How does my HVAC system work?

Controlling the air temperature and humidity in your home and maintaining high air quality are the basic functions of all HVAC systems. But how?

There are several types of HVAC systems that you may choose from to achieve these results. Some systems are more effective than others, depending on the climate where you live. Let's look at how several different types of HVAC systems work.

Split Air Conditioning System

First, why is it called a "split" air conditioning system? Because it has components that are located inside and outside the home-it's literally split into two pieces. You may have also heard it referred to as "central air."

Consisting of an outdoor unit with a condenser and compressor, and an indoor unit with a fan and an evaporator coil, a split air conditioning system works by removing warm air from your home and cycling it back as cooler air through a system of supply and return ducts. Powered by electricity, the compressor pumps refrigerant through the system to collect heat and moisture inside the home. That heat and moisture is removed from the home when the warm air collected inside the home is blown over the cooled indoor coil, which cools the air. The heat transferred into the coil during this process is pumped outside the home, while the cool air is cycled back inside.

A split air conditioning system is particularly effective in warmer climates, as it effectively keeps your home cool and reduces humidity levels. It also features a lower indoor noise level compared to free-standing air conditioning units, since its compressor-bearing unit is outside of the home. Central air conditioning systems, such as a split system, provide the added benefit of air filtration because, as a "forced air" system, air is drawn out of rooms through air returns and pulled through an air filter. This removes airborne particles and results in cleaner, filtered air being redistributed to your home through air supply ductwork.

Mini-Split/Ductless System

As you likely gather from its name, a mini-split/ductless system is a split system, which means it has components that are located inside and outside the home. However, unlike traditional split HVAC systems, it does not rely on air ducts to route air throughout your home. Rather, a mini-split/ductless system is designed to heat or cool a single room, a zone or an addition to your home that may lack or cannot accommodate ductwork.

A mini-split/ductless system is powered by electricity and comprised of a relatively small outdoor condensing unit and a compact indoor evaporator unit, which hangs on the wall to control and direct airflow. The "mini" in this type of HVAC system's name is a direct reference to the indoor unit's diminutive size and inconspicuous appearance. The indoor and outdoor components are connected via copper refrigerant tubing and electrical wiring, requiring an opening just three inches or less in diameter.

Widely recognized for their energy efficiency and extremely popular outside the United States, where ducted HVAC systems are rare, the mini-split/ductless systems are an excellent option for attics or garages that have been converted to living space, or for home additions that would require extending your existing ductwork.


When you hear the word furnace, you may initially think of old technology like the large "gravity fed" furnaces of the early 20th century. But in modern, forced-air HVAC systems, furnaces feature far more advanced technology and play a larger role in your indoor comfort year-round.

Often matched with split air conditioning systems, today's furnaces not only do a great job of keeping your home warm during the winter, but the furnace fan, or blower, is also used to assist the air conditioning system in circulating cooled air during warmer seasons.

A gas furnace produces heat through the combustion of natural gas in its burner. The heat produced from this process passes through a heat exchanger. Air from your home's return air ducts is blown over the heat exchanger and warms the air. The furnace's blower then blows the warmed air into the ductwork, which carries and disperses it throughout your home.

As part of a forced-air, split system, furnaces benefit from air filtration afforded when air is drawn out of rooms and pulled through an air filter. Whenever the system is running, this cycle repeats, continually filtering and cleaning the air in your home.

Heat Pump/Air Handler

Don't let the name fool you. A heat pump, when matched with an air handler, is an excellent alternative for both heating and cooling your home. Just think of a heat pump as a heat transporter, extracting warm air from your home during the summer, and reversing operation to bring warm air in during the winter. Though it may be difficult to believe that there's enough warmth in outdoor air during the winter to heat your home, there is actually enough heat energy present in 32 degrees Fahrenheit air to keep you warm and toasty inside. However, in colder climates, a supplemental heat source may be required.

A heat pump is installed outside the home, similar to a central air conditioning unit. The unit's compressor circulates refrigerant between it and the indoor air handler, absorbing or releasing heat en route, depending on the season. It does not burn fuel to produce heat; rather, it just uses electricity to move heat into or out of your home. As a result, heat pumps boast less fuel consumption during cooler seasons when compared to gas furnaces. Its matched air handler resides inside the home, contains a coil and blower fan, and serves to circulate conditioned air throughout your home.

A year-round home comfort solution, a heat pump and air handler system is particularly effective in moderate to warmer regions of the country, and does a fine job of maintaining comfortable indoor temperatures and humidity levels. It also offers the air filtration benefits inherent to forced-air systems, because air is pulled through an air filter. This removes airborne particles and results in cleaner, filtered air being redistributed to your home through air supply ductwork.


A thermostat for your home's HVAC system can range from very basic and functional to extremely sophisticated and feature-rich. Generally speaking, the thermostat controls the operation of your entire HVAC system and provides precision temperature regulation. Newer digital, programmable thermostats, such as a ComfortNetâ„¢ Controlling Unit, feature both comfort- and efficiency-enhancing functionality.

For example, programmable thermostats may be set to optimally regulate the temperature in your home, based on your schedule and daily routine. Many offer precise humidity control, the ability to vary the temperature in various zones of your home, and advanced monitoring capabilities. Some programmable thermostats even allow for the remote control of your HVAC system via wireless devices.