What to Know About HVAC Control Systems  

February 18, 2021

The HVAC industry is on the rise, predicted to leap from $13.6 billion in 2018 to $27 billion in 2023. From investors to everyday decision-makers, it’s worth following the trends on this issue. After all, even homeowners will be impacted by this. We’ll look at the basics of these systems, including their foundation of equipment, sequences, and priority controls.

What Is an HVAC Control System?

An HVAC control system refers to the components that produce the results of your heating, ventilation, and air conditioning. At a basic level, the thermostat would be considered a control system because it’s how an operator changes the temperature of a home or building.

The thermostat is not only relaying a message to the equipment to shut off when it achieves certain conditions, but it’s also quantifying the temperature of the ambient air before doing so. Again, this is the most simplistic example. If you were discussing the HVAC control system of a 300-classroom school, the operation (and system) would be on a very different scale.

Automation at Home

As with everything else in the modern world, automation is becoming a valued friend for homeowners that want to maximize efficiency. For larger homes or buildings, the HVAC controls are sometimes folded into a larger energy management system.

As with HVAC systems, these systems are customized to the structure. For some, automation might include everything from burglar alarms to lighting to sprinkler systems. HVAC would be just one of several functions that are looped into the main control center.

There’s a couple of schools of thought on this. Some people love the consolidation. It allows for better data collection and makes it easier to integrate artificial intelligence. These smart homes and offices have the capacity to become ruthless machines — ensuring that not one ounce of energy is wasted.

Others wonder if it’s too risky to count on one system. Should it fail for any reason, the consequences would be catastrophic. It’s a debate that we’ll likely be having for a while, but it does help to know how standalone control systems work before considering how it does or doesn’t apply to home or building automation.

Sequence of Events

Like most complex machinery, HVAC control systems are built to be logical. If you set the temperature at 80° F, you want the thermostat to sense the average temperature of the air and then use that input to control the equipment.

In a home, your thermostat adjustment passes through a sensor. From there, the temperature will control the air conditioner to kick on when the temperature reaches over 80° F and kick off again once it’s equal or lesser to 80° F.

These statements have a lot to do with how your equipment performs, which in turn has everything to do with comfort and utility bills. What’s known as ‘dial-in sequences’, like those described above, are also what ensures we don’t have to manually adjust the machinery every time there’s a particularly warm or cold day.

Types of Equipment

There are a few key types of equipment that you should know about for HVAC control systems:

  • Network infrastructure: In an HVAC control system, there are usually two cables. They’re twisted together and responsible for different input and feedback. The CAT-5/6 Ethernet cable takes messages back and forth from computer software to controllers and the RS-485 cable relays messages between the controllers and the devices.
  • Head-end software: This is the software that dictates how the operator uses the system. It’s the interface that shows them the data and the hub for the operator to make changes.
  • Controllers: The controller is any device connected to the network infrastructure that will either monitor or fully control the end device.
  • End devices: Devices that detect variables, such as humidity or temperature. They can also be relay switches or actuators that convert energy.

From the air condition unit to the activated circuits that are turned on and off, the equipment needed in an HVAC control system can be extensive. The end goal is to streamline all of it so there are fewer hiccups along the way.

Priority Control Systems

A control system is programmed to respond to commands differently, depending on what the commands are. For instance, in a nuclear plant, an operator might be able to override system controls in an emergency just by pushing a single button.

For the most part, it’s programs that dictate the course of a standard day. This might look like a daily or weekly set of commands, depending on the circumstances. For instance, maybe you set the HVAC system at a different temperature when you know the home will be unoccupied.

In this case, it’s the operator that has the highest level of control, meaning an authorized party can make changes based on what’s happening. For instance, let’s say that a homeowner is leaving for two weeks. Even though they’ve programmed a weekly temperature schedule, they can change the settings for the time they’ll be gone in order to conserve energy.

Every control system has its own layers of logic built-in, and usually a few priority levels too. This is what gives people the flexibility they need to adjust the system so they’re not beholden to a pre-determined set of controls.

Benefits of a Control System

An HVAC control system is considered an effective way to control all of the air in a home or building. It can help eliminate those packets of cold air or that one spot that’s constantly overheating. At newACunit.com, we’ve watched the evolution of HVAC systems.

Our staff has worked hard to identify which equipment will help homeowners reduce their energy bills while still keeping everyone comfortable. If you’re interested in learning more about upgrading or installing one, contact us today to see how we can help.

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