Cooling Large Areas
An air conditioner was the next reasonable step after the invention of the refrigerator. Engineers looked at the basic idea of cooling the inside of a box, and wondered why the same principals couldn't cool the inside of a room. With a little tinkering of the idea the modern air conditioner was born, freeing people from the oppressive summer heat and allowing areas such as the southern and southwestern states to experience tremendous growth.
A gas that easily compresses into liquid and reverts back to gas is the key to making an air conditioner work. When the liquid changes to gas it uses the energy, or heat, from the surrounding air molecules to accomplish the task. This draws the heat from the air and allows it to flow outside with the gas. The compressor forces the gas back to a liquid form and starts the cycle all over again.
The compressor can stay on from minutes to hours, depending on the ambient air temperature and moisture level. Sometimes the compressor will cycle on an off before the air is cool, which is called short cycling. According to Jim Codd, an air conditioning technician with Air Tech Comfort in Merrillville, Indiana, there is no set time limit for a short cycle. The working definition is: if the compressor has not accomplished its task of reducing the temperature and humidity to the level the control is set at before stopping, then it has short cycled. It usually isn't noticed unless it happens quickly several times in a row.
An over-sized AC unit can become easily confused as it puts out a lot of cold air in a short time in a small space, which then causes the controls to think the overall temperature has dropped to a sufficient level. The compressor shuts down within a few minutes, only to start back up again after another three to four minutes when the controls determine the correct temperature. This off-on-off-on can continue for a while, which may damage the compressor from the constant short cycling.