PLC Programming for HVAC

We will discuss about "Input and Output Signals" in this section. You can understand what the basic of function block diagram is. And you will see the practical examples of input and output signals for HVAC control systems.

We will study about the definition of "Constants and Variables". You can understand about how to process analog signals to use PLC program in this section. And you will see how to do simulation and how to check your program with a basic human machine interface (HMI) provided by the freeware, CODESYS V3.5 development.

We need to figure out how to operate equipment for operating HVAC control system properly. In this session you can see how to deal with digital output (DO) signals which are used for AHU (Air Handling Unit), ACCU (Air Cooled Condensing Unit), EDH (Electric Duct Heater), EHU (Electric Humidifier Unit), Fans, motorized dampers, motorized valves, interface signals and so on. Software simulation with HMI will give you clear picture of the automatic system’s operation.

In this section, you will see how to use timer which is one of favorite function blocks for automatic engineers. We will discuss how to use an on delay timer for configuring alarms. There is a program example including simulation of it.

We will figure out how to handle analog output signals in this section. We will check the PID function block (FB) for dealing with a feedback loop with analog output signal. After taking this section, we will understand how to use PID FB properly. And there is an example for programming and doing simulation for operating a VFD (Variable Frequency Drive) AHU.

To control the room temperature we use a TCV (Temperature Control Valve) for chiller systems. In this section we will find out how to control a TCV with PID controller. You will see an actual example for programming and simulation.

What if you need to add some critical alarms such as fire alarm, emergency shutdown switch and so on? This section will let you know how to add them easily and simply. There is a programming example and its simulation. You will be able to understand what the interlock is and how to build it with PLC program with this section.

More and more systems becomes integrated nowadays. We need to know how to make the HVAC control system interact with other systems properly. We will check the typical interface signals of HVAC control systems for industrial facilities. There is a practical example for you to do programming and simulation.

Now, it is time to learn how to operate many devices or equipment in a harmonic way. You will get introduced about building programs easily and simply but satisfyingly. There is a practical programming example with its simulation.

There are lots of special functions. And sometimes we need to add one of them to make your HVAC control system versatile. In this section we will discuss about the re-circulation mode used for an industrial solution actually. After taking this lecture, you can understand what the re-circulation mode is and how to build programs for it by yourself.