noise due to excessive amperage applied to the motor (remember, variable rheostats can’t reduce amperage).
- They don’t result in a proportional reduction in power costs.
You can opt for a more expensive stepdown transformer—called a thyristor—which can manipulate both voltage and amperage. However, the cost of such transformers often matches or exceeds the price of the actual fan, making them cost-prohibitive in many applications.
DC fans have been on the market for a while, but they primarily were built to be small and used for applications such as CPU and electronics cooling. Only recently has technology advanced to where building 10″, 12″, 14″, and 16” DC fans is both feasible and economically viable.
Advantages of DC Fans
1 | They have lower energy consumption, especially at less than maximum power, which means more energy savings and lower operating costs. Over the course of their useful life—approximately 5+ years—those savings far outpace the price difference between AC and DC fans, making DC fans a much better long-term investment thanks to better energy-efficiency.
2 | DC motors with advanced electronic boards are capable of working with many types of speed controllers. They can receive PWM, 0-10V, and potentiometer speed controller signals, provide tachometer output for monitoring, and operate flawlessly with programmable thermostats, building management systems, and other types of customized controls often used in industrial applications.
3 | Many brushless DC motors are built with a frameless magnet design, which minimizes wear and tear and extends its useful service life beyond that of AC fans.
Disadvantages of DC Fans
1 | Because DC motors require DC power, you can’t plug them into a standard wall outlet. They need to be hooked up to an external DC power supply.
2 | DC and EC motors contain costly electronic components and are manufactured in smaller quantities, which gives them higher initial price points than similarly-sized AC fans.
Electronically commutated (EC) fans use EC motors, which are just brushless DC motors that include an external circuit board and the ability to run on both AC and DC power. They share the same advantages and disadvantages as DC fans above, plus a few more of their own.
Advantages of EC Fans
1 | They don’t require an external power supply to convert AC power into DC. Instead, that’s handled by a built-in circuit board called the Power Control Board (PCB), which increases or decreases the DC voltage supply to achieve the desired motor speed. A computer chip on the PCB circuit board accepts the signal from the fan’s speed controller—either PWM, 0-10V, or potentiometer format—and interprets it into the corresponding voltage to achieve the desired RPM
2 | Because EC motors can convert AC power to DC, they offer the advantages of DC fans with the convenience of AC fans. You can plug them right into your standard wall outlet.
3 | ECMF fans, like those made by TerraBloom, can be used with wireless remote controllers. Wireless control is useful for fans installed in hard-to-reach places, thermostat controllers, or for automated programmable fan operation modes.
Disadvantages of EC Fans
1 | They’re the most expensive type with higher costs than similarly-sized AC and DC models. Whether the added convenience EC fans offer is worth the higher price point is a personal decision but, in most cases, an EC fan is the right option—especially for indoor growing setups looking to use standard AC wall outlets.
AC, DC, and EC Motor FAQ
The descriptions above are simple to make it easier for you to choose the best inline fan for your application. For additional information, here are some questions I’m asked frequently about the various types of motors.
What are brushless motors?
Brushless DC motors, also called BLDC motors, use magnetic fields to power rotation. They have four primary parts:
- Stator: The stationary part of the motor with three components itself: the stator frame, stator core, and stator windings. The windings are wound coils connected to a power source to generate a magnetic field.
- Rotor: The part that rotates inside the stator. In a brushless DC motor, the rotor is encased in a permanent magnet. As the stator generates a magnetic field, the rotor’s magnets interact with the stator field to create its own rotor field, which causes the rotor to spin and powers whichever element is supposed to move. In the case of fans, fan blades are mounted on the rotor, which in turn circulates the air.
- Sensor: Monitors the rotor’s position and sends signals to the controller.
- Controller: Uses inputs from the sensor to activate the stator windings in a structured way to create a rotating magnetic field to spin the rotor.
“Brushless” motors are more advanced versions of “brushed” or “simple” motors that have neither a sensor nor controller. Instead, brushed motors use conductive carbon brushes and a commutator ring to control the current applied to the stator windings (among other structural changes). Brushless motors eliminate brush friction, giving them better performance and higher efficiency.
While brushless AC motors exist, most of the time we’re talking about brushed DC motors.
What are induction motors?
Rotors on induction motors have conducting plates that interact with the stator’s magnetic field, which causes the rotor to spin and induces a magnetic field of its own—hence their name.
Any time we’re talking about induction motors, we’re talking about AC induction motors, also called three-phase inductor motors, because DC induction motors are physically impossible. Induction requires a varying magnetic field created by a variable frequency drive (VFD) powered by alternating current (AC). You can’t create a varying magnetic field with direct current (DC).
While both brushless DC motors and AC induction motors are similar in operation, each using stator cores and rotors that move without being mechanically connected, they have two key differences:
- Brushless DC motors have less heat generation, which means fewer energy losses.
- Brushless DC motors have better peak efficiency.
There’s another type of AC induction motor which does have permanent magnets mounted to the rotor: the creatively-named permanent magnet AC motor (PMAC). PMACs offer more precise rotation control, which isn’t required for inline fan applications.
What’s the most energy-efficient motor?
Energy-efficiency is an important consideration, especially if you plan to run the motor frequently (such as with most ventilation applications). When used a less than maximum energy output, DC and EC motors require less energy input, making them more energy-efficient and cost-effective options.
Inline Fan Motor Types: Final Thoughts
Which motor should power your inline fan? Here’s a quick summary of everything above:
- AC Fans: Lowest initial cost but higher recurring operating costs and more expensive in the long run. Inefficient and limited speed control that produces a loud hum, especially at lower speeds. Biggest benefit is convenience as they either can be plugged into standard power outlets or hardwired into household electrics.
- DC Fans: Higher initial cost than AC fans but more energy-efficient and a better long-term investment. Better speed control. Require an external DC power supply.
- EC Fans: Highest initial cost but combine the best features of AC and DC fans—the convenience of running on standard household AC power with great energy-efficiency and long-term cost-effectiveness.
For ventilation applications that require near-constant use, the choice comes down to DC and EC fans. If you have access to an external DC power supply, go with a less-expensive DC fan. If not, go with an EC fan and enjoy both hassle-free installation and long-term energy-efficiency.
To learn more about the different fans available, and the manufacturers I trust most, check out our complete guide on How to Choose the Best Inline Fan.