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Air Conditioners, HVAC Education, Indoor Air Quality

What is Central Air Conditioning and How Does Central Air Work?

How does air conditioning work in a central air system? Central air conditioning is a common term used to describe most whole-home air conditioning systems. It replaces warm air with cool air that’s been passed over cold coils, then pushes it into your living spaces. There are two different types of central air conditionerssplit systems and packaged systems. A split system has both an indoor and outdoor unit, while a packaged system is contained in a single outdoor unit to help when there is limited space.

two boys play in a tent in a home with a central air conditioning system

How does a central air conditioner work?

  • When the indoor temperature rises above your desired set point, the thermostat turns on the system.
  • The fan in the indoor unit pulls warm air from inside your home into return air ducts, then passes it through filters to remove dust and airborne pollutants.
  • That air passes over the cold evaporator coil, where liquid refrigerant absorbs heat, changes it into a gas refrigerant, and cools the air.
  • The blower fan then sends the cooled air into living spaces.
  • The now-warm gas refrigerant travels to the compressor through copper tubing.
  • The compressor pressurizes the gas and sends it to the condenser coil, which releases the heat outdoors and turns the refrigerant back to liquid.
  • The refrigerant travels to the evaporator coil to continue the cycle.

Parts of a Central Air Conditioning System

  • Both a split system and a packaged system use a thermostat to control the temperature and ductwork to circulate air around the indoor living spaces
  • In a split system:
    • Outdoor unit—fan, condenser coil, and compressor
    • Indoor unit—furnace or fan coil, which houses the evaporator coil and fan to circulate cool air
    • Copper tubing—where the refrigerant flows between the indoor and outdoor units
  • In a packaged system:
    • Fan, condenser coil, compressor, and fan coil—all in one unit
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