What Makes Air Conditioning Work?


A simplified rule of thumb – Get all the facts about your home & climate from your contractor.

This is just for general estimating purposes.

  • 1 Ton of air conditioning (12,000 BTU Cooling) for every 500 square feet of living space.
  • 2,000 sq. ft. divided by 500 sq. ft. = about 4 Tons of A/C

This assumes some basic values, such as:

  • Standard 8 foot ceilings.
  • South facing walls are less than 20% windows.
  • Windows have drapes or other coverings.
  • Walls and attic spaces are insulated.

Air conditioning is really pretty simple when you get down to the basics. It is a sealed system composed of copper tubing, some electronics, and three basic components: A compressor and two heat exchangers or coils. The cycle goes like this:

  • The compressor (1) compresses the refrigerant into high pressure vapor.
  • The refrigerant vapor enters the outside coil (condenser) (2) where a fan (3) blows air across it. This cools the refrigerant by removing heat (4) and condenses it to liquid. This is the same as when steam is cooled. It will condense into liquid refrigerant.
  • The refrigerant which is now liquid (5) is pushed along the refrigerant line to the inside coil (evaporator) where it encounters a metering device.
  • The metering device (6) limits the amount of refrigerant entering the inside coil (evaporator) and creates a pressure drop across it.
  • This allows the refrigerant to expand from a small diameter tube to a larger one.
  • At this coil a fan (3) blows air across it and the refrigerant absorbs the heat in the air. This effectively cools the air exiting the coil (7) and the heat evaporates the refrigerant back to vapor.
  • From here the refrigerant vapor (8) returns to the compressor to start the cycle over again.
  • So to summarize, the air releases heat energy to the refrigerant (cooling the air) at the inside coil (evaporator) and the refrigerant releases that heat energy into the air at the outside coil (condenser).