Diagram of how central heating and cooling works

Central Heating & Cooling:

In summary, a central HVAC system heats or cools your home by feeding the air through your ductwork from one Central location. Getting your home to the right temperature requires a lot of moving parts that are made up of many different components. Understanding the central heating and cooling process will help you maintain your air conditioning and heating system. Knowing the basics, will help you understand what’s going on with your system every time your device starts.

How does central cooling work?

Let’s get into a little more detail of how air conditioners work. There are five main parts to an indoor and outdoor unit that work together to achieve the cool temperature in your home and these parts are: a thermostat, an outdoor unit (holds a fan, condenser, and condenser coil), an indoor unit (holds a fan and evaporator coil), copper tubes that connect the outdoor and indoor units, and ductwork throughout the home. Whenever the indoor thermostat senses the temperature that the indoor air needs to be lowered, there is a signal that is sent to the components both indoor and outdoor to start the cooling process. Then the fan from the indoor unit pulls hot air from inside of the house through return air ducts. The air is then filtered so dust, lint, and debris are taken out. The filtered warm indoor air is then blown over the cold evaporator coil. The evaporator coil absorbs the heat from the air, which converts the refrigerant into a gas. The newly cooled air is returned through the ductwork out into the various areas of your home. The heated, gaseous refrigerant that was absorbed, passes through a copper tube into the compressor in the air conditioning unit outside. The condenser coil releases the heat that used to be in your home from the refrigerant, turning it back into a liquid. The cold refrigerant then absorbs more heat from the indoor air and the cycle continues.

How does central heating work?

Central heating systems generally work in a similar way as the central cooling system by moving air around to achieve the desired temperature in your home. There are two heating system options – heat pumps and furnaces.


Heat pump system:

The system starts off by the thermostat registering the indoor temperature and kicking off the HVAC system. When the temperature in your home drops, the process essentially reverses itself. Once the function shift is registered by the heat pump, in the outdoor unit a reversing valve is turned on. The registering of the valve allows the heat pump to absorb heat energy from the outside air and transfer into the home to warm it up. The homeowner never needs to worry about the switch functions as the heat pump knows to switch on its own. 



Furnaces function in a totally different way from other HVAC products. All furnaces produce heat either from natural gas, electricity, or fuel source like propane, although they still have the thermostat that kicks off the heating process. The fuel source location which is in an outdoor unit or underground depends on the unit you have, but both are connected to your home by a pipe. 


Once the fuel source is connected, the furnace will raise the temperature in your home by first sending fuel into the furnace through the pipes and lighting the furnace burner. Cold air from your home is warmed by the fuel within the furnace heat exchanger. Through a vent, exhaust fuel from combustion is piped out. A blower fan inside the furnace directs the warmed air through the ductwork into your home. The cold air in your home is directed through the return ducts into the furnace. The process repeats itself until your desired warm temperature is achieved in your home and then the fuel switches off and the furnace stops producing heat.