Portable Air Conditioners Don't Produce Cold

Heaters work by manufacturing heat. This heat could come from a gas flame, an electrical element or the natural heat of the sun. The heat comes from somewhere, such as the chemical bonds that break as natural gas burns. Heaters inject energy into the system, which makes them functional in any environment.

Central and portable air conditioners work on a different principle. You can't "create" cold. Cold is the absence of energy and there is no efficient way to make energy disappear or go into a dormant form. Instead, portable air conditioners move the heat to another place. Ideally, they move the heat outside where it is no longer a problem for people inside the building.

The Refrigeration Cycle Explained

Portable air conditioners take advantage of the fact that when a liquid evaporates into a gas it absorbs heat and when a gas condenses back into a liquid it releases heat. This allows the fluid to act as a sort of energy sponge, soaking up heat in one place then squeezing it out in another. They use special refrigerant fluids developed for the purpose that evaporate and condense at temperatures close to room temperature.

The liquid refrigerant flows through an expansion valve into a lower pressure area of the system. The lower pressure makes it cold. Warm air from the room is blown across the pipes carrying the cold liquid, cooling the air that is blown into the room. As the liquid absorbs heat from the air, it evaporates into a gas. The gas goes through a compressor that makes it warmer. The compressed gas goes through the condenser where it releases its heat. Air blown across the condenser is exhausted outside the room carrying the heat with it. The gas condenses back into liquid and is back at the expansion valve to start the cycle over.

Side Effects of the Refrigeration Cycle

The most obvious difference between portable air conditioners and portable heaters is the air conditioners need a place to vent the undesired air. Exhaust hoses allow the hot air to be blown outside or into the building's drop ceiling, preventing it from returning to the room. Proper exhausting of the air conditioner is critical for efficient operation.

Another characteristic of portable air conditioners is they produce water. Air holds moisture -- and the amount of moisture that can be held is based on temperature. Hot air carries more moisture than cool air. As the air cools, the excess moisture condenses out. Typically this is not a lot of moisture but it can build up over time.

Once building managers understand how portable air conditioners work, they can set them up so they run as efficiently as possible.