Getting to Know your Actuators: A Breakdown

An actuator is nothing more than a device that makes something move or operate, but with it comes a wide range of shapes, applications, and energy sources to be utilized. We run into examples of various types of actuators throughout multiple industries every day. Today we will go over the categories of actuators, breakdown a few of them that pertain to the HVAC industry, and hopefully, give you a better idea of how they work/how they can be applied.

Hydraulic

Let’s start with Hydraulic actuators. These consist of a fluid that uses hydraulic power to facilitate mechanical motion/operation. The construction and transport industries see a fair share of hydraulic actuators. This is because of sheer power and lack of “give” within fluid-based devices common in those fields. They utilize pressurized fluid to generally operate at forces over 500 PSI. They also are handy in scenarios that require a great deal of accuracy.

Pneumatic

Pneumatic actuators are pressurized with air or gas and are in many small engines, sensors, and switch applications. The control signal is powered by an electric compressor and measures the pressure output to adjust the valve or valve stem inside the actuator. This adds motion to the application needed. These generally stay around the 100 PSI or less range to operate consistently.

Some HVAC dampers operate on spring return actuators and offer 2-position or 3-position control. They operate by using spring force on one side to either open or close the valve. The pressure created on the spring creates the opposite motion. The spring return is best for applications where you might need to shut down quickly.

Piezoelectric

Probably the least common linear actuator you’ll run into is the piezoelectric actuator. In short, these actuators act off electrical charges stored within materials like ceramic to expand an object to its desired state. They can handle extreme pressures of multiple tons with high accuracy down to the subnanometer. Use these when the job calls for a scientific study, aeronautics, telescopes, and more common examples like a guitar amp pickup or electronic drums.

Mechanical

Finally, we’ve reached the most common and most important type of actuator within the HVAC industry. By far the most frequently used is the mechanical or electromechanical actuator. Simply put most operate off converting rotary motion into linear motion to operate the application in need. The major distinction between mechanical and electromechanical comes down to power sources like a motor or hand crank. These are usually low-pressure devices compared to hydraulic or piezoelectric actuators but offer a wide range of mechanisms to reach the desired range of motion. In HVAC zoning these are critical devices for accuracy in damper systems to open and close to the desired setpoint.

Mechanical in HVAC

Automated zone controls almost always require some sort of mechanical actuator to operate a damper. How these actuators achieve this can come in a wide variety of options. Modulating actuators work with a standard range of motion in damper controls, usually completely open or closed. They come in 3 main variants: Analog, Pulse Width Modulation, and Floating Point.

Analog modulation is regularly utilized for simple control signal outputs that only require 3 basic ranges of motion. Powered by .5-10 VDC, 2-10 VDC, or 4-20 mA output these devices signal the damper to close, half-open, or completely open.

Pulse width modulation allows control over digital outputs with a periodic digital output waveform signal. This modulation form is handy in power control but typically utilized for measurement purposes. Benefits like no-loss transmission, high precision, and low power usage make it a useful form of modulation.

A floating-point signal uses two VAC outputs to drive the actuator toward open and the other close. How it works is you have a float sequencer that understands the control signal as a variable between 0-100% input. The float sequencer will control the device using two outputs represented with clockwise or counterclockwise.

We covered a lot of the basic forms of actuators available and hopefully, this clarifies how they can be applied throughout the HVAC industry. Though mechanical/pneumatic actuators represent the bulk catalog within HVAC, it helps to understand the other types to explain how they work within our industry. Check out our collection of actuators and let us know if you have any questions about this topic.