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Air Conditioners, HVAC Education, Packaged Products, Indoor Air Quality

What is Central Air and How Does It Work?

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.

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There are two different types of central air conditioners—split 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.

How does an 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.

What is included in 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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