HVAC stands for “Heating Ventilation and Air Conditioning.” Though this technology is essential to comfortable modern living, it’s far from a single, simple system. There are many complex HVAC system types, each with their own rules, quirks, and standards.
In fact, the only elements that seem to unify all HVAC systems besides the principles they run on and physics of heat exchange might be the amount of dust they tend to collect.
Therefore, to become a successful HVAC technician, you have to have a strong working knowledge of all the HVAC systems as well as HVAC software. Here’s a brief overview of each system to get you started.:
A split HVAC is exactly what it sounds like. As opposed to other HVAC system types, a split system has one part outside of the home or commercial property and the other part inside.
Typically, this means the air conditioning unit is on the outside with a condenser coil, compressor, circuit board and wiring, and a blower fan. Inside, there is a gas furnace for heating – though that is simply one formulation among many.
Which split system is most suitable for a particular install depends on factors like climate, budget, use of space, and any pre-existing ductwork.
For instance, an industrial install for a high school might use a combination of indoor or outdoor air- or water-cooled chillers for their air conditioning and a centralized interior boiler for heating.
In very warm climates, for instance, air-handler-and-heat-pump configuration is sometimes the most sensible since the heat pump handles both heating and cooling. This negates the need for an expensive gas furnace install. However, this type of heating isn't very effective for warming in very cold weather.
On the opposite side of the spectrum, extreme cold weather climates might feature a combination furnace and heat pump as the split HVAC configuration. This also known as a “hybrid heat pump system”. This name comes from heat pump's ability to pull double-duty as an air conditioner in occasional warm weather and aid the ability of a gas furnace to pump out more heat during the coldest months.
As you can see, split systems come in many forms, but they are among the most common HVAC arrangements. If you’ve ever noticed a bulky central air conditioning unit sitting on a wooden platform of a house, you’re looking at one component of a split system.
All the units described so far have been ducted systems using ducts within a home or business’s walls to force warmed or cooled air around the interior space.
But another type of split system is a ductless split system or ductless mini-split. They’re less commonly seen than relatively cheap window air conditioning units or hideaway central air conditioning systems.
You often see them in light commercial use – think bars and restaurants. They're easily identified by their long white rectangular frame and wall-mounting without any apparent outdoor egress aside from a single piece of PVC going into the wall or ceiling.
Ductless split HVAC system types can operate as solely air conditioners or outfitted with a heat pump to provide both heating and cooling.
In some ways, these represent the “middle path” of HVAC systems: They don’t require expensive and labor-intensive items in order to work – hence “ductless” – but many models support up to four indoor units on one outdoor compressor. That includes full control over the four units in each section of the house.
For the consumer – and you can think about this as a tech potentially upsetting a ductless system – the initial investment is likely higher than it would be for a comparable number of window units, but without having to install a full central HVAC system, ductless split systems represent an elegant compromise.
And if you’re feeling like going green and saving a few bucks on your electrical bill long-term, solar-powered ductless mini splits are fast becoming a hot new thing.
Either way, there’s an efficiency factor: no ducts means no ducts can leak.
Then there’s the packaged HVAC system. As the name suggests, a packaged system puts your heating and cooling elements in one big package that sits outside your home.
That means it houses your blower, condenser coils, compressor, evaporator, and heater all in one unit.
Packaged systems are space savers and generally used when a split system isn’t an available option due to space or other considerations. Their main drawback is lower efficiency than these other options with less overall flexibility in configuration and installation.
They also tend to have a shorter shelf-life, since more components of your heating and cooling system can break – necessitating a fix to the whole unit – and they are also continually exposed to outdoor elements.
However, they are popular in commercial installations and are commonly seen as rooftop units. Packaged systems are handy for centralizing the heating and cooling points in a large building when running complex ductwork.
They can also include add-ons like air purifiers and ventilators to help deliver cleaner air to the building before it starts circulating through.
Finally, there’s the geothermal HVAC system type.
This an expensive but extremely efficient HVAC system that requires an “earth loop” buried underground and uses the deeper earth’s naturally cooler and stable temperatures to regulate the HVAC system.
The underground or other natural source provides a heat sink to dissipate heat in the summertime and an insulated heat source to provide heat in the wintertime.
Geothermal HVAC – not to be confused with geothermal electricity – usually requires pipes dug five or six feet deep and uses an underwater aquifer or the ground’s natural cooling to lower temperatures and dissipate heat in the heat exchange system.
The following describes the two primary types of geothermal HVAC systems.
Closed-loop: In a closed-loop system, pipes are buried underground in one of several configurations – vertical, horizontal, or slinky (just like the toy) – and have a mixture of water and antifreeze pumped through them.
As this mixture moves through the cool underground pipes, its heat dissipates and it can be piped back up through the system.
Open-loop: An open-loop system, on the other hand, relies on water for its primary “free” cooling method. Usually, this involves installing a well or other underwater aquifer or using a nearby pond or lake that can transfer thermodynamic energy.
The big benefit of either of these types of geothermal HVAC systems using the earth’s natural cooling is cost-free. You only need electricity to power pumps, the blower, and the compressor.
This is only the barest overview of what you need to know as an HVAC tech. We haven’t touched, for instance, the complexities of single and multi-stage cooling and heating systems. Nor have we discussed Seasonal Energy Efficiency Ratings (SEER) and the benefits of Energy Star rated installs for residential consumers or the different types of refrigerants available for different systems.
Learn more about the certifications and tools HVAC techs need here.