Whether you’re dealing with dry desert heat, sticky southern summers, or frigid northern winters, your HVAC system is key for your comfort and safety.
That being said, it can also seem like it’s full of foreign objects and may have components outside, inside, and on top of your home. Plus, some parts may be hidden inside floors and walls, and likely have sensors, gauges, motors, and electrical panels.
Below, we’ll explain the basics of your HVAC system, so you can identify its main parts and know when it needs professional attention.
HVAC basics
HVAC stands for heating, ventilation, and air conditioning. Your system creates the desired climate inside your home by warming, cooling, venting, and humidifying or dehumidifying the air.
Almost all homes have these HVAC components:
- A heat or cooling source
- A distribution system
- A ventilation system
There are tons of different HVAC systems. We already covered cooling systems in our ultimate guide to air conditioning, so for this post, we’ll explain the two most common categories of heating systems. The basic concepts should apply to any system. Then, we’ll cover distribution and ventilation in general.
Your home’s heating
Your heat source is the heart of your HVAC system. It’s the equipment that actually generates the heat (or cool air in the case of air conditioning systems) for your home. It’s usually located in the basement or in a utility closet inside your home.
There are two main types of heat sources: Furnaces and boilers. Both use gas, oil, or electricity to create heat. So what’s the difference?
Furnaces, also known as forced-air systems, heat air and use a blower fan to distribute it throughout your home using ductwork and vents (more on this in the distribution section below). They typically have:
- A filter that needs to be changed monthly during heating season
- An on-off switch to cut power to the unit (if it doesn’t have an on-off switch, flip the breaker to turn it off
- A switch to reset the motor if it malfunctions
Boilers, technically known as hydronic heat systems, heat water and pump it through pipes to different parts of your home. Unlike furnaces, boilers don’t have filters. However, they typically do have:
- A switch that lets you turn the unit on and off
- A temperature gauge that measures and controls the water temperature (check your boiler’s manual or ask an HVAC pro about the proper temperature range)
- A pressure gauge showing the pressure levels. (Too much or too little pressure can cause problems with your system. Check your boiler’s manual or ask an HVAC pro about the proper range.)
- A relief valve through which excess pressure safely releases
Pro tip: If there’s a leak from your boiler, you can stop its water flow by turning off your main water shut-off valve.
If your furnace or boiler runs on gas, there will be a gas shut-off valve on the gas line near the bottom of the unit. You may need to turn the gas off if there’s a gas leak or if you need to reset or do maintenance on your furnace.
A heating system that uses oil will have an oil burner to filter and ignite the oil. Burners have a filter that needs to be replaced annually.
Note: Some newer heating systems provide both heat for your home and hot water for your sinks, showers, and appliances, eliminating the need for a separate hot water heater.
Sending heat through your home
The way heat is distributed throughout your home depends on the type of heating system you have:
- Furnaces use a blower fan to blow hot air through ductwork and out of vents. Vents often have filters behind them that need to be changed every one to three months during the heating season
Ductwork often also has dampers. A damper is a valve inside the duct that opens and closes to allow air to pass through. It’s usually operated by a small handle or a wingnut on the outside of the duct, though newer systems are sometimes remotely controlled.
Dampers give you more control over your heat distribution. If you want to direct more heat to a certain air you can open the dampers and if you want to block heat from another area, you can close them.
- Boilers deliver hot water or steam through pipes to different types of radiators, including old-school cast-iron radiators and baseboard radiators
Many homes also have hydronic radiant heat in the flooring or walls. In this case, hot water is pumped through tubes under the floor or in the walls which send heat into a room.
All radiators work the same way. Hot water is pumped through them, the heat is transferred from the water to a room, and the cool water returns to the boiler.
Home heat ventilation
Good ventilation is crucial to keep your home comfortable and healthy. There are two main types: Structural ventilation and interior ventilation.
Interior ventilation includes things like bathroom exhaust fans, range hoods, and laundry ductwork.
Structural ventilation allows heat and moisture to escape from your attic, crawlspace, and/or basement to prevent rot, mold, and mildew. Vents are often found in roof eves and in the foundation.
It’s important to note that ventilation isn’t just about comfort. Blocked or damaged ventilation can impact airflow through your home, causing issues with temperature and moisture that can damage your home’s structure, roof, flooring, and drywall.
Those are the basics! With this information, you should be able to locate and identify the main parts of your HVAC system. But just like your plumbing and electrical systems, it’s probably best to leave major repairs and maintenance to the pros.
These posts offer more breakdowns of your home’s major systems:
- Furnace fundamentals: A guide to different types of home heating systems.
- The ins and outs of your home’s electrical, plumbing, and HVAC.
