July 9, 2025
Understanding HVAC System Components: A Homeowner’s Guide
Curious about what’s behind your HVAC system? This guide breaks down the key components of an HVAC system, like heat exchangers, coils, and control boards, so you can better understand how your system works and when it might need attention.
Key Takeaways
- There are two main residential HVAC setups: one with a furnace and air conditioner, and one with a heat pump that handles both heating and cooling.
- Key components include the heat exchanger, evaporator coil, condenser coil, blower motor, thermostat, control board, and capacitor.
- Heat pumps use a reversing valve to switch between heating and cooling without generating heat like a furnace.
- The thermostat sets your desired temperature, but the control board is what activates the system components.
- Blower motors, ducts, and filters all affect how efficiently and cleanly air moves through your home.
- Knowing how your system works can help you recognize problems early, understand repair quotes, and extend the life of your system.
If you have ever wondered how HVAC systems work or what’s actually going on behind your thermostat, you are not alone. Most people don’t take the time to see how the system works until something goes wrong. Whether you have a heat pump or a more traditional HVAC setup with a furnace and air conditioner, there are a handful of components doing the heavy lifting behind the scenes.
Knowing what various HVAC system components are and what they do can help you spot issues sooner, and understand what your technician is talking about when it’s time for a repair or replacement.
Let’s Start With the Basics
There are two main types of residential HVAC setups:
- One that uses a furnace and air conditioner
- One that uses a heat pump, which can both heat and cool
The parts you’ll find in either system can vary, but the core idea is the same: move air, heat or cool it, and send it around your home.
Furnace and Heat Exchanger
If you have a furnace, it’s likely what heats your home in the winter. Inside that furnace is something called a heat exchanger, which is where the actual heat transfer occurs.
The heat exchanger warms up, and air blows over it. That warm air then gets pushed into your home. It’s a critical part, if it cracks or gets damaged it can cause serious safety problems which is why technicians always check it during a tune-up.
Evaporator Coil and Condenser Coil
These two work as a pair when it comes to cooling your home.
- The evaporator coil lives inside and absorbs heat from your indoor air.
- The condenser coil is outside and gets rid of that heat
Evaporator coil vs. condenser coil?
Think of one pulling heat out of your home, and the other sending it away.
What If You Have a Heat Pump?
A heat pump is kind of like an AC that can run in reverse. It uses a part called a reversing valve to switch from cooling to heating depending on the season. Instead of generating heat (like a furnace does), it moves heat from one place to another. Heat pumps still use a condenser, evaporator coil, blower motor, and thermostat, just a little differently. If you don’t have a furnace and your outdoor unit runs year-round, you probably have one.
Blower Motor
The blower motor moves air. It pushes air across the coils or heat exchanger and into your ducts. If it goes out, the rest of your system might still be working, but no air is reaching your rooms.
Thermostat vs. HVAC Control Board
The thermostat is the control on your wall, it doesn’t actually run anything. When you turn it up or down, it sends a signal.
The control board is what makes things happen. It’s a circuit board inside your system that receives that signal, figures out what’s needed (heat, cooling, just the fan), and then turns on the right components in the right order.
If your thermostat seems fine but your system does not respond, it could be a control board issue, as opposed to a thermostat issue.
HVAC Capacitor
HVAC capacitors help to jump-start major parts of your system; usually the blower motor or the compressor. It stores energy and releases it quickly. If it’s worn out, your system may hum, click, or just not start. Capacitor replacement cost? Usually between $100 and $250, depending on your unit.
Ducts, Vents, and Filters
Your ducts carry air in and out of your rooms. Supply vents push air out while return vents pull air back into the system. And then there’s the filter, which keeps dust and debris out of your equipment. A clogged filter not only makes your air dirtier but it can cause system damage and higher bills making it important to regularly swap out your filters.
So…How Does It All Work?
In short:
- You set the temperature on the thermostat
- The control board gets the message and tells the system what to do
- Air is pulled in, heated or cooled, then sent back out through the vents
- The cycle repeats until your home hits your selected temperature
Heat pump or furnace, it’s the same basic flow. Only the method of heating changes.
Why Understanding the Parts of an HVAC System Matters
Understanding your HVAC system components can help you:
- Catch small issues before they turn into major repairs
- Make sense of quotes and recommendations
- Ask better questions
- Save money in the long run
Need Some Help?
If you’re not sure what system you have, or if something just feels off, our team at Mint Home can take a look. We offer fast free online quotes tailored to the needs of your home. We also offer a MintCare maintenance plan to help you make sure your system is always ready to operate at peak performance.
Additional Resource
Want to learn more about heating and cooling systems in general? Check out the U.S. Department of Energy’s HVAC page for a breakdown of system types and efficiency tips.
