Central Heating and Cooling Systems: What is It & How Does It Work?

how hvac works

Jake Smith, Online Marketing Strategist
Technically Reviewed by Jake Smith, Online Marketing Strategist on Sep 28, 2022 | Written by Alpha Mechanical Editorial Contributors

How does an HVAC system work?

In the midst of all the changing seasons, you may be asking yourself how do air conditioning systems work or should my home have a heat pump or furnace for our region? In this article we dive deep into how does a home HVAC system work, the options you have for cooling and heating systems and the process of how each unit functions and in which climate. Read on to get an overview of HVAC system working through and through and your steps for planning your new installation or HVAC replacement process.

Central heating and cooling

The overall function of a central HVAC system is to heat or cool your home by supplying heated or cooled air through your ductwork. While the operation seems simple, getting your home to desired set temperature requires a lot of moving parts with each component playing a role in the process.

Learning how the HVAC units function in your home will allow you to maintain your systems better. Once you know the basic processes, you’ll be in the know about what is happening when you hear your system turn on.

How does air conditioning work in a house?

Air conditioners operate by taking in the hot and humid air from your home and releasing it outside with the intent to drop the temperature in your home. In order to function efficiently in this process, all parts of the central cooling system must work together.

Central cooling system options

In most cases, central air conditioning refers to a split-system air conditioner or a heat pump. Both a split-system and a heat pump have a unit inside and outside of the home. The indoor and outdoor units collaborate to deliver cool air through the ductwork system in your home.

Together, they are composed of five main parts: a Thermostat → an Outdoor Unit (which has a fan, condenser, and condenser coil) → an Indoor Unit (which holds a fan and evaporator coil) → Copper Tubes that join together the outdoor and indoor units → and a System of Ducts throughout the home for distribution.

While a split-system AC only cools, a heat pump can reverse the flow of refrigerant to be used as a heater, in which case the process works in reverse.

A packaged air conditioner is the final type of central cooling. A packaged unit holds the same functions as a split system AC or heat pump with the same parts as well, the main exception is that the whole unit sits outside the house; there is no equipment inside the home. The packaged unit takes air from your house through the return ductwork, chills it, and then feeds it back to the house through a second set of ductworks, called the supply ductwork.

workings of hvac

Central cooling process

Central cooling begins when a thermostat senses that the temperature in your home needs to be changed because it is warmer than the set temperature on the device. In the case of central cooling, the thermostat will notify the air conditioning unit that the temperature is too warm and all parts will kick on to work simultaneously to get your home to the right temperature for your home. Once the systems are alerted, these are the following steps taken to cool your home:

  1. A fan from the indoor portion of your AC moves room temperature hot air outside of your home.
  2. Dust, lint, and debris is then filtered and removed from the air.
  3. The filtered, hot air is blown over the evaporator coil, a portion of your air conditioner that gets filled with liquid refrigerant. The evaporator coil depletes the heat from the air, which turns the coolant liquid into a gas.
  4. The newly cooled air is supplied back into your home via ducts.
  5. While that cool air is being put into your home, the heat that was recently absorbed through the evaporator coil, passes through a copper tube into the outdoor portion of your outdoor air conditioner unit.
  6. The refrigerant is put into the compressor, which pressurizes the gas and sends it to the condenser coil.
  7. The condenser coil delivers the heat that used to be in your home from the refrigerant, which turns it back into a liquid.
  8. The process starts again.

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How does central heating work?

Central heating systems can work in a similar way as central cooling units by moving air around to bring the desired temperature to the home. Instead of moving hot air out, central heating systems move hot air in to get your home to your desired temperature, although the process is different amongst the different heating units. Depending on which central heating system you own, your HVAC device might actually be producing its own heat.

Central heating system options

The two main options for central heating systems that we will be discussing: heat pumps and furnaces.


Furnaces work by burning a natural fuel source to make heat from scratch and then distribute that heat through ducts. Furnaces work the best when the temperature outside is really low (below 50°F), because they produce hot heat at a relatively fast pace. Furnaces are primarily uncommon and unnecessary in the southern regions of the country. If you are in need of furnace installation in Sacramento, give Alpha Mechanical a call and our team will get you on the books to bring efficient heat to your home.

Heat Pump:

Heat pumps work throughout the year in all temperatures and can switch between heating and cooling functions depending on the temperature. Heat pumps are ideal for a variety of climates because they can heat and cool under any circumstances although they are mainly found in climates that do not go below 50 degrees Fahrenheit.


Central heating process

All central heating processes start the same way central cooling processes do: through the thermostat. The thermostat is the brains of the HVAC system and it signals to the other unit that the temperature needs to be adjusted which kick starts the HVAC system.

Heat pumps have the same parts as a split-system air conditioner and work in the same way when they’re needed for cooling. When the temperature drops and a heat pump needs to create heated air, the entire process essentially reverses itself. A heat pump has a feature called a reversing valve in the outdoor unit that turns on and the heat pump shifts its function to heating. The heat pump absorbs heat energy from the outside air and transfers it inside the home rather than taking heat from the home and putting it outside to cool it down. The reversing valve on a heat pump works on its own and is never something the homeowner has to manually switch.

Furnaces, on the other hand, function in a totally different way than other HVAC products. While the thermostat still triggers the unit to start the heating process, all furnaces produce heat from either natural gas, electricity, or fuel oil source, like propane. Depending on the type of furnace your home has, the fuel source can be held in an outdoor unit or underground, either way the fuel source is connected to your home through a pipe. The fuel source is one of the main parts in the heating up process. Once your fuel source is connected and your unit is alerted to turn on, the furnace follows these steps to raise the temperature:

  1. Fuel comes into the furnace from the outside unit through the pipe and lights the furnace burner.
  2. Cold air from your home is warmed via the fuel within the furnace heat exchanger.
  3. Exhaust fuel from combustion is piped out of the furnace through a vent ensuring it does not come into your home.
  4. A blower fan inside the furnace directs the newly warmed air through the duct in each room in your home.
  5. More cold air is directed from your home into the furnace via the return ducts.
  6. The process repeats itself until your home is warmed and brought to the desired temperature and the fuel switches off and the furnace stops supplying heat.

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What steps should homeowners take before installation?

Step 1: Determine your heating and cooling needs

If the place where you live drops to freezing temperatures often in the winter season, consider investing in a furnace to ensure a hot, dry heat quickly to your home. If the temperatures where you live consistently remain mild for the majority of the year, a heat pump may be the better fit for your home. Assess your HVAC needs based on your geographic location, yearly temperature patterns, and the size of your home to be sure you’re installing the right unit.

Step 2: Hire a licensed HVAC professional for Installation

Most new HVAC devices take a few hours to up-to a day to install. In the case of a furnace installation, a technician will have to arrange for a fuel source to be installed if there is not currently one for your home which could prolong the process a bit. Choosing an HVAC technician in your area is the best way to guarantee the installation is done right. Your HVAC specialist will install the system and be there to help with maintenance/troubleshooting when that may become necessary.

Consider Alpha Mechanical

Alpha Mechanical has been in business in the Sacramento area for many years. We are committed to providing exceptional service to our customers.We never seek to upsell unnecessary equipment or rip off our customers financially when it comes to their HVAC units. Our technicians know how to improve the efficiency of the air conditioning system and help you save money in the process.

We offer coupons and financing for your convenience through partnered banks. We take time to communicate to our customers the problem with the furnace and guide them to optimal and reasonable solutions at a competitive price.

Final Thoughts

Air conditioning and heating for your home has many moving parts that work together to supply your home with your desired temperature. The main equipment parts that apply to each system are a thermostat, indoor unit and an outdoor unit, tubing that joins the units together and ductwork that supplies the air throughout your home.

Although this article covers how residential air conditioning works, Alpha Mechanical is a NATE certified HVAC professional providing residential and commercial HVAC service in Sacramento.

Contact us 916.848.5980 and we will get your HVAC system back online.

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Frequently Asked Questions

Frequently Asked Questions

How do heating and cooling coils work?

The coils featured in a heat pump for heating and cooling purposes exist to either absorb the heat from the air to turn it into a gas or a liquid depending on whether the coil is in the inside or outside unit.

Does an HVAC system heat and cool?

Although there are several types of heating and cooling system options, the unit that can serve as a heater and an air conditioner is the heat pump, primarily used in geographical locations that do not reach freezing temperatures.

What are the different types of HVAC systems?

For cooling: Split-system air conditioner, heat pump or packaged air conditioner.

For heating: heat pump and furnace are the main two choices.

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