How Does a Central Heat and Air System Work?

Heating Components

• The furnace serves as the "star" of the HVAC system for the home. Within it, you’ll find the main components for heating, with parts of it used when cooling the home as well. The furnace houses the burners, heat exchangers, the blower, fan and the flue. Burners deliver and burn the natural gas or propane fuel used for heating, and the exhaust fumes exit through the flue. Most HVAC systems also have a condensation tube that vents from the system outside to allow any moisture or condensation to escape.

How Heating Components Work

• While the furnace is the star of the HVAC system, the thermostat is the director and tells the furnace when to activate. Program the thermostat to set the heating unit to come on when needed. When the thermostat is on, it sends a signal to the furnace to turn on or off at preset temperatures. Burners kick on, combustion gases pass over the heat exchanger, which extracts cool air from the rooms in your home via the cold-air returns and warms the air. The heat exchanger then sends the warmed air to the blower, which blows the air into the ductwork system to vent the warm air into the home.

Air Conditioning Components

• The main components of the air-conditioning system include the compressor, the condenser and the evaporator coil. Housed in a metal-finned separate unit outdoors, you’ll find the compressor and condenser, with the evaporator coil tied to furnace function. The compressor pumps the refrigerant, typically a Freon-based chemical, through the air-conditioning system.

How Air Conditioning Components Work

• The thermostat operates in the same manner for cooling as it does in heating by sending signals to the air-conditioning components to start cooling. The cold-air return now instead draws the warm air out of the home's rooms and blows the air over the evaporator coil that contains the refrigerant. The coil transforms the heat into energy and the refrigerant chemicals cool the warm air and send the cool air through the ductwork blown by the furnace's fan to vent into the rooms of the home. Simultaneously, warm air sent to the compressor, vents outdoors, and the condenser takes the humidity and moisture from the warm air and converts it to water to also drain outdoors.

HVAC Shared Components

• The three components the heating and air conditioning system share in common are the thermostat, the furnace and the ductwork. The thermostat controls indoor temperature settings, heating and cooling periods and signals the central HVAC equipment to start operating. The furnace houses the blower and fan that pushes the warm and cool air into the ductwork. Lastly, the ductwork brings everyone in your home what they desire -- a home that’s cool in the summer and warm in the winter.