What Are the Key Parts of an HVAC System?

HVAC Logo IconBy Tom MoorAugust 16, 2023
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Most homeowners are satisfied with their heating and air conditioning systems as long as they keep their homes comfortable and safe year-round. However, when issues arise, they are often at a loss due to the system's complex configuration and numerous components.

Gaining an understanding of the diverse parts of an HVAC system and how they collaborate to regulate temperature, humidity, and indoor air quality offers valuable insights about how your heating and air conditioning system works.

Key Elements of HVAC Systems

Just like the intricate components of a vehicle work together to propel it forward, HVAC systems contain various parts to regulate indoor temperature and air quality effectively. The main parts of an HVAC system include:

The Main Unit

Traditional HVAC systems incorporate central air conditioners, heat pumps, furnaces, or boilers as their primary heating and cooling units. While the classic configuration involves a combination of a gas furnace and a central air conditioner, the adoption of heat pumps is growing due to their capacity to provide both heating and cooling for year-round comfort.

With modern technological advancements, the most efficient air-source heat pumps can operate effectively even in temperatures as low as zero degrees Fahrenheit. However, mid-range or budget models may require a supplementary heating source, such as gas furnaces, when temperatures drop below freezing.

Other types of HVAC systems include ground-source heat pumps, ductless mini-splits, window or portable ACs, and space heaters.


The thermostat serves as the “brain” of your home's HVAC system. It controls when your heating and air conditioning system turns on and off based on your preferred settings. Thermostats are centrally located for convenience and are positioned away from direct sunlight and heat-generating appliances to ensure accurate readings.

Depending on the type of thermostat you buy, you can either control it manually (manual thermostat), preset the temperature based on the day of the week and time of day (programmable thermostat), or change it remotely from your smartphone (smart thermostat). Smart thermostats can use geofencing technology to automatically adjust the settings based on the location of your smartphone.

Air Handler

The air handler, situated indoors, houses the necessary HVAC components for circulating conditioned air throughout homes or buildings and maintains a critical role in maintaining a comfortable indoor environment. It contains several key HVAC components, including the blower, the blower motor, the air filter, and the evaporator coil.

Evaporator Coil

The evaporator coil is a crucial component of an air conditioning and heat pump system. It facilitates cooling by absorbing heat from indoors as a refrigerant passes through it, causing the refrigerant to evaporate. As the warm air contracts the cold coil, moisture in the air condenses on the coil's surface, contributing to dehumidification while the cooled and dehumidified air is then circulated back into the indoor space.

Heat pumps, meanwhile, use the evaporator coil in heating and cooling modes. During the heating mode, the heat pump's evaporator coil extracts heat from the outside air and transfers it indoors through the process of refrigerant compression and condensation, effectively warming the indoor space.

Condenser Coil

Integral to central air conditioning and heat pump systems, the condenser coil resides within the outdoor condenser unit (the big box next to your home). It collaborates with the indoor evaporator coil to regulate indoor temperatures. Throughout the cooling cycle, the condenser releases heat absorbed from indoor environments to the outdoor air.

The proper functioning of the condenser coil during heat transfer is imperative for overall system performance and efficiency. The condenser coil should be cleaned at least once a year by a qualified HVAC technician during an HVAC tune-up.

Heat Exchanger

While central air conditioners and heat pumps operate by transferring heat between the indoor and outdoor spaces for cooling, a gas furnace relies on an interior heat exchanger to generate warmth. Located inside the furnace, the heat exchanger absorbs heat from the combustion gases and transfers it to the surrounding air. This heated air is then distributed through ductwork to provide warmth.

Annual furnace maintenance ensures the entire heating system, including the heat exchanger, is operating properly and is in good condition. Cracks in the heat exchanger can potentially lead to the emission of harmful gases such as carbon monoxide into living areas, leading to health concerns and potential hazards.


The ductwork is responsible for transporting conditioned air across a home or business and distributing it in living or working areas through air vents. Ducts are typically located out of sight between walls or in the attic. Regular inspections are necessary to ensure the absence of any leaks which could lead to a loss of conditioned air which can raise energy costs and lead to increased system wear and tear.

How to Care for Your HVAC System

Now that you know about the essential components of a heating and air conditioning system, ensuring it receives regular care and maintenance will help reduce untimely breakdowns or premature system replacement. Some DIY tasks to perform include:

  • Having regular maintenance performed. HVAC systems require regular maintenance to ensure efficient, reliable operation, as well as reduce issues from developing. A reputable HVAC technician should tune up the heating system in the fall and the cooling system in the spring. They will inspect, clean, and calibrate all necessary components and uncover any minor issues and recommend the needed repairs.
  • Changing air filters. Your HVAC air filter catches contaminants such as dust, pet dander, and other allergens from recirculating throughout your HVAC system. Clogged and dirty filters can restrict airflow which can cause reduced system performance and even a complete breakdown. Change filters about every two months or according to the manufacturer's guidelines.
  • Clearing the area around your AC condenser. Ensure your outdoor air conditioner condenser unit is free of any debris such as leaves and twigs to ensure efficient airflow and proper operation.
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