It is an event that ranks up there with the Louisiana Purchase, the Battle of Vicksburg, and the development of the atomic bomb.
At least it does according to Life magazine, which in 1975 listed the invention of air conditioning among the 100 events that most shaped America.
Introduced in 1902 as a way to control humidity in a Brooklyn printing plant, air conditioning was the brainchild of Willis Carrier, a Cornell University graduate who went on to refine his invention into a compact, practical device capable of cooling everything from movie theaters to passenger trains.
Air conditioning changed America forever.
It tamed the hottest climates, making possible the economic and population booms of the South and Southwest, and sped the growth of a host of new industries dependent on precise climate control.
Hospitals, skyscrapers and shopping malls would be unthinkable without it.
Perhaps nowhere, however, has air conditioning made so personal an impact upon American life than in the home.
In the 15 years since Life published its list of American milestones, residential air conditioning has gone from a luxury item to an expected part of daily life.
In Orange County, air conditioning for the home took off with the residential building boom of the 1970s. Industry sources estimate that 75% of the homes here are equipped with some form of refrigerated cooling device.
And yet for large numbers of homeowners, air conditioning remains something of a mystery to be misunderstood and misused--when it isn't being taken for granted, which is most of the time.
Air conditioning, whether a central system or self-contained window unit, is basically a refrigerator turned extrovert. It uses the same components (compressor, condenser, evaporator, fan and working fluid) to cool air, but on a much larger scale.
A few basic physical laws are at work. Namely, that as the working fluid (usually the chlorofluorocarbon Freon) is compressed, it gets hotter, and with the release of pressure, it evaporates into a gas and gets cooler. At the same time, hot Freon liquid releases heat to its surroundings; cool Freon gas absorbs it.
In an air conditioner, the cool gaseous Freon passes through coils in the evaporator inside the house where it absorbs heat from the warm interior air. It then passes through transfer lines to the compressor-condenser outside. Here the gas is compressed into a hot (200 degrees Fahrenheit) liquid and pumped through the condenser coils. The liquid, now being much hotter than the outside air, releases heat to its surroundings before passing back to the evaporator. As pressure is released, the liquid Freon turns once more into a cool gas, ready to begin another cycle of heat absorption and release. Put simply, an air conditioner is like a man bailing out a boat--except in this case the boat is your house, the water is heat, and the bucket is the Freon.
Many people believe that an air conditioner somehow "makes" cold air. Scientifically, however, there is no such thing as cold, only varying degrees of more or less heat. The cool breeze coming from the fan of an air conditioner is air that has lost something--about 20 degrees of heat.
As far as comfort goes, it is as important for an air conditioner to remove moisture from the air as it is to cool that air. This moisture removal is possible because the colder air becomes, the less water it can hold. As indoor air reaches its saturation point during the cooling process, the moisture it contains collects on fins inside the air conditioner and drains away. Think of how a glass of ice water "sweats" as warm air cools on contact and gives up its moisture. An air conditioner works much the same way.
The failure to understand this process of dehumidification can lead a homeowner to choose the wrong air conditioner.
Most people think bigger is better, says Mike Karsten, co-owner of Benchmark Air Systems Inc. in Anaheim. But an oversize system cools so rapidly that airborne moisture has little chance to condense on collection fins.
"People I run across in residential sales think choosing air conditioning is like buying a race car. If 200 horsepower is good, then 400 horsepower is great. That isn't the case with air conditioning. Too much cooling, too fast, and what you get is very cold damp air," Karsten says.
Most new homeowners don't have to worry about picking the right air conditioner. Builders do it for them.
"Up until the mid-1970s, (residential) air conditioning was optional," Karsten says. "Builders didn't prepare homes for it the way they do now, and often the homeowners had to buy and install their own systems."
During the "optional period" of the last 20 years, air conditioning proved popular and tens of thousands of units were installed. These are the systems that have distributors, installers and manufacturers anticipating a surge in residential sales as tired units are replaced by new, more efficient models.