Air conditioners work like a refrigerator which hints to why we go by refrigeration and heating, they have an indoor coil (evaporator), an outside coil (condenser), a compressor, fans (inside and outside), and a thermostat. Both the coils are like a car radiator in design with serpentine copper pipes surrounded by aluminum fins.

Typically freon is used, its the refrigerant in the system, heat is collected at the indoor coil (evaporator) and removes it to the outdoor coil (condenser) outside, keeping the indoor coil cold. The compressor that sits inside the condenser coils, forces the freon through a circuit of coils and pipes. The thermostat starts the system when temperature has risen above the set temperature, the indoor fan then blows air over the indoor coil supplying cold air and the condenser fan pulls the hot air through the outdoor coils removing heat. Heat pumps are the same when cooling.

Also like a heat pump they can come in split or packaged style. The central air conditioner (split style systems) has grills for the duct work to either supply air or return it to the air handler. The return grill will have a filter in it so that your air-handler, the indoor coil cabinet to a split system will remain clean and maintain efficiency. For package style systems all the components that are split up will be inside one metal cabinet on the roof, thats the compressor, condenser coil, and evaporator coil. Also the supply and return duct work will return to this outdoor cabinet, the ducts will stay in the attic.

(Click The Image Below To Get A Closer Look)

how air conditioner works


Energy ratings of air conditioners are based on how many BTU’s (heat) per hour the unit can remove for each watt of power it draws. The efficiency rating is called Seasonal Energy Efficiency Rating or SEER. An air conditioner with a high SEER will typically cost more, but the energy savings will make up for the higher cost. The Energy Guide label that list SEER must remain on the A/C until its sold.

Todays air conditioners are one-and-a-half times to two times more efficient than air conditioners made in the 1970’s. Listed below are the advances in HVAC technology that are the reason for the higher efficiency.

  • Variable speed or two speed blower fans
  • Copper tubing grooved inside to increase surface area
  • Aluminum fins spaced closer together and perforated (holes) to improve heat transfer to air
  • Improved electric motor design
  • Dual-speed compressor
  • Time-delay relays controlling evaporator fans


Krigger, John, and Chris Dorsi. “Chapter 8 Cooling.” Residential Energy: Cost Savings and Comfort for Existing Buildings. Ed. Mary Coster and Margaret Regan. 5th ed. Helena, MT: Saturn Resource Management, 2009. 208-10. Print.

Bowen, Scott. How HVAC system works. Digital image. Thomas HVAC Company. Thomas HVAC Company, 23 Oct. 2013. Web. 1 Feb. 2016. <>.

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