How the actuators work in HVAC and AHU Systems

How an actuator works in HVAC and AHU (Air Handling Unit) Systems

An overview of what an actuator is and how it is integrated into an Air Handling Unit

The importance of the actuators in the HVAC systems and AHU units

The development of the HVAC systems and AHU's plays a key role in empowering the units to process multiple tasks simultaneously to deliver the required outcome. Air Handling Units are the devices in charge of managing the circulation of the air. The core part of the AHU is the control, and how it manages the various control components to regulate the different values of the air. The actuator is one of the control components, it is specifically the tool that physically executes the actions requested by the control. The role of the actuator in the control system is focused on the regulation of airflow.

What is an actuator device? 

The AHU actuator is the part in charge of moving a specific mechanism in order to regulate the airflow inside the HVAC system. Opening and closing a valve, or regulating the flow of the air through a duct are two examples of what an actuator does. 

The actuator is managed by the AHU controls, which read the values of the air (ie. CO2 levels, differential pressure etc.) and then send an input signal to the actuator. The main source of energy to execute its mechanical actions is the electrical current.

Values to check in an actuator

At the moment of deciding the actuator to use for a specific AHU, it is important to check the following specifications to understand what the actuator requires to work and the level of service it provides:

Supply Need, Voltage: this value shows the electrical current required to supply the actuator. The main values are:

24 V

230 V

Dual Voltage 24..240 V

Torque, Actuation Force: this refers to the strength of the actuator applies to execute its action, for example opening and closing a valve. 

Control type: the control type is related to how the actuator performs its action.

Open/Close: the actuator is able to only perform full actions without any middle regulation, for example, full opening or fully closing of a damper or valve.

Modulating: the actuator is able to perform its action at different positions between open and close. For examples, partially opening the valve or damper to 60% rather than just fully closed (0%) or fully open (100%)

Safety Function: the ability of the actuator to automatically revert to a fixed position (normally fully closed or fully open) when there is an emergency such as a power failure. 

Running Time: the time required for an actuator to perform its action, for example to either fully open or close a damper or valve.

Types of actuators in AHU's

There is a wide range of AHU actuators that differ for specifications and applications, it is important that the specific type fits and is compatible with the AHU system. 

These tools differ for the part of the AHU system that they control:

Damper Actuator: it is the device designed to manage the opening and closing of the Damper in an air conditioning system.

Valve Actuator: it is the device designed to manage the opening and closing of the Valves in an HVAC system.

The type of movement that the actuator executes define the version:

Linear Actuator: it performs the movement following a straight line

Rotary Actuator: it performs a rotatory movement.

Also, the actuators differ for being equipped with a spring or not:

Spring-Return Actuators: these devices perform their activities with the use of a spring to complete the activity when there is a loss of power.

For example, on power failure, the actuator will automatically revert to a  fully closed/open position thanks to the mechanical spring function

Fail-safe Actuators: These tools have a mechanism that helps the actuator to keep running when, for any reason, there isn’t enough power supply. A capacitor is installed into the actuator and discharges the stored energy to a motor, at this point the actuator is led to either a fully open or closed position.

What is a damper actuator?

In an Air Handling Units, a damper actuator is designed for the management of the air, specialising in the regulation of the damper. 

What does a damper actuator do?

In the ventilation and HVAC systems, these Industrial damper actuators manage the airflow by either opening, closing or regulating the damper. In this way, the actuator defines the amount of air entering from the outside. 

How do you size an actuator for a damper?

In this file provided by Belimo, who are one of the top worldwide manufacturers of actuators for HVAC, are described they outline , they provide 10 questions to answer in order to understand what actuator is required for your damper following the specifications of your system:

Size of the damper

Position of the damper blade

Presence of edge Seals

Torque

Air Velocity and Static Pressure

Fail-safe requirements

Supply Voltage

Control Signal Type

Required additional accessories

Actuators and Sensors as parts of the HVAC system

The sensors and actuators cooperate in the same AHU system even though their functions and competencies are different. In a few words, the sensors monitor the relevant environmental conditions, receive physical inputs and turn them into electrical signals to send to the Air Handling Unit.

The actuators receive the electrical input from the controller and turn it into a mechanical motion in order to manage the airflow.

Types of damper actuator

The types of damper actuators are based on the ability to modulate the opening and closing of the damper. Each motorised damper actuator is defined by their capacity to regulate the flow as follow:

The Open/Close Damper Actuator is able to manage the flow of the air in 2 positions: fully open and fully closed.

The Belimo LF230 Open/Close Actuator is an example, it is a device suitable for dampers that either fully shut or open the blades.

The Modulating Damper Actuator manages the flow of the air at different levels.

The Siemens GDB161.1E Modulating Damper Actuator is another example of an actuator that sets the damper aperture at different positions.

What is a valve actuator?

The Valve Actuators are the accessories that mechanically execute the aperture of the valve. In the cooperation between valve and actuator, the latter receives a power supply to run actions focused on either opening, closing or regulating the valves. The electronically controlled valve, then, plays a key role in the management of the flow.

These actuators are part of the Automatic Control Valve, a valve in charge of managing the flow of the fluid following the controller inputs and composed of three main parts:

• Control Valve Positioner
• Control Valve Body
• Control Valve Actuator

The type of control valve actuator required depends on the shape of the valve, whether it is a ball, butterfly or globe valve. Each valve and actuator needs to be chosen carefully following their compatibility.

Types of the valve actuator

The types of valve actuators differ for the mechanism that they use to move the valve:

The Electric Valve actuators are supported by an electrical power source, a battery.

The Belimo LR230A is a Valve actuator that uses an Electrical power supply to work.

Another example is the Siemens GMA321.9E, an Electromotoric actuator designed for ball valves.

What is a spring return actuator?

There are different types of actuators, either valve or damper, that are equipped with a spring return. This spring is required to support the actuator when there is a loss of power and it is not able to terminate its action of opening/closing either valve or damper. When the actuator is stuck in the middle, with no energy to process the task, the spring pushes it in order to return to its original position.

The Belimo LF24-SR is a 24v electric actuator with spring Return integrated to support the device when there is any power supply issue.

Linear actuator vs rotary actuator: how they work and related differences

The motion of the actuator is another important aspect to consider. The type of movement to control the damper and the valves define the actuator itself and make it suitable for specific applications.

What does a linear actuator do?

The AC Linear Actuators and DC linear actuators apply a straight movement to complete their task. They are fitted with a linear electric motor, regulating the aperture of dampers and valves in an AHU system.

Types of linear actuator

The Belimo LH24A-MP100 is a damper linear actuator 24V that follows a straight motion to manage the aperture of the dampers.

The Belimo LV230A-TPC is an Electric linear Actuator that is compatible with globe valves and applies a linear movement to push the valve.

What does a rotary actuator do? 

The Rotary Actuators follow a rotatory motion to regulate the airflow into the HVAC system.

Rotary actuator working principles

The actuator turns the energy into a physical rotation, this specific motion is called Torque and it creates the required pressure to influence the course of the fluid/airflow.

Types of rotary actuator

Here are two Rotary actuator examples:

The Belimo SM230A is a Rotary actuator for dampers that rotates to operate a complete shut or opening of the damper blades.

The Siemens GSD141.1A is a compact Rotary actuator for dampers, its rotating movement manages the regulation of the damper.

Conclusion

In this article, we have provided an overview of what an actuator is, how it works and the applications in an HVAC system and an AHU unit. All the types of actuators here mentioned are available in their specific category, the main brands in we stock are Belimo and Siemens.

If you want to add anything relevant related to the topic or your direct experience, feel free to leave a message, we would like to hear from you.

If you need any additional info and details do not hesitate to contact us at support@i-acs.co.uk