Understanding the Components of your HVAC System

Your HVAC system is as important to the health and comfort of your family as the air the system cycles. HVAC stands for Heating, Ventilation, and Air Conditioning, and just as those three terms cover a wide array of capacities and variables, the system requires an array of components to function at its most efficient levels. There are some of these components that you will interact with on a daily basis, and others you may never have the chance or opportunity to work on or handle. Here are the general components most every HVAC system utilizes, and what each component does to keep your system functioning effectively.


The thermostat is the component, the piece, that most homeowners are readily familiar with. It is often the most visible part of your HVAC system. Usually set on a prominent wall that is easily accessible by you and your family, there are a variety of options and models available to best fit your family’s needs. Some are programmable, and some can be set manually. This component, once set to the desired temperature, communicates with your system’s heat exchanger or evaporator coil-condensing unit to begin circulating warmer or cooler air as needed to maintain the temperature in your home.


The furnace is one of the most important components in your HVAC system. And like many important things, it also requires a lot of space – often, the furnace is placed in cellar, basement, attic, or specially-designed closet. The furnace heats a supply of air which is then distributed throughout the home. This heating process is made possible through one of four possible heat sources: combustion, electric resistance, heat pump, or solar energy. Combustion in particular utilizes either natural gas, oil, coal, or propane in a controlled system to produce the necessary heat.

Heat exchanger

The heat exchanger is inside the furnace itself. This component activates when the furnace is alerted by the thermostat to produce warmer temperatures. The heat exchanger pulls cool air into the furnace, heats it, and then shunts the resulting warmed air into the house via the ductwork and vents. In other words, the heat exchanger is the brain of the furnace.

Evaporator coil

The evaporator coil is the exact opposite of the heat exchanger. This component acts to cool air when your thermostat is set to a lower temperature than the ambient air in your home. Located in a metal enclosure on the exterior surface of the furnace, usually either the top or side walls, the coil functions in a way similar to an automobile radiator to produce cooler air.

Condensing unit

The condenser is connected to the evaporator coil. This unit is installed by an HVAC contractor on the outside of your home and is filled with a refrigerant gas. When the refrigerant is cooled to a liquid state by heat exchange with the exterior air, the condensing unit pumps the liquid into the evaporator coil to be warmed to a gas once more.

Refrigerant lines

These lines run between the evaporator coil and condenser, transporting the liquified or gaseous refrigerant in a constant cycle. Often manufactured from copper or aluminum, these narrow tubes are essential to the successful cooling of your home.


This term refers to the system of ducts and shafts that transports the warmed or cooled air to the different rooms in your home. These components are often made of lightweight aluminum, but they can also be manufactured from steel, flexible plastic, polyurethane, fiberglass, or even fabric.


Vents sit on the end of the ducts where they enter the various rooms of your home. Often rectangular, they are made of high- and low-temperature safe metals, and are usually placed on or near the ceiling. Many are also made with angled slats (“vents”) on the front of the panel, which direct the heated or cooled air down into the rooms. Many models can be closed or adjusted to restrict or increase the flow of air from the ducts into the rooms.

Maintain your system

Some components can be checked and maintained by yourself as the homeowner. Others, such as the condenser and evaporator, furnace, and ductwork, should only be repaired and serviced by a trained expert. Metro Express Services is here with highly skilled professional technicians ready to help you when you need us. Give us a call today!


Randy Murphy

Randy Murphy has been building his knowledge of the air conditioning and heating business for several years now. He first started applying his knowledge while working for his father’s HVAC company. Later, in 1987, Randy started his own business: Metro Express Service. He has been a top 10 Trane & Amana dealer for over eight years. When it comes to heating and cooling, Randy knows the business better than anyone.
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