Willis Haviland Carrier (November 26, 1876 – October 7, 1950) was an American engineer, best known for inventing modern air conditioning. Carrier invented the first electrical air conditioning unit in 1902. In 1915, he founded Carrier Corporation, a company specializing in the manufacture and distribution of heating, ventilation, and air conditioning (HVAC) systems.

In Buffalo, New York, on July 17, 1902, in response to an air quality problem experienced at the Sackett-Wilhelms Lithographing & Publishing Company of Brooklyn, New York, Willis Carrier submitted drawings for what became recognized as the world’s first modern air conditioning system. It was so humid that summer that the paper grew and shrank, which resulted in poor quality images, because the color printing process involved running the same piece of paper up to four times, each with a different color ink.

The 1902 installation marked the birth of air conditioning because of the addition of humidity control, which led to the recognition by authorities in the field that A/C must perform four basic functions:

1. control temperature
2. control humidity
3. control air circulation and ventilation
4. cleanse the air

After several more years of refinement and field testing, on January 2, 1906, Carrier was granted U.S. Patent 808,897 for an Apparatus for Treating Air, the world’s first spray-type air conditioning equipment. It was designed to humidify or dehumidify air, heating water for the first function and cooling it for the second.

In 1906 Carrier discovered that “constant dew-point depression provided practically constant relative humidity,” which later became known among air conditioning engineers as the “law of constant dew-point depression.” On this discovery he based the design of an automatic control system, for which he filed a patent claim on May 17, 1907. U.S. Patent 1,085,971 was issued on February 3, 1914.

In 1908, the Carrier Air Conditioner Company of America was created as a subsidiary of the Buffalo Forge Company, with Willis Carrier as its vice president.

On December 3, 1911, Carrier presented what is perhaps the most significant document ever prepared on air conditioning – Rational Psychrometric Formulae – at the annual meeting of the American Society of Mechanical Engineers. It became known as the “Magna Carta of Psychrometrics.” This document tied together the concepts of relative humidity, absolute humidity, and dew-point temperature, thus making it possible to design air-conditioning systems to precisely fit the requirements at hand.

Source: Wikipedia