How Does an HVAC System Work? Everything You Need to Know

HVAC stands for heating, ventilation, and air conditioning, and they all sound like a cascade of complicated processes. So, that makes you wonder, how does an HVAC system work?

If you’re planning to install a new system or update your old one, it’s best if you know the components and understand how they work.


There’s no need to worry, though.

In today’s article, we’ll cover everything you need to know about how an HVAC system works. Stick around!

What Are the Components of an HVAC System?

‌HVAC systems come in different shapes and sizes. A typical HVAC system consists of a compilation of the following. For heating we have:

-Some systems use air to heat (with a furnace), and others use hot water (with a boiler or heat pump) to do this.

Thermostat: this allows you to adjust the temperature

-Ducts, vents, and blower motor: to transport hot air

-Pipes, radiators, or heat coils: to transport hot water

The cooling unit of you HVAC is basically an AC that’s composed of:

-A thermostat

-An outdoor unit that contains the fan and the condenser

-An indoor unit that contains another fan and an evaporator coil

-Copper tubes that connect both units

-Ductwork to pump the air inside your home

The Role of the Thermostat

The entire process starts with the thermostat, and it’s considered to be the main part of the HVAC system. That’s because it controls all the processes going on depending on the temperature you set.

Smart thermostats like the Google Nest Thermostat allow you to control the temperature throughout your system in a super-easy way. Smart thermostats offer mobile apps to control the temperature.

So, you can even set a timer or turn on the HVAC system before arriving at your home. Additionally, you can use voice activation to control your home settings. We have discussed how you can program a thermostat here.

It’s worth mentioning that you should check if any thermostat is compatible with your HVAC system before buying it. Sometimes you need a c-wire to install it.

How Does an HVAC System Work?

To break things down, the HVAC system works by moving the hot air from the inside of your house to the outside, or vice versa. That depends on whether you want it to heat or cool your house.

Let’s see how that happens!

How Does an HVAC System Heat Your Home?

There are three main sources for heating in an HVAC system: furnaces and heat pumps.

-Furnaces are a traditional system for heating units. They can generate heat and produce hot air through the ducts and into your home. These ducts take up quite a lot of space.

As a source of energy, the furnace might use electricity, propane, or natural gas. What’s good about furnaces is that they can do their job perfectly in icy climates.

Here’s the gist of it:

The fans take in the cool air from inside your home The air is filtered out from dust and debris

The furnace produces heat by burning its fuel or using electricity. The cool air is warmed inside the heat exchanger

Fans pump back warm air into your home through the installed duct system. The process is repeated until the required temperature is reached

Water boilers use natural gas, electricity, or propane to warm up the water. This hot water is transported through the house. A water leak in this system can cause a lot of damage. The advantage of this system is that it can generate a lot of heat and it is often used in colder climates.

– Meanwhile, a heat pump doesn’t generate warmth on its own, but it transfers the existing heat from outside to inside your home. These systems are quite new. Air-to-air and ground-to-air systems are the most popular. In the latter case, we use heat from the earth (geothermal) to heat a house.

How Does an HVAC System Cool Your Home?

Air conditioners cool the air by absorbing humidity and heat from it and releasing it outside. So, they don’t ‘generate’ cool air. The AC then pumps the cool air back into your home through the duct system.

Your AC contains a refrigerant, a chemical that cools the air passing through. So, it has a crucial role in cooling air.

Air conditioners typically have outdoor and indoor units that contain a fan. The fan takes in humid air and condensates the moisture in it through the condenser and the coils.

The process of cooling the air is simple. It consists of the following steps:

-The indoor fan takes in the hot air from your home

-The air is filtered from dust and debris

-The air passes through the refrigerant, which would be in a liquid state

-The evaporator coil absorbs the heat from the air, which turns the refrigerant into a gaseous state as it absorbs the heat

-Cool air is pumped back into your home through the ventilation system

-The hot refrigerant is transferred through the copper tubes to the compressor

-The compressor pressurizes the gas into a liquid state once again and transfers it back to the condenser coil

-The condenser coil redirects the extracted heat outside

-The process is repeated until the required temperature is reached

How Does an HVAC System Move the Air Around Your House?

The air is moved around your house through the ventilation system. Your ductwork is directly connected to the heating and cooling units in your HVAC and throughout your house.

Ventilation is crucial to your HVAC. It allows air to circulate throughout your home. Additionally, it contains filters that remove dust and debris from the air.

Inadequate ventilation and ductwork can cause an imbalance in the temperature between rooms. If that’s the case, you may notice some cold or hot spots.

The HVAC system also includes vents or chimneys to dispose of excess heat to the outside of your house.

You might have heard about ductless HVAC systems, too. Those are generally used for limited areas or single rooms. They contain an outdoor and an indoor unit, just like any HVAC system, though.


Your HVAC system is responsible for cooling, heating, and moving the air around. It can heat the air in your house by taking in the cool air, heating it, and then pumping the warm air back inside. Other systems use hot water or other liquids to heat up your home.

Cooling the air is a little more complicated. For example, you have to find the right way to run a AC condensate line.

The HVAC doesn’t generate cool air. Instead, it takes in the hot air from inside and passes it through a refrigerant. The refrigerant cools the hot air and pumps it back to your house.

We have discussed how much it costs to install an HVAC system here.

Additionally, the ventilation system’s main role is to move air throughout your home. So, it’s equally important to have an adequate ventilation system.

We have discussed the difference between Air Conditioning and refrigeration here.